Question

A compound contains 40% by mass of oxygen . What would be the minimum molecular mass ? [2]

Answer 1

The compound has sulphur = 40%
For minimum molecular weight at least one oxygen atom should be present in the compound, One atom means 16 g of oxygen
Suppose total weight of compound is 100g.
∴ 40 g of O is present in 100g
∴ 16 g of O is present in (100/40)*16 = 40gm Ans
(If you take the grams equal to molecular mass of element, you will get answer in molecular weight, here we took weight of oxygen = its molecular mass 16, so the total weight 40 that we got is the molecular mass of compound )