On analysis, a substance was found to have the following percentage composition:
K = 31.84, Cl= 28.98 and O = 39.18
Calculate its molecular formula if its molecular mass is 122.5.
Solution:
Step 1: Arriving at the empirical formula in four steps mentioned as-

The empirical formula of the compound is KClO3.
Step 2- Calculation of empirical formula mass
The next step is to calculate the empirical formula mass,
Empirical formula mass of KClO3 = 39 + 35.5 + 3 x 16 = 122.5
Step 3- Finding the value of n
The value of n is obtained by dividing the empirical formula mass by the molecular mass of the sample.

= 122.5/122.5 = 1
This means that the empirical is same as the molecular formula, that is, KClO3.
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