Question

The molecular formula for eelemental sulphur si $S_8$. In a sample of 5.12 g of slphur:
(a) how many moles of sulphur are present ?
(b) HOw many molecules and atoms are present?

Answer 1

(a) molecular mass = 32 $\times$ 8 = 256 g
moles = $\frac{givenmass}{molecularmass}$ = $\frac{5.12}{256}$ = 0.02

(b) molecules = moles $\times$ $6.02\times {10}^{23}$ = 0.02 $\times$ $6.02\times {10}^{23}$ = 0.1204 $\times {10}^{23}$
Atoms in 1 molecule = 8
Total number of atoms = 0.1204 $\times {10}^{23}\times 8$ = 0.9632 $\times {10}^{23}$