Question

The molecular formula for elemental sulphur is $S_8$. 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) No. of moles in 256 g $S_8$ = 1 mole
So, no. of moles in 5.12 g = $\frac{5.12}{256}$ = 0.02 moles

(b) No. of molecules $=0.02\times 6.023\times {10}^{23}=1.2\times {10}^{22}$ molecules
No. of atoms in 1 molecule of S = 8
So, no. of atoms in $1.2\times {10}^{22}$​​​​​​​ molecules $=1.2\times {10}^{22}\times 8=9.635\times {10}^{22}$ molecules