Question

Convert into the mole a) 12gof O2 gas

Answer 1

32g of O_{2} = 1 mol
1g of O_{2} = \frac{1}{32} mol
12f of O_{2} = \frac{12}{32} mol = 0.375 mol

Answer 2

ok...
what is the formula to find the no. of moles..???
It is:- given mass÷atomic mass or molecular mass

so......
the given mass in the question is 12g
and the molecular mass of di-oxygen is 32
(because O2 contains two atoms of oxygen so 16+16=32)

so... According to the formula

12÷32=0.375 moles