Question

Calculate the number of molecules in (i) 16 g of sulphur (ii) 1.5 moles of ammonia

Answer 1

ammonia=NH4
molecular mass=
$7 \times 2 + 1 \times 4 \\ 1 4+ 4 \\ = 18$
given no of moles=1.5moles
no of molecules=
$n0 \times no \: of \: moles \\ 6.022 \times 10 {}^{23} \times 1.5 \\ = 9.033 \times 10 {}^{23}$
in sulphur,
given mass=16g
atomic mass=32g
therefore,no of moles,
$= 32 \div 16 \\ = 2moles$
therefore,no of particles=
$= 6.022 \times 10 {}^{23} \times 2 \\ = 12.044 \times 10 {}^{23particles}$