Question

A compound has 8% magnesium by mass. Calculate it's minimum molecular mass.

Answer 1

Answer:

The compound has sulphur=8%

∴ 8 g of S is present in 100 g.

[Least molecular mass means that at least one atom of sulphur should be present in a molecule.]

∴ 32 g of S is present in

8

100

×32=400 g

Answer 2

Answer:

There is a quick shortcut for it

8% * M = 24

M = 2400/8 = 300 g

We can apply this shortcut to every question which asks min. molecular weight .

% * M = Mass of element given

I hope it helps .