• Skip to main content
  • Skip to secondary menu
  • Skip to primary sidebar
  • Skip to footer
  • NCERT Solutions
    • NCERT Books
  • Class 10
  • Class 9
  • Class 8
  • Class 7
  • Class 6
  • Class 11
  • Class 12
  • MCQ Questions
    • CBSE MCQ

Learn Insta

RD Sharma Solutions , RS Aggarwal Solutions and NCERT Solutions

  • Extra Questions
  • CBSE Notes
  • RD Sharma Solutions
    • RD Sharma Class 12 Solutions
    • RD Sharma Class 11 Solutions
    • RD Sharma Class 10 Solutions
    • RD Sharma Class 9 Solutions
    • RD Sharma Class 8 Solutions
  • RS Aggarwal Solutions
    • RS Aggarwal Solutions Class 10
    • RS Aggarwal Solutions Class 9
    • RS Aggarwal Solutions Class 8
    • RS Aggarwal Solutions Class 7
    • RS Aggarwal Solutions Class 6
  • ML Aggarwal Solutions
    • ML Aggarwal Class 10 Solutions
    • ML Aggarwal Class 9 Solutions
    • ML Aggarwal Class 8 Solutions
    • ML Aggarwal Class 7 Solutions
    • ML Aggarwal Class 6 Solutions
  • English Grammar
    • Words with Letters
    • English Summaries
    • Unseen Passages

Empirical Formula and Molecular Formula

July 29, 2021 by Prasanna

Find free online Chemistry Topics covering a broad range of concepts from research institutes around the world.

Empirical Formula and Molecular Formula

Elemental analysis of a compound gives the mass percentage of atoms present in the compound. Using the mass percentage, we can determine the empirical formula of the compound. Molecular formula of the compound can be arrived at from the empirical formula using the molar mass of the compound.

Empirical formula of a compound is the formula written with the simplest ratio of the number of different atoms present in one molecule of the compound as subscript to the atomic symbol. Molecular formula of a compound is the formula written with the actual number of different atoms present in one molecule as a subscript to the atomic symbol.

Let us understand the empirical formula by considering acetic acid as an example.

The molecular formula of acetic acid is C2H4O2

The ratio of C : H : O is 1 : 2 : 1 and hence the empirical formula is CH2O.

Determination of Empirical Formula from Elemental Analysis Data:

Step 1:

Since the composition is expressed in percentage, we can consider the total mass of the compound as 100 g and the percentage values of individual elements as mass in grams.

Step 2:

Divide the mass of each element by its atomic mass. This gives the relative number of moles of various elements in the compound.

Step 3:

Divide the value of relative number of moles obtained in the step 2 by the smallest number of them to get the simplest ratio.

Step 4:

(only if necessary) in case the simplest ratios obtained in the step 3 are not whole numbers then they may be converted into whole number by multiplying by a suitable smallest number.

Example:

1. An acid found in Tamarind on analysis shows the following percentage composition: 32 % Carbon; 4 % Hydrogen; 64 % Oxygen. Find the empirical formula of the compound.

Empirical Formula and Molecular Formula img 1

The empirical formula is C2H3O3

2. An organic compound present in vinegar has 40 % carbon, 6.6 % hydrogen and 53.4 % oxygen. Find the empirical formula of the compound.

Empirical Formula and Molecular Formula img 2

The empirical formula is CH2O

Molecular formula of a compound is a whole number multiple of the empirical formula. The whole number can be calculated from the molar mass of the compound using the following expression

Empirical Formula and Molecular Formula img 3

Calculation of Molecular Formula from Empirical Formula:

Empirical Formula and Molecular Formula img 4

Let us understand the calculations of molecular formula from the following example.

Two organic compounds, one present in vinegar (molar mass: 60 g mol-1), another one present in sour milk (molar mass: 90 g mol-1) have the following mass percentage composition. C-40%, H-6.6%; O-53.4%. Find their molecular formula.

Since both compounds have same mass percentage composition, their empirical formula are the same as worked out in the example problem no 2. Empirical formula is CH2O. Calculated empirical formula mass (CH2O) = 12 + (2×1) + 16 = 30 g mol-1.

Formula for the compound present in vinegar

Empirical Formula and Molecular Formula img 5

∴ Molecular formula = (CH2O)2
= C2H4O2 (acitic acid)

Caluculation of molecular formula for the compound present in sour milk.

Empirical Formula and Molecular Formula img 6

Molecular formula = (CH2O)3
= C3H6O3 (lactic acid)

Filed Under: Chemistry

Primary Sidebar

  • Maths NCERT Solutions
  • Science NCERT Solutions
  • Social Science NCERT Solutions
  • English NCERT Solutions
  • Hindi NCERT Solutions
  • Physics NCERT Solutions
  • Chemistry NCERT Solutions
  • Biology NCERT Solutions
RS Aggarwal Solutions RD Sharma Solutions
RS Aggarwal Class 10 RD Sharma Class 10
RS Aggarwal Class 9 RD Sharma Class 9
RS Aggarwal Class 8 RD Sharma Class 8
RS Aggarwal Class 7 RD Sharma Class 11
RS Aggarwal Class 6 RD Sharma Class 12

Recent Posts

  • Mechanical Properties of Solids Class 11 Important Extra Questions Physics Chapter 9
  • Selina Concise Mathematics Class 10 ICSE Solutions Chapter 8 Remainder and Factor Theorems Ex 8A
  • MCQ Questions for Class 9 Maths Chapter 2 Polynomials with Answers
  • MCQ Questions for Class 7 Maths Chapter 2 Fractions and Decimals with Answers
  • English Grammar for Class 6, 7, 8, 9, 10, 11 and 12
  • Unscramble Words With Letters | Make Words with These Letters
  • Fractions and Decimals Class 7 Notes Maths Chapter 2
  • MCQ Questions for Class 6 Maths Chapter 8 Decimals with Answers
  • MCQ Questions for Class 6 Maths Chapter 1 Knowing Our Numbers with Answers
  • RD Sharma Class 10 Solutions Chapter 12 Heights and Distances Ex 12.1
DMCA.com Protection Status

Footer

CBSE Library
NCERT Library
NCERT Solutions for Class 12
NCERT Solutions for Class 11
NCERT Solutions for Class 10
NCERT Solutions for Class 9
NCERT Solutions for Class 8
NCERT Solutions for Class 7
NCERT Solutions for Class 6
ML Aggarwal Class 10 ICSE Solutions
Concise Mathematics Class 10 ICSE Solutions
CBSE Sample Papers
cbse
ncert
English Summaries
English Grammar
Biology Topics
Microbiology Topics
Chemistry Topics
Like us on Facebook Follow us on Twitter
Watch Youtube Videos Follow us on Google Plus
Follow us on Pinterest Follow us on Tumblr
Percentage Calculator

Copyright © 2022 Learn Insta