Question

if an oxide of carbon is 20% by mass what is its empirical formula

Answer 1

Let's assume that the compound has a mass of 100g.

Moles of Carbon =$\frac{80g}{12g/mol}=6.66mol$

Moles of Oxygen =$\frac{20}{16g/mol}=1.25mol$

$C:\frac{6.66}{6.66}=1$

$O:\frac{1.25} {6.66}=0$

Thus the imperial formula $=CO$