Question

Find how many moles of atoms are there in:
i) $2g$ of nitrogen. ii) $23g$ of sodium iii) $40g$ of calcium. iv) $1.4$ of lithium v) $32g$ of sulphur

Answer 1

(i) Nitrogen exists as diatomic molecule $N_2$

$\therefore$ Moles of atoms of $N=2\times$ moles of $N_2$

$=2\times \frac{2}{14\times 2}=0.142$ mole

(ii) Sodium is monoatomic

$\therefore$ Moles of $Na$ atoms= moles of $Na$ present

$=\frac{23}{23}=1$ moles

(iii) Calcium is monoatomic

$\therefore$ Moles of $Ca$ atoms= $\frac{40}{40}=1$ moles

(iv) Lithium is monoatomic

$\therefore$ Moles of $Li$ atom= $\frac{1.4}{7}=0.2$ mole

(v) Sulphur exists as $S_8$ molecule

$\therefore$ Moles of atoms of $S=8\times$ moles of $S_8=8\times \frac{32}{32\times 8}=1$ mole.