# Solve the following problem: A substance, on analysis, gave the following percent composition: Na = 43.4%, C = 11.3% and O = 45.3%. Calculate the empirical formula. (At. mass Na = 23 u, C = 12 u, - Chemistry

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Solve the following problem:

A substance, on analysis, gave the following percent composition: Na = 43.4%, C = 11.3% and O = 45.3%. Calculate the empirical formula. (At. mass Na = 23 u, C = 12 u, O = 16 u).

#### Solution

Given: Atomic mass of Na = 23 u, C = 12 u, and O = 16 u
Percentage of Na, C and O = 43.4%, 11.3% and 45.3% respectively.

To find: The empirical formula of the compound

Calculation:

Moles of Na = "% of Na"/"Atomic mass of Na"=43.4/ 23 = 1.89 mol

Moles of C = "% of C"/"Atomic mass of C"=11.3/12 = 0.94 mol

Moles of O = "% of O"/"Atomic mass of O"=45.3/16 = 2.83 mol

Hence, the ratio of number of moles of Na : C : O is

1.89/0.94 = 2, 0.94/0.94 = 1 and 2.83/0.94 = 3

Hence, empirical formula is Na2CO3.

Empirical formula of the compound = Na2CO3

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#### APPEARS IN

Balbharati Chemistry 11th Standard Maharashtra State Board
Chapter 2 Introduction to Analytical Chemistry
Exercises | Q 4. (H) | Page 24