NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts

NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts

In this chapter, students will understand the chemical properties of acids, and bases, how acids and bases react with metals, how metal carbonates, and metal hydrogen carbonates react with acids, how acids and bases react with each other, the reaction of metallic oxides with acids. Students will also learn about what all acids and bases have in common, what happens to acids and bases in water solution, the importance of pH in everyday life, pH of salts.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 2 – Acids, Bases and Salts solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 2 – Acids, Bases and Salts Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 2 In Text Book Questions

Question 1.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution respectively. If you are given only red litmus paper, how will you identify the contents of each test tube ?
Answer:
Take a small volume of all the three liquids in three test tubes. Dip red litmus paper strips separately in all the three. The tube in which red litmus strip turns blue, contains basic solution. Now remove the blue litmus paper and dip it one of the remaining test tubes. If the colour of the blue litmus paper changes to red, the tube contains acidic solution. In case, it remains blue then the tube contains distilled water.

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Question 2.
Why should not curd and sour substances be kept in containers made up of brass or copper ?
Answer:
Both curd and sour substances contain some acids in them. They react with copper or brass vessels to form certain salts which are of poisonous nature. Therefore, it is not advisable to keep them in these containers.

Question 3.
Which gas is usually liberated when an acid reacts with a metal ? Illustrate with an example. How will you test the presence of this gas ?
Answer:
Metals are mostly reactive in nature. They react with dilute acids (HCl and H2SO4) to evolve hydrogen gas. For example,
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 1
The gas burns with a pop sound when a burning candle is brought near it.

Question 4.
A metallic compound ‘A’ reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer:
Since the gas is evolved with effervescence and extinguishes fire, it is expected to be CO2 gas. As calcium chloride is formed as one of the products, this means that the substance A’ can be calcium carbonate. It reacts with dilute hydrochloric acid as :
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 2

Question 5.
Aqueous solutions of HCl, HNO3 and H2SO4 etc. show acidic character while those of the compounds like ethyl alcohol (C2H5OH) and glucose (C6H12O6) fail to do so. Explain.
Answer:
All the acids that are listed, have replaceable hydrogen atoms which they release in aqueous solution as H+ ions. Therefore, they show acidic character. However, both ethyl alcohol (C2H5OH) and glucose (C6H12O6) do not have replaceable hydrogen atoms. They fail to evolve hydrogen gas and do not show any acidic character.

Question 6.
Why does aqueous solution of an acid (HA) conduct electricity ?
Answer:
Aqueous solution of an acid (HA) releases H+ ions or H3O+ ions and anions (A) in solution. Since ions are the carrier of charge, the aqueous solution of an acid conducts electricity.

Question 7.
Why does not dry HCl gas change the colour of the dry litmus paper ? (CBSE 2013)
Answer:
Dry HCl gas fails to release any H+ ions which means that it is not acidic. It fails to change the colour of the dry litmus paper which has also no moisture present.

Question 8.
While diluting an acid, why is it not recommended that acid should be added to water and not water to the acid ? (CBSE 2011)
Answer:
Acids particularly the mineral acids like H2SO4, HNO3 and HCl etc., have strong affinity for water. The dilution process is highly exothermic in nature. The heat evolved may crack or break the container and may also convert the acid into fog which is likely to pollute the atmosphere. In order to control the heat evolved, it is advisable to add acid drop by drop to water. In case water is added to acid, then the entire acid will get itself involved in the exothermic process. It may not be possible to control the heat evolved.

Question 9.
How is concentration of hydronium ions (H3O+) affected when solution of an acid is diluted with water ?
Answer:
An acid dissociates into hydronium ions (H3O+) and anions when dissolved in water. Upon dilution, the volume of the solution increases and the number of ions per unit volume decreases. Therefore, the concentration of H3O+ ions per unit volume decreases.

Question 10.
How is concentration of hydroxyl (OH) ions affected when excess of base is dissolved in solution of sodium hydroxide ?
Answer:
Sodium hydroxide (NaOH) is a strong base. It immediately dissociates in solution to give OH ions and cations. Upon dissolving more of base in the solution, the concentration of OH ions further increases.

Question 11.
You have two solutions A and B. The pH of solution A is 6 and that of solution B is 8. Which solution has more hydrogen ion concentration ? Which of these is acidic and which one is basic ?
Answer:
The pH of a solution is inversely proportional to the concentration of H+ ions in solution. Lesser the pH of the solution, more will be the H+ ion concentration. The solution A with pH 6 has more H+ ion concentration than the solution with pH equal to 8. The solution A is acidic because its pH is less than 7 and the solution B is basic because its pH is more than 7.

Question 12.
What effect does concentration of H+(aq) ions have on acidic nature of absolution ?
Answer:
The acidic nature of a solution is directly related to the concentration of H+ ions. As the concentration of H+ ions increases, the acidic nature of solution also increases.

Question 13.
Do basic solutions also have H+(aq) ions ? If yes, then why are these basic ?
Answer:
Yes, basic solutions have also H+(aq) ions present in them. Actually, these solutions are prepared in water. Being a weak electrolyte, it dissociates to give H+ and OH ions. However, the number of H+ ions is very small as compared to the number of OH ions which are released by the base and also by water. Therefore, the solutions as a whole are of basic nature.

Question 14.
Under what soil conditions, do you think a farmer would spread or treat the soil of his fields with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate) ?
Answer:
A soil usually becomes acidic when there is either a high peat content, iron minerals or there is some rotting vegetable. In order to reduce the acidic strength, ‘liming of soil’ is usually done. For this, any of the substances that have been mentioned are added to the soil since these are of basic nature.

Question 15.
Name the substance which upon treating with chlorine gives bleaching powder. Write the chemical equation for the reaction. (CBSE 2011)
Answer:
Slaked lime is the substance which reacts with chlorine to give bleaching powder
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 3

Question 16.
Name the sodium compound used for softening hard water.
Answer:
Washing soda or sodium carbonate. It is chemically sodium carbonate decahydrate (Na2CO3.10H2O). What will happen if the solution of sodium hydrogen carbonate is heated ?

Question 17.
Write the chemical equation involved.
Answer:
Carbon dioxide gas will evolve and sodium carbonate will be left.
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 4

Question 18.
Write the chemical equation for the reaction between Plaster of Paris and water.
Answer:
study rankers class 10 science Chapter 2 Acids Bases and Salts 5

NCERT Solutions for Class 10 Science Chapter 2 NCERT End Exercise

Question 1.
A solution turns red litmus blue. Its pH is likely to be
(a) 2
(b) 4
(c) 7
(d) 10.
Answer:
The solution is basic. Its pH is likely to be 10.
Therefore, (d) is the correct answer.

Question 2.
A solution reacts with crushed egg-shells to give a gas that turns lime water milky. The solution contains
(a) NaCl
(b) HCl
(c) LiCl
(d) KCl.
Answer:
The crushed egg-shells consist of layer of calcium carbonate which reacts with dilute HCl to evolve CO2(g). The gas turns lime water milky.
Therefore (b) is the correct choice.

Question 3.
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the volume of HCl solution (the same solution as before) required to neutralise will be
(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL.
Answer:
10 mL of NaOH will require HCl = 8 mL and 20 mL of NaOH will require HCl=16 mL.
Therefore, (d) is the correct answer.

Question 4.
Which of the following types of medicines is used for treating indigestion ?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic.
Answer:
Antacid is used for treating indigestion.
The correct answer is (c).

Question 5.
Write the word equations and the balanced equations for the reactions when :
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminium powder.
(d) dilute hydrochloric acid reacts with iron fillings.
(d) dilute hydrochloric acid reacts with iron fillings.
Answer:
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 6

Question 6.
Compounds like alcohol and glucose also contain hydrogen but are not characterised as acids. Describe an activity to prove it.
The chemical formula of ethyl alcohol is C2H5OH which is an alcohol and of glucose is C6H12O6. Both are organic compounds and contain hydrogen atoms. However, they do not behave as acids. (CBSE 2011, 2013)
Answer:
This can be shown by the following activity :
In a glass beaker, take a dilute solution of glucose (C6H12O6). Fix two small nails of iron in a rubber cork and place the cork in the beaker as shown in the figure. Connect the nails to the terminals of a 6 volt battery through a bulb. Switch on the current. The bulb will not glow. This shows that the electric current has not passed through the glucose solution. As the current is carried by the movement of ions, this shows that in solution, glucose has not given any H+ ions.
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 7
Now repeat the same experiment with ethyl alcohol (C2H5OH). The bulb will not glow in this case also. This shows that both of them do not behave as acids although they contain hydrogen atoms in their molecules.

Question 7.
Why does not distilled water conduct electricity whereas rain water does ?
Answer:
Pure water (or distilled water) is a very weak electrolyte and does not dissociate into ions. Therefore, it does not conduct electricity. However, rain water contains some dissolved acids like carbonic acid (H2CO3) and sulphurous acid (H2SO3). Actually air contains traces of both CO2 and SO2 gases which dissolve in rain water to produce corresponding acids. As a result, water becomes acidulated and gets ionised easily. Therefore, rain water conducts electricity.

Question 8.
Why does not an acid show any acidic behaviour in the absence of water ?
Answer:
An acid gets ionized only in aqueous solution i.e. in the presence of water. In other words, an acid releases H+ ions or shows acidic behaviour only in the presence of water.

Question 9.
Five solutions A, B, C, D and E when tested with universal indicator show pH as 4, 2, 12, 7 and 9 respectively. Which solution is :
(a) neutral
(b) strongly alkaline
(c) strongly acidic
(d) weakly alkaline
(e) weakly acidic
(f) Arrange the pH in increasing order of H+ ion concentration.
Answer:
(a) Neutral : D with pH = 7
(b) Strongly alkaline : C with pH = 12
(c) Strongly acidic : B with pH =2
(d) Weakly alkaline : E with pH = 9
(e) Weakly acidic : A with pH = 4
(f) Increasing order of H+ ions concentration :C<E<D<A<B

Question 10.
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A while acetic acid (CH3COOH) is added to test tube B. In which case, fizzing occurs more vigorously and why ?
Answer:
Fizzing in the reaction is due to the evolution of hydrogen gas by the action of metal on the acid
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 8
Since hydrochloric acid is a stronger acid than acetic acid, fizzing occurs more readily in tube A than in tube B. Actually hydrogen gas will evolve at more brisk speed in test tube A.

Question 11.
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd ? Explain your answer. (CBSE 2011)
Answer:
When milk changes into curd, the pH decreases. Actually, lactose (carbohydrate) present in milk gets converted into lactic acid. As more of acid is formed, pH of the medium decreases.

Question 12.
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline ?
(b) Why does this milk take a long time to set as curd ? (CBSE 2011)
Answer:
(a) We know that fesh milk is slightly acidic due to presence of lactic acid and its pH is 6. Upon
standing, its pH slowly decreases and it becomes sour since more of acid to released. The purpose of adding baking soda or sodium hydrogen carbonate (NaHCO3) is to make medium slighly alkaline. The base released will neutralise the effect of lactic acid present in milk. This will check the milk from getting sour.
(b) When milk sets as curd, it becomes more acidic and pH decreases. In the alkaline medium, it takes longer time to achieve acidic medium back so that milk may set as curd.

Question 13.
Why should Plaster of Paris be stored in a moisture-proof container ?
Answer:
In the presence of moisture, Plaster of Paris gets hydrated and changes to Gypsum which is a hard mass.
NCERT Solutions for Class 10 Science Chapter 2 Acids Bases and Salts 9
It can be no longer be used for making moulds and statues. Therefore, Plaster of Paris is kept in moisture proof containers or bags.

Question 14.
What is neutralisation reaction ? Give two examples.
Answer:
Neutralisation reaction is the reaction between acid and base dissolved in aqueous solution to form salt and water.
study rankers class 10 science Chapter 2 Acids Bases and Salts 10

Question 15.
Both NaCl and KNO3 are neutral in nature. They neither change blue litmus red nor red litmus blue. That is why the reaction is called neutralisation reaction.
Give two important uses of washing soda and baking soda. (CBSE 2011)
Answer:
Uses of washing soda:

  1. In the manufacture of glass, soap, paper and chemicals like caustic soda (NaOH) and borax (Na2B4O7) etc.
  2. As a cleansing agent for domestic purposes.

Uses of baking soda:

  1. In baking powder used for preparing cakes.
  2. In antacids to reduce acidity in the stomach.

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

In this chapter, students will learn about the physical properties of metals, and non-metals, chemical properties of metals, how metals react with air, water, acid, other solutions, and metal salts, reactivity series.

Further students will come to know how metals and non-metals react, properties of ionic compounds, the occurrence of metals, extraction of metals, refining of metals, corrosion, prevention of corrosion. The chapter contains questions and answers exercise along with multiple choice questions.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 3 – Metals and Non-metals solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 3 – Metals and Non-metals Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 3 NCERT Questions

NCERT Solutions for Class 10 Science Chapter 3 In Text Book Questions

Question 1.
Give example of a metal which
(a) is a liquid at room temperature
(b) can be easily cut with a knife
(c) is the best conductor of heat
(d) is the poorest conductor of heat.
Answer:
(a) Mercury
(b) Sodium
(c) Silver
(d) Lead.

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Question 2.
Explain the meaning of malleable and ductile.
Answer:
Malleable: The property due to which a substance can be beaten into sheets is known as malleability. Metals are malleable in nature.
Ductile. The property due to which a substance can be drawn into wires is known as ductility. Metals are ductile in nature.

Question 3.
Why is sodium kept immersed in kerosene oil ? (CBSE 2011)
Answer:
Sodium reacts with air and water both. It is a highly reactive metal. When kept in open, it readily combines with oxygen present in air to form its oxide. Similarly, it reacts with water vapours or moisture to form sodium hydroxide.
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 1
In order to preserve sodium metal, we generally keep it under kerosene so that neither air nor moisture may come in its contact.

Question 4.
Write the equations for the reactions of
(a) iron with steam
(b) calcium with water
(c) potassium with water.
Answer:
(a) 3Fe(s) + 4H2O (steam) ———–> Fe3O4(s) + 4H2(g)
(b) Ca(s) + 2H2O(aq) ———–> Ca(OH)2(s) +H2(g)
(c) 2K(s) + 2H2O(aq) ———–> 2KOH(aq) + H2(g)

Question 5.
Samples of four metals A, B, C and D were taken and were added to the following solutions one by one. The results obtained have been tabulated as follows :

Metal

Solution to which metal is added

Iron(II) sulphate

Copper(II) sulphate Zinc sulphate

Silver nitrate

A

No reaction Displacement

B

Displacement No reaction „
C No reaction No reaction No reaction

Displacement

D No reaction No reaction No reaction

No reaction

Use the table given above to answer the following questions :
(a) Which is the most reactive metal ?
(b) What would you observe when B is added to solution of copper(II) sulphate ?
(c) Arrange the metals A, B, C and D in order of increasing reactivity. (CBSE 2011)
Answer:
Based on the activity series, the relative position of the metals in which involved in solutions is : Zn > Fe > Cu > Ag. On the basis of the results given in the table .

  • Metal A is more reactive than copper and less reactive than iron.
  • Metal B is more reactive than iron and less reactive than zinc. –
  • Metal C is only more reactive than silver and less reactive than other metals.
  • Metal D is the least reactive in nature.

In the light of above information, we can conclude that
(a) Metal B is the most reactive.
(b) Since B is more reactive than iron, it is also more reactive than copper. This means that it would displace copper from copper(II) sulphate solution. The blue colour of solution will slowly fade.
(c) The decreasing order of reactivity of metals is: B>A>C>D.

Question 6.
Which gas is produced when a reactive metal reacts with dilute hydrochloric acid ? Write the chemical reaction when iron reacts with dilute H2SO4. (CBSE 2010)
Answer:
Hydrogen gas (H2) is produced when a reactive metal reacts with dilute hydrochloric acid. Iron and dilute H2SO4 react as follows :
Fe(s) + H2SO4(aq) ————> FeSO4(aq) + H2(g)
Hydrogen gas is evolved in this reaction also.

Question 7.
What would you observe when zinc is added to a solution of iron (II) sulphate ? Write the chemical reaction that takes place. (CBSE 2010)
Answer:
The green colour of the solution would slowly disappear. Zinc would gradually dissolve and iron would get precipitated at the bottom of the beaker.
vedantu class 10 science Chapter 3 Metals and Non-metals 2

Question 8.
(i) Write electron-dot structures for sodium, magnesium and oxygen.
(ii) Show the formation of Na2O and MgO by the transfer of electrons.
(iii) What are the ions present in these compounds ?
Answer:
(i)
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 3
(ii) Formation of sodium oxide (Na2O)
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 4
Formation of magnesium oxide (MgO)
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 5
(iii) For answer, consult structures given above.

Question 9.
Why do ionic compounds have high melting points ? (CBSE 2014)
Answer:
In the formation of ionic compounds, positive ions (cations) and negative ions (anions) participate. These are closely packed and the ionic compounds exist as crystalline solids. They have strong inter ionic forces of attraction and have high melting and boiling points.

Question 10.
Define the following terms :

  1. Minerals
  2. Ores
  3. Gangue.

Answer:

  1. Minerals : These are the combined states of metals and non-metals present in earth’s curst.
  2. Ores : The minerals from which metals can be conveniently and profitably extracted, are called ores.
  3. Gangue : It represents the earthy impurities such as mud, sand and clay associated with the ore.

Question 11.
Name two metals which are formed in nature in free state.
Answer:
The metals are gold (Au) and platinum (Pt).

Question 12.
Which chemical process is used for obtaining a metal from its oxide ?
Answer:
The chemical process is known as reduction.

Question 13.
Metallic oxides of zinc, magnesium and copper were heated with the following metals. In which cases, will you find displacement reactions taking place ?

Metal

Zinc Magnesium

Copper

Zinc oxide

Magnesium oxide

Copper oxide

Relative positions of these metals in the activity series are : Mg, Zn, Cu : In the light of this :
Answer:
Magnesium (Mg) will displace both zinc (Zn) and copper (Cu) from their oxides
Mg + ZnO ———-> MgO + Zn
Mg + CuO ———-> MgO + Cu
Zinc will displace copper from copper oxide.
Zn + CuO ———–> ZnO + Cu
Copper is least reactive and will not initiate displacement reaction.

Question 14.
Which metals do not corrode easily ?
Answer:
Metals such as gold (Au) and platinum (Pt) present at the bottom of the activity series do not corrode easily.

Question 15.
What are alloys ? (CBSE 2011)
Answer:
Alloys are the homogeneous mixture of two or more metals or even metals and non-metals.

NCERT Solutions for Class 10 Science Chapter 3 NCERT End Exercise

Question 1.
Which of the following will give displacement reactions ?
(a) NaCl solution and copper metal
(b) MgCl2 solution and aluminium metal
(c) FeSO4 solution and silver metal
(d) AgNO3 solution and copper metal.
Answer:
(d). Only AgNO3 solution will give displacement reaction with copper (Cu) because copper is placed above silver in the activity series.

Question 2.
Which of the following methods is suitable for preventing an iron frying pan from rusting ?
(a) applying grease
(b) applying paint
(c) applying a coating of zinc
(d) all the above.
Answer:
Theoretically all the three methods are helpful for preventing an iron frying pan from rusting. However, the constituents of both grease and paint are mostly organic compounds. They cannot withstand the heat and do not last. Therefore, applying a coating of zinc (galvanisation) is the best method. Option (c) is correct.

Question 3.
An element reacts with oxygen to give a compound with high melting point. This compound is also water soluble. The element is likely to be :
(a) Calcium
(b) Carbon
(c) Silicon
(d) Iron
Answer:
(a). Calcium (Ca) combines with oxygen to form calcium oxide (CaO) with very high melting point. CaO dissolves in water to form calcium hydroxide
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 6

Question 4.
Food cans are coated with tin and not with zinc because
(a) Zinc is costlier than tin
(b) Zinc has higher melting point than tin
(c) Zinc is more reactive than tin
(d) Zinc is less reactive than tin.
Answer:
(c). Zinc is more reactive than tin and reacts with organic acids present in food to form poisonous compounds. Since tin is placed below zinc in the activity series, it is less reactive and does not react with the organic acids. Therefore, (c) is the correct option.

Question 5.
You are given a hammer, a battery, a bulb, wires and a switch :
(a) Flow could you use them to distinguish between samples of metals and non metals ?
(b) Assess the usefulness of these tests to distinguish between metals and non metals.
Answer:
(a) With the help of hammer, convert both the metal and non-metal (solid) in the form of plates or rods. Metal will readily form these since they are malleable. Non-metals being brittle will break when struck with hammer. They will form plates with difficulty Now construct a cell in both the cases using these plates as electrodes and switch on the current. If the bulb glows, this means that the electrodes are of metals. In case, this does not glow, this means that the electrodes are of non-metals.
(b) From these tests, we may conclude that

  1. Metals are malleable while non-metals are not.
  2. Metals are good conductors of electricity while non-meals are not (graphite is an exception).

Question 6.
What are amphoteric oxides ? Give examples of two amphoteric oxides.
Answer:
These are the oxides which can act both as acids and bases. For example, aluminium oxide (Al2O3) and zinc oxide (ZnO). The amphoteric character of the two oxides are shown by the following reactions.
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 7

Question 7.
Name two metals which can displace hydrogen from dilute acids and two metals which can not do so.
Answer:
Sodium and calcium can displace hydrogen from dilute acids Copper and silver can not displace hydrogen from dilute acids.

Question 8.
In the electrolytic refining of metal M, name anode, cathode and electrolyte.
Answer:
Anode : Rod of the impure metal
Cathode : Rod of pure metal
Electrolyte : Aqueous solution of soluble salt of metal M.

Question 9.
Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in the figure.
vedantu class 10 science Chapter 3 Metals and Non-metals 8
What will be the action of gas on

  1. dry litmus paper ?
  2. moist litmus paper ?

Write a balanced chemical equation for the reaction taking place.
(CBSE 2011)
Answer:
The gas evolved upon heating sulphur powder on a spatula is sulphur dioxide
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 9

  1. SO2(g) has no action of dry litmus paper.
  2. SO2(g) dissolves in moisture (water) present in moist litmus paper to form sulphurous acid. In acidic solution, moist litmus paper will change to red.
    NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 10

Question 10.
State two ways to prevent the rusting of iron.
Answer:

  1. By applying a coating of grease or paint on the surface of iron.
  2. By depositing a layer of zinc on the surface of iron. The process is called galvanisation.

Question 11.
What types of oxides are formed when non-metals combine with oxygen ?
Answer:
The oxides are generally acidic in nature which means that when dissolved in water, their solutions change blue litmus to red. For example,
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 11

Question 12.
Give reasons for the following :
(a) Platinum, gold and silver are used to make jewellery.
(b) Sodium, potassium and lithium are stored under oil.
(c) Aluminium is a highly reactive metal but still used for making cooking utensils.
(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction. (CBSE 2013, 2014)
Answer:
(a) These metals placed at the bottom of the activity series are very little reactive in nature. Gold and
platinum are known as noble metals. They are not affected by air, water and by chemicals. Since they have bright lustre, jewellery can be made from these metals.
(b) There are reactive metals placed high in the activity series. In air, their surface gets tarnished due to presence oxygen, water vapours and carbon dioxide in air. With water, these react violently to evolve so much heat that is not possible to handle them. These metals are generally kept under kerosene which does not contain air and water.
(c) When exposed to air, the metal changes its oxide called aluminium oxide (Al2CO3). It gets deposited over the surface of the metal and forms a protective coating on the surface. Due to the presence of this layer, the metal becomes unreactive and can be used in making cooking utensils.
(d) Both carbonate and sulphide ores of metals cannot be directly reduced to metallic state. Flowever, metal oxides can be easily reduced with coke or other reducing agents. Both are therefore, converted into their respective oxides by calcination process (for carbonate ores) and by roasting process (for sulphide ores).
Metal oxides can be easily reduced to metallic form with coke (C) or any other suitable reducing agent. Therefore, carbonates and sulphides are converted to the oxide form by processes of calcination and roasting and are not directly reduced.

Question 13.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels. (CBSE 2014)
Answer:
Copper metal slowly reacts with water, carbon dioxide and oxygen present in air to form basic copper carbonate which is green in colour. Its layer slowly gets deposited on the surface of the metal. Now lemon
NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals 12
juice contains citric acid while tartaric acid is present is tamrind. Both these acids react with basic copper carbonate to form soluble salts such as copper acetate (with citric acid) and copper tartarate (with tartaric acid). The equations for the reactions are complicated and are not given. These salts are removed from the surface of the copper metal and the surface of the metal shines.

Question 14.
A man went door to door posing as a goldsmith. He promised to bring back the glitter on dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparked like new but their weight was reduced drastically. The lady got upset and after a futile argument, the man beat a hasty retreat. Can you predict the nature of the solution used by the impositer ?
Answer:
The man had actually used the solution of aqua regia (mixture of cone. HCl and cone. HNO3 in the ratio of 3 : 1 by volume) which has dissolved gold forming soluble auric chloride (AuCl3). Since gold actually reacted, there was a loss in weight of the gold bangles. With the removal of the dull layer of gold from the surface, there was original shine on the bangles. The chemical reactions have been
vedantu class 10 science Chapter 3 Metals and Non-metals 13

Question 15.
Give reason as to why copper is used to make hot water tanks and not steel (an alloy of iron).
Answer:
Copper is a better conductor of heat than steel which is an alloy of iron. Though copper is costlier than steel, it is used to make hot water tanks for storing hot water in preference to steel.

Question 16.
Differentiate between metals and non-metals on the basis of chemical properties.
For the distinction in the chemical characteristics,

Property

Metals

Non-metals

1. Nature of oxides

Oxides of the metals are generally basic in nature (Exception : ZnO and Al2O3 are amphoteric oxides). Oxides of non-metals are mostly acidic in nature (Exception : CO and N2O are neutral oxides).

2. Electrochemical behaviour

Metals normally form cations by the loss of electrons. This means that these are electropositive in nature. Non-metals normally form anions by the gain of electrons. This means that these are electronegative in nature.
3. Action with dilute acids Active metals evolve hydrogen on reacting with dilute HCl and dilute H2SO4. Non-metals do not react with dilute acids
4. Nature of compounds The compounds of metals are mostly ionic in nature. Compounds of non-metals are mostly covalent although there are many exceptions.
5. Oxidising and reducing nature Metals act as reducing agents as their atoms lose electrons. For example,
Na —— > Na+ + e
Non-metals act as oxidising agents as their atoms accept electrons. For example,
Cl + e——–>Cl

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NCERT Solutions for Class 10 Science Chapter 3 Metals and Non-metals

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

In this chapter students will learn about writing chemical equations, balancing chemical equations, different types of chemical equations, decomposition reaction, displacement reaction, double displacement reaction, oxidation and reaction, corrosion, rancidity.

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Chemistry) Chapter 1 – Chemical Reactions and Equations solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 1 – Chemical Reactions and Equations Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Solutions for Class 10 Science Chapter 1 In Text Book Questions

Question 1.
Why should magnesium ribbon be cleaned before burning in air ?
Answer:
Magnesium ribbon has generally a coating of basic magnesium carbonate on its surface. It is a mixture of magnesium hydroxide and magnesium carbonate and is slowly deposited on the surface of the metal by the action of moist air. The coating or layer prevents the metal from burning when flame is brought in contact with the metal. The surface should be properly cleaned preferably with a sand paper before burning the ribbon in air in order to remove the layer of magnesium oxide.

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Question 2.
Write the balanced equations for the following chemical reactions :
(i) Hydrogen + Chlorine ———> Hydrogen chloride
(ii) Sodium + Water ———> Sodium hydroxide + Hydrogen
(iii) Barium chloride + Aluminium sulphate ———> Barium sulphate + Aluminium chloride.
Answer:
The balanced equations are written for the symbol equations and not for word equations.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 1

Question 3.
Write the balanced equations with state symbols for the following reactions :
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and solution of sodium chloride.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride (in water) and water.
Answer:
The symbol equations in balanced form for the reactions are :
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 2

Question 4.
A solution of the substance ‘X’ is used for white washing.
(i) Name the substance ‘X’ and write its formula.
(ii) Write the reaction of the substance ‘X’ with water.
Answer:
(i) The substance lX’ is calcium oxide (also called quick lime). Its formula is CaO
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 3

Question 5.
With the help of an experiment show that in the electrolysis of acidulated water, the volume of one gas is twice the volume of the other gas. Name the gas.
Answer:
The gas is hydrogen and its volume is twice that of oxygen
tiwari academy class 10 science Chapter 1 Chemical Reactions and Equations 4

Question 6.
When you mix solutions of lead (II) nitrate and potassium iodide,
(i) What is the colour of the precipitate formed ? Name the compound involved.
(ii) Write a balanced chemical equation for the reaction
(iii) Is this a double displacement reaction ?
Answer:
(i) The precipitate is yellow in colour. The compound is lead (II) iodide with chemical formula Pbl2.
(ii) pb(NO3)(aq) + 2KI (aq) ———-> Pbl(s) + 2KNO(aq)
(iii) Yes, it is a double displacement reaction.

Question 7.
Why does the colour of copper sulphate change when an iron nail is dipped in it ?
Answer:
Iron nail acquires a brown coating of copper as a result of the displacement reaction in which iron has displaced copper from copper sulphate solution. The solution becomes light green.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 5

Question 8.
Give one example of the double displacement reaction.
Answer:
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 6

Question 9.
Identify the substances that are oxidised and the substances that are reduced in the following reactions :
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 7
Answer:
(i) In this reaction, sodium (Na) is oxidised to sodium oxide (Na2O). This means that oxygen (O2) has been reduced.
(ii) In this reaction, hydrogen (H2) is oxidised to water (H2O) while copper (II) oxide (CuO) is reduced to copper (Cu).

Question 10.
Magnesium ribbon burns with a dazzling flame in air (or oxygen) and changes to white substance magnesium oxide. Is magnesium being oxidised or reduced in this reaction ?
Answer:
The balanced chemical equation for the reaction is :
tiwari academy class 10 science Chapter 1 Chemical Reactions and Equations 8
Magnesium (Mg) is oxidised to magnesium oxide (MgO) in this reaction.

NCERT Solutions for Class 10 Science Chapter 1 NCERT End Exercises

Question 1.
WTiich of the following statements about the reaction given below are incorrect ?
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 9
(a) Lead is getting reduced
(b) Carbon dioxide is getting oxidised
(c) Carbon is getting oxidised
(d) Lead oxide is getting reduced
(i) a and b
(ii) a and c
(iii) a, b and c
(iv) all are incorrect
Answer:
(i) a and b are both incorrect
Pb is getting oxidised to PbO in backward reaction.
CO2 is getting reduced to C in backward reaction.

Question 2.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 10
The above reaction is an example of :
(a) combination reaction
(b) double displacement reaction
(c) decomposition reaction
(d) displacement reaction
Answer:
(d). It is an example of displacement reaction. The aluminium (Al) metal has displaced iron (Fe) from Fe2O3 when the reaction is carried in aqueous solution. Please note that Al lies above Fe in the reactivity series.

Question 3.
What happens when dilute hydrochloric acid is added to iron fillings ? Tick the correct answer :
(a) Hydrogen gas and iron chloride are produced
(b) Chlorine gas and iron hydroxide are produced
(c) No reaction takes place
(d) Iron salt and water are produced.
Answer:
(a). Iron chloride and hydrogen gas are produced according to the reaction
tiwari academy class 10 science Chapter 1 Chemical Reactions and Equations 11

Question 4.
What is a balanced chemical equation ? Why should chemical equations be balanced ? (CBSE 2013)
Answer:
Balanced chemical equation. A chemical equation is said to be balanced if :

  1. the atoms of different elements on both sides of the equation are equal.
  2. the equation is molecular i.e.. the gases if involved in the equation must be in the molecular form (eg., H2, O2, N2, Cl2 etc.)

Necessity to balance chemical equations. The chemical equations have to be balanced to fulfill the requirement of law of conservation of mass. According to the law,
In a chemical reaction, the mass of reactants must be the same as the mass of products and this is possible only if the atoms of different elements of the reactants and products are equal.

Question 5.
Transfer the following into chemical equations and balance them :
(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Answer:
(a) The symbol equation for the reaction is :
H2 + N2 ———> NH3
The balancing of equation is done in the following steps :
Step I: Let us count the number of atoms of all the elements of the reactants and the products on both sides of the equation.

Elements

No. of atoms of reactants 
    (L.H.S.)

No. of atoms of products
(R.H.S.)

H

2 3

N

2

1

A simple look at the equation reveals that neither the number of H nor of N atoms are equal on both sides of the equation.
Step I: In order to equate the number of H atoms on both sides, put coefficient 3 before H2 on the reactant side and coefficient 2 before NH3 on the product side.
3H2 + N2 ———–> 2NH3
Step III: On counting, the number of N atoms on both sides of the equation are also the same (2). This means that the equation is balanced.
(b) The symbol equation for the reaction is :
H2S + O2 ———–> H2O + SO2
The balancing of equation is done in the following steps :
Step I: Let us count the number of atoms of all the elements on both sides on the equation.

Elements

No. of atoms of reactants
(L.H.S.)

No. of atoms of products
(R.H.S.)

H

2 2

S

1

1

O 2

3

A simple look at the equation reveals that the number of H and S atoms are equal on both sides. At the same time, the number of O atoms are not equal.
Step II: In order to equate the number of O atoms, put coefficient 3 before O2 on the reactant side and coefficient 2 before SO2 on the product side.
H2S + 3O2 ———–> H2O + 2SO2
Step III: O atoms are still not balanced. To achieve this, put coefficient 2 before H2O on the product side.
H2S + 3O2 ————> 2H2O + 2SO2
Step IV: To balance S atoms, put coefficient 2 before H2S on the reactant side.
2H2S + 3O2 ————> 2H2O + 2SO2
On inspection, the number of atoms of all the elements in both sides of the equation are equal. Therefore, the equation is balanced.
(c) The symbol equation for the reaction is :
BaCl2 + Al2(SO4)3 ———-> A1Cl3 + BaSO4
The balancing of equation is done in the following steps :
Step I: Let us count the number of atoms of all the elements on both sides of the equation.

Elements

No. of atoms of reactants (L.H.S.)

No. of atoms of products (R.H.S.)

Ba

1 1

A1

2 1

Cl

2

3

S 3

1

O 12

4

A simple look at the equation reveals that only Ba atoms are equal on both sides. The rest of the atoms are to be balanced. It is done as follows :
Step II: In order to equate the number of Al atoms, put coefficient 2 before AlCl3 on the product side.
BaCl2 + Al2(SO4)3 ———-> 2AICl3 + BaSO4
Step III: In order to balance Cl atoms, put coefficient 3 before BaCl2 on the reactant side.
3BaCl2 + Al2(SO4)3 ———–> 2AlCl3 + BaSO4
Step IV: To balance Ba atoms, put coefficient 3 before BaSO4 on the product side.
3BaCl2 + Al2(SIO4)3 ———-> 2AlCl3 + 3BaSO4
Step V: On inspection, the number of S and O atoms on both sides of the equation are also found to be equal. Thus, the equation is in balanced form.
(d) The symbol equation for the reaction is :
K + H2O ———–> KOH + H2
The balancing of the equation is done in the following steps :
Step I. Let us count the number of atoms of all the elements on both sides.

Elements

No. of atoms of reactants (L.H.S.)

No. of atoms of products (R.H.S.)

K

1 1

H

2 3

O

1

1

A simple look at the equation reveals that the number of K and O atoms on both sides of the equation are equal. At the same time, the number of H atoms are not equal.
Step II: To balance the number of H atoms, put coefficient 2 before KOH on the product side and 2 before H2O on the reactant side.
K + 2H2O ———> 2KOH + H2
Step III: To balance the number of K atoms in the above equation, put coefficient 2 before K atom on the reactant side.
2K + 2H2O ———> 2KOH + H2
Step IV: On inspection, the number of atoms of all the elements are found to be equal on both sides of the equation. It is balanced.

Question 6.
Balance the following chemical equations :
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 12
Answer:
(a) The symbol equation as given for the reaction is :
HNO3 + Ca(OH)2 ——–> Ca(NO3)2 + H2O
The balancing of the equation is done in the following steps :
Step I: Let us count the number of atoms of all the elements on both sides of the equation.

Elements

No. of atoms of reactants (L.H.S.)

No. of atoms of products (Products)

H

3 2

O

5 7
N 1

2

Ca 1

1

A simple look at the equation reveals that the number of Ca atoms are equal on both sides.
Step II: In order to equate the number of N atoms, put coefficient 2 before HNO3 on the reactant side.
2HNO3 + Ca(OH)2 ———-> Ca(NO3)2 + H2O
Step III: In order to equate the number of H atoms, put coefficient 2 before H2O on the product side.
2HNO3 + Ca(OH)2 ———-> Ca(NO3)2 + 2H2O
Step IV: On inspection the number of O atoms on both sides of the equation is the same i.e., 8. Therefore, the equation is balanced.
(b) The symbol equation as given for the reaction is :
NaOH + H2SO4 ———-> Na2SO4 + H2O
Step I: Let us count the number of atoms of all the elements on both sides of the equation.

Elements

No. of atoms of reactants (L.H.S.)

No. of atoms of products (R.H.S.)

H

3 2

O

5 5
Na 1

2

S 1

1

A simple look at the equation reveals that the number of O and S atoms are equal on both sides.
Step II: In order to equate the number of Na atoms, put coefficient 2 before NaOH on the reactant side.
2NaOH + H2SO4 ———-> Na2SO4 + H2O
Step III: In order to equate the number of H atoms, put coefficient 2 before H2O on the product side.
2NaOH + H2SO4 ———> Na2SO4 + 2H2O
Step IV: On inspection, the number of O atoms on both sides of the equation is the same i.e., 6. Therefore, the equation is balanced.
(c) The symbol equation as given for the reaction is already balanced.
NaCl + AgNO3 ———-> AgCl + NaNO3
On inspection, the number of atoms of all the elements are found to be equal on both sides of the equation. It is in the balanced form.
(d) The symbol equation as given for the reaction is :
BaCl2 + H2SO4 ———-> BaSO4 + HCl
Step I: Let us count the number of atoms of all the elements on both sides of the equation.

Elements

No. of atoms of reactants (L.H.S.)

No. of atoms of products (R.H.S.)

Ba

1 1

H

2 1

O

4 4

S

1

1

Cl 2

1

A simple look at the equation reveals that the number of Ba, S and O atoms are equal on both sides.
Step II: In order to equate the number of Cl atoms, put coefficient 2 before HCl on the product side.
BaCl2 + H2SO4 ———> BaSO4 + 2HCl
Step III: On inspection, the number of H atoms on both sides of the equation is the same i. e., 2. Therefore, the equation is balanced.

Question 7.
Write the balanced equations for the following reactions :
(a) Calcium hydroxide + Carbon dioxide ———-> Calcium carbonate + Water
(b) Lead + Copper chloride ———-> Lead chloride + Copper
(c) Barium chloride + Sodium sulphate ———-> Barium sulphate + Sodium chloride
(d) Zinc + Silver nitrate ———–> Zinc nitrate + Silver.
Answer:
All these equations are in word form whereas the balanced equations are written in symbol form.
(a) Ca(OH)2 + CO2 ———-> CaCO3 + H2O
(b) Pb + CuCl2 ———-> PbCl2 + Cu
(c) BaCl2 + Na2SO4 ———> BaSO4 + 2NaCl
(d) Zn + 2AgNO3 ———–> Zn(NO3)2 + 2Ag

Question 8.
Write the balanced chemical equations for the following reactions and identify the type of reaction :
(a) Potassium brormide (aq) + Barium iodide (aq) ————> Potassium iodide(aq) + Barium bromide (aq)
(b) Zinc carbonate (aq) ————> Zinc oxide (aq) + Carbon dioxide (aq)
(c) Hydrogen (aq) + Chlorine (aq) ———> Hydrogen chloride (aq)
(d) Magnesium (aq) + Hydrochloric acid (aq) ———–> Magnesium chloride (aq) + Hydrogen(aq).
Answer:
(a)          2KBr (aq) + BaI(aq) ——–> 2Kl (aq) + BaBr2 (aq)
The reaction is known as double displacement reaction.
(b)          ZnCO3(s) ———-> ZnO(s) + CO2(g)
The reaction is known as decomposition reaction. ‘
(c)          H2(g) + Cl2(g) ———–> 2HCl (g)
The reaction is known as combination reaction.
(d)          Mg (aq) + 2HCl (aq) ———–> MgCl(aq) + H2(g)
The reaction is known as displacement reaction.

Question 9.
What do you mean by exothermic and endothermic reactions ? Give examples.
Answer:
A chemical reaction is said to be exothermic in which a certain amount of heat energy is released. The container in which reaction is carried gets heated up. For example,
N(g) + 3H2(g) ———> 2NH3 (g) + 92 kj
CH4(g) + 2O2(g) ———> CO(g) + 2H2O (l) + 890 kj
NaOH (aq) + HCl (aq) ———> NaCl (aq)+ H2O (aq) + 57.5 kj
A chemical reaction is said to be endothermic in which a certain amount of heat energy is absorbed. The container in which the reaction is carried becomes cold. For example,
N2(g) + O(g) ———-> 2NO (g) – 180 kj
C(s) + H2O (aq) ———-> CO (g) + H2(g) – 130 kj

Question 10.
Why is respiration considered an exothermic reaction ? (CBSE 2011)
Answer:
Respiration is the most important biochemical reaction which releases energy in the cells. When we breathe in air, oxygen enters our lungs. It binds itself to haemoglobin present in red cells and is carried to millions of cells present on the body. Respiration occurs in these cells and is accompanied by the combustion of glucose producing carbon dioxide water and heat energy.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 13

Question 11.
Why are decomposition reactions called opposite of combination reactions ? Write equations for these reactions.
Answer:
Combination reaction may be defined as the reaction in which two or more substances combine under suitable conditions to form a new substance. For example,
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 14
A decomposition reaction may be defined as the reaction in which a single substance decomposes or splits into two or more substances under suitable conditions.
For example,
tiwari academy class 10 science Chapter 1 Chemical Reactions and Equations 15
It may be concluded that a certain substance is formed or synthesised in combination reaction and it breaks or splits in decomposition reaction. Therefore, the two reactions oppose each other.

Question 12.
Write equations for each decomposition reaction, where energy is supplied in the form of heat, light and electricity.
Answer:
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 16

Question 13.
What is the difference between displacement and double displacement reactions ? Write equations for these reactions. (CBSE 2011)
Answer:
In a displacement reaction, one element takes the place of another in a compound dissolved in a solution. For example,
Fe(s) + CuSO4 (aq) ———> FeSO4 (aq) + Cu(s)
In a double displacement reaction, one component each of both the reacting molecules get exchanged to form the products. For example,
HCl (aq) + NaOH(aq) ———> NaCl (aq) + H2O (aq)

Question 14.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write chemical equation involved.
Answer:
The chemical equation for the displacement reaction is :
Cu(s) + 2AgNO(aq) ———-> Cu(NO3)2 (aq) + 2Ag (s).

Question 15.
What do you mean by precipitation reaction ? Explain giving examples.
Answer:
In a precipitation reaction, one of the products formed during the reaction does not dissolve in solution and gets settled at the surface of the container (beaker or tube). It is known as a precipitate. For example,
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 17

Question 16.
Explain the following in terms of gain or loss of oxygen with two examples of each,
(a) oxidation
(b) reduction.
Answer:
(a) Oxidation involves the gain of oxygen by a substance in a chemical reaction. For example,
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 18
(b) Reduction involves the loss of oxygen from a substance in a chemical reaction. For example,
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 19

Question 17.
A shining brown coloured element ‘X’ on heating in’ air becomes black in colour. Name the element ‘X’ and the black coloured compound formed. (CBSE 2013)
Answer:
The element ‘X’ is copper and the black coloured compound is copper (II) oxide also known as cupric oxide.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 20

Question 18.
Why do you apply paint on iron articles ?
Answer:
Paint forms a protective coating on the surface of iron. Both oxygen and moisture (present in air) cannot have a direct contact with the surface of the iron metal. Therefore, the surface gets protected against rusting.

Question 19.
Oil and fat containing food items are flushed with nitrogen. Why ?
Answer:
Oil and fat containing food items or etables get rancid due to oxidation by air or oxygen. In case the container or bag is flushed with nitrogen, then oxidation or rancidity will be checked.

Question 20.
Explain the following terms wih one example of each.
(a) Corrosion
(b) Rusting.
Answer:
Corrosion may be defined as the chemical process of slow eating up of the surfaces of certain metals when kept in open for a long time.
Quite often, when we open the bonet of a car after a long time, we find a deposit around the terminals of the battery. This is because of corrosion of the terminals. Black coating on the surface of silver and green layer on the surface of copper are the examples of corrosion. In case of iron, corrosion is called rusting. Rust is a chemical substance which is soft and also porous. It is brown in colour and is formed by the chemical action of moist air (containing CO2 and H2O) on iron. It is basically an oxidation reaction and formula of rust is Fe2O3.xH2O. It is very slow in nature and once started keeps on.
NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations 21
Both corrosion and rusting are very harmful and cause damage to the buildings, railway tracks, automobiles and other objects/materials where metals are used. We quite often hear that an old building has collapsed of its own causing loss of both lives and property. This is on account of the rusting of iron which is used in making the structures particularly the roof. Corrosion also causes constant damage to the statues made up of marble which is chemically calcium carbonate (CaCO3). Both sulphuric acid and nitric acid present in the rain water dissolve calcium carbonate to form calcium sulphate and calcium nitrate respectively.
CaCO3 + H2SO———— > CaSO4 + CO2 + H2O

CaCO3 + 2HNO3 ———— > Ca(NO3)2 + CO2 + H2O

In addition to this, traces of hydrogen sulphide gas (H2S) present in atmosphere form black stains on these statues due to calcium sulphide which is black in colour.
CaCO3 + H2S  ———–> CaS + H2O + CO2
Corrosion has caused huge damage to our historical monuments including ‘Taj Mahal’ which is regarded as the eighth wonder. Marble is chemically CaCO3. Polluted air contains both H2SO4 and HNO3 along with traces of H2S gas. They react chemically with CaCO3 as shown above. As a result, this historical monument which is the pride of India is being constancy corroded. Every effort must be made to protect ‘Taj Mahal’ and other similar monuments which are our treasure. Corrosion (or rusting) occurs in metals only. We shall study it detail and the measures to check corrosion in chapter 3 on Metals and Non-Metals.

NCERT Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

Hope given NCERT Solutions for Class 10 Science Chapter 1 are helpful to complete your science homework.

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NCERT Solutions for Class 10 Science Chapter 15 Our Environment

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

These Solutions are part of NCERT Solutions for Class 10 Science. Here we have given NCERT Solutions for Class 10 Science Chapter 15 Our Environment. LearnInsta.com provides you the Free PDF download of NCERT Solutions for Class 10 Science (Biology) Chapter 15 – Our Environment solved by Expert Teachers as per NCERT (CBSE) Book guidelines. All Chapter 15 – Our Environment Exercise Questions with Solutions to help you to revise complete Syllabus and Score More marks.

NCERT Questions

In Text Questions

Question 1.
Why are some substances biodegradable and some non-biodegradable ? (CCE 2011)
Answer:
Biodegradable substances are substances of organic origin which can be broken down by enzymes of saprophytes, e.g., garbage, sewage, livestock waste, agriculture waste. Non-biodegradable substances are man-made substances which cannot be degraded by saprophytes because they lack the enzymes to do so e.g., waste plastic and polythene articles.

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Question 2..
Give any two ways in which biodegradable substances would affect the environment.
(CBSE Delhi 2007, AI 2009 C)
Answer:

  1. Stink: Within a day or so waste biodegradable substances begin to stink and produce foul gases.
  2. Pests and Pathogens: The decaying biodegradable substances become breeding places of flies and many other pests. They also contain a number of pathogens. Flies and other pests carry the germs to all the places visited by them resulting in spread of diseases.

Question 3.
Give any two ways in which non-biodegradable substances would affect the environment. (CBSE AI 2009 C)
Answer:

  1. Dumping Area: Dumping of non-biodegradable substances on a piece of land converts the same into barren land. It is also called landscape pollution.
  2. Biological Magnification: Pesticides, heavy metals and other chemicals enter water and food chains. They accumulate in toxic proportions and harm all kinds of living organisms. Their concentration also increases with rise in trophic level. Human beings are harmed the most because man lies at the top of every food chain.

Question 4.
What are trophic levels ? Give an example of a food chain and state the trophic levels in it.
Answer:
(a) Trophic Levels. They are steps or divisions of food chain which are characterised by particular methods of obtaining food, e.g., producers (T1), herbivores (T2), primary carnivores (T3), etc.
NCERT Solutions for Class 10 Science Chapter 15 Our Environment 5
(b) Flow of Energy Through Food Chain. Energy enters a food chain through producers. Producers or green plants trap solar energy and convert it into chemical energy of food during photosynthesis. From producers energy passes into herbivores. A lot of energy dissipates during transfer and utilization of food energy by herbivores (10% law). From herbivores the food energy passes into primary carnivores, again with a lot of dissipation. Only about 10% of herbivore energy is passed into body mass of primary carnivores. From primary carnivores, nearly 10% energy passes into secondary carnivores and so on. It is ultimately lost as heat.

Question 5.
What is the role of decomposers in the ecosystem ?
Answer:
Ecosystem is a self-contained ecological system which consists of a distinct biotic community and the physical environment, both interacting and exchanging materials between them. It is a structural and functional unit of biosphere. Ecosystem is an open system which requires a regular input of energy and circulation of matter for its sustenance. Different ecosystems are in contact with one another. Though they are distinct, but exchange of materials can occur amongst them. Ecosystem can be small (e.g., rotting piece of wood) or large (e.g., forest, ocean), temporary (e.g., rain fed pond) or permanent (e.g., lake, forest), natural or artificial.
Natural Ecosystems: They are ecosystems which develop in nature without human support. Natural ecosystems are of two types, terrestrial and aquatic. Terrestrial ecosystems occur over land. They are of three major types -— desert, grassland and forest. Aquatic ecosystems are found in water bodies, e.g., ponds, lakes, rivers (fresh water), estuaries, marine (salt water).
Artificial Ecosystems: They are ecosystems which have been p/g. 5.7. An aquarium. created and are maintained by human beings. Artificial ecosystems are also called man-made or anthropogenic ecosystems. Agroecosystem is the largest man-made ecosystem. Garden is a common artificial ecosystem maintained by most institutes. It has various types of plants grown and maintained by gardener — grass, trees, flower bearing plants like Rose, Jasmine, Sunflower. A number of animals become residents and visitors of the garden. Aquarium is another artificial ecosystem.

Question 6.
What is ozone and how does it affect any ecosystem ?
Answer:
Definition of Ozone: Ozone is a triatomic molecule made up of three atoms of oxygen, O3.
Effect:

  1. Protection against ultraVoilet rays if present in stratosphere,
  2. Ozone dissipates the energy of ultraviolet rays by undergoing dissociation following by reassociation
    NCERT Solutions for Class 10 Science Chapter 15 Our Environment 1

If present in the atmosphere of ecosystem, it is highly toxic causing injury to mucous membranes, eye irritation and internal haemorrhages in animals and humans. It harms plants by destroying photosynthetic cells producing necrosis.

Question 7.
How can you help in reducing the problem of waste disposal ? Give any tivo methods.
Answer:
Waste disposal is becoming the biggest problem of all local bodies. It is consuming a big chunk of their revenues. Even then the points of collection are turning into stinking areas. Transport of waste to disposal site is seldom perfect. There is stink all the way. A lot of waste is thrown on the roads by the vehicles carrying the waste.
The quantity of waste can be reduced if you form the habit of separation of waste into biodegradable and non-biodegradable parts.

  1. Non-biodegradable Waste. Most often the non-biodegradable waste is recycled. It is taken away by rag pickers.
  2. Biodegradable Waste. Biodegradable waste is putressible. It can be composted or vermicomposted to prepare compost for your kitchen gardens. The technique can also be used in schools and other institutions. Some institutes in big cities have installed incinerators for disposal of combustible components of waste. Hospital waste is being compulsorily incinerated to reduce contamination and spread of diseases.

NCERT Chapter End Exercises

Question 1.
Which of the following groups contains only easily biodegradable items ?
(A) Grass, flower and leather
(B) Grass, wood and plastic
(C) Fruit peels, cake and lime juice ,
(D) Cake, wood and grass.
Answer:
(A), (C), (D).

Question 2.
Which of the following constitute a food chain
(A) Grass, wheat and mango
(B) Grass, goat and human
(C) Goat, cow and elephant
(D) Grass, fish and goat.
Answer:
(B).

Question 3.
Which of the following are environment friendly practices ?
(A) Carrying cloth bags to put purchases in while shopping
(B) Switching off unnecessary lights and fans
(C) Walking to school instead of getting your mother to drop you on her scooter
(D) All the above.
Answer:
(D).

Question 4.
What will happen if you kill all the orgainsms in one trophic level ?
Answer:
Higher Trophic Level. All the organisms will be starved and die. Lower Trophic Level. The organisms will increase in number much beyond the carrying capacity of the enviroment. They will become weak and fall easy prey to various diseases, ultimately resulting in decline in population. The ecosystem may get converted into a desert.

Question 5.

  1. Will the impact of removing all the organisms in a trophic level be different for different trophic levels ?
  2. Can the organisms of any trophic level be removed without causing any damage to the ecosystem ?

Answer:

  1. Yes. Impact of removing all the organisms of a trophic level depends upon the trophic level. Removal of producers will kill all the consumers. Killing of carnivores will increase the number of herbivores which in turn will eat up all the producers. They would themselves die of starvation. However, if herbivores are removed, all the carnivores of the area will die. The plants which are dependent upon animals for pollination will fail to reproduce and die ultimately. Others would persist and increase in number, again much beyond the carrying capacity of the environment.
  2. No. Removal of all the organisms of a trophic level will disturb the ecosystem – killing of higher trophic level organisms and explosion in populations of lower level organisms. Higher number of lower trophic level organisms will adversely affect the ecosystem by consuming whole or major part of their prey.

Question 6.
What is biological magnification ? Will the levels of this magnification be different at different levels of the ecosystem ?
Answer:
Definition: Biological magnification is increase in the concentration of a chemical per unit weight of the organisms with the successive rise in trophic level. In one study it was found that concentration of harmful chemical like DDT will increase 80,000 times the concentration present in water.
Levels of Magnification at Different Levels of Ecosystem. Levels of biomagnification of a chemical will be different at different levels of ecosystem. In one study it was found that concentration of a pesticide was 0.002 ppm in water, 0.05 ppm in plankton, 2.4 ppm in fish and 16.0 ppm in fish eating bird.
vedantu class 10 science Chapter 15 Our Environment 2

Question 7.
What are the problems caused by the nonbiodegradable waste we generate ?
Answer:

  1. Volume: Being non-biodegradable, the volume of these wastes will not decrease by natural process of decomposition.
  2. Land Use: They have to be dumped over land. The land becomes unfit for any other purpose.
  3. Heavy Metals: Heavy metals present in industrial wastes (e.g., copper, lead, chromium, nickel, mercury) remain in the soil indefinitely. Slowly they pass into vegetation and crops harming both humans and animals.
  4. Pesticides and Other Toxins: They pollute underground water, surface water and soil. The chemicals enter food chain and become concentrated, harming animals and humans.
  5. Rag Pickers: In the process of removing recyclable materials from solid wastes, the rag pickers are exposed to many diseases and toxins.
  6. Recycling: Recycling of materials produces only’inferior quality products. Recycling of polythene and plastic is accompanied by release of carcinogenic toxins like dioxins and furans.

Question 8.
If all the waste we generate is biodegradable, will this have no impact on the environment ?
Answer:
The impact on the environment will depend upon the system of collecting, transporting and disposal of biodegradable waste. If it is regular and clean, the impact will be little in urban areas. Only some effect will be observed at disposable site which will emit foul gases and expose the sanitary workers to contamination. The same can also be reduced by increased use of machines and wearing of protective gear by the sanitary workers.

Question 9.
Why is damage to the ozone layer a cause of concern What steps are being taken to limit this damage ?
Answer:
Cause of Concern: Ozone layer present in the stratosphere has thinned out by about 8% over the equator and more so over the antarctica where a big ozone hole appears every year.
This has increased the level of UV-B radiations reaching the earth by 15-20%. These radiations are causing increased number of skin cancers, cataracts and reduced immunity in human beings. There is increased incidence of blinding of animals, death of young ones, reduced photosynthesis, higher number of mutations and damage to articles.
Steps to Limit Damage:

  1. Ban on production and use of halons.
  2. Ban on production and use of chlorofluorocarbons.

Selection Type Questions

Alternate Response Type Questions
(True/False, Right(√)/Wrong (x), Yes/No)

Question 1.
Wastes are of two types, biodegradable and non-biodegradable.
Question 2.
Non-biodegradable articles are the ones which cannot be digested.
Question 3.
Ozone is formed in stratosphere by action of ultravoilet radiations on oxygen.
Question 4.
Earth is kept warm due to green house flux.
Question 5.
Rag pickers remove reusable articles.
Question 6.
Pyrolysis is aerobic combustion while incineration is anaerobic combustion.
Question 7.
Biodegradable wastes should be separated and kept in blue colour bins for garbage collectors.
Question 8.
Food web ensures survival of all types of trophic levels.

Matching Type Questions

Question 9.
Match the articles in columns I and II (single matching) :

Column I

Column II

(a) Hawk (i) Producer
(b) Hare (ii) Top carnivore
(c) Grass (iii) Green house gas
(d) Carbon dioxide (iv) Herbivore

Question 10.
Match the contents of columns I, II and III (double matching)

Column I

Column II

Column III

(a)    Ecosystem

(b)    Producers

(c)    Omnivores

(d)    Persistent pesticide

(i) Food chain

(ii) Abiotic components

(iii) Transducer

(iv) Plant food

p.  Food energy

q.  Biomagnification

r. Animal food

s. Biotic components

Question 11.
To what trophic level (T1, T2, T3, T4) do the following belong (key or check list items)
NCERT Solutions for Class 10 Science Chapter 15 Our Environment 3

Question 12.
Match each stimulus with appropriate response :

Activity

Deforestation (A) Increase runoflf (B)

Destruction of wild life (C)

(i) Hunting

(ii) Felling of trees

(iii) Litter Collection

Fill In the Blanks

Question 13. Waste substances that are broken down by microbes are called ………. : ………… .
Question 14. Gardens and crop fields are ………………. ecosystems.
Question 15. Microorganisms are called ……………… as they break down the complex organic remains into simple inorganic substances.
Question 16. Decrease in ozone in stratosphere is linked to release of synthetic chemicals like ……………… .
Question 17. Improvement in life style often results in increased generation of …………. : ………… material.

Answers:
vedantu class 10 science Chapter 15 Our Environment 4

NCERT Solutions for Class 10 Science Chapter 15 Our Environment

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