Question

Arrange the following in order of increasing mass
(i) $3.0115\times {10}^{23}$ molecules of white phosphorus $\left(P_4\right)$
(ii) $10$ moles of $H_2$ gas
(iii) $1g$ molecule of anhydrous $N{a}_{2}C{O}_3$
(iv) $33.6L$ of $C{O}_2$ gas at S.T.P

• A. $ii<i<iv<iii$
• B. $iii<vi<i<ii$
• C. $i<ii<iv<iii$
• D. $i<iv<iii<ii$

Answer 1

The correct option is A $ii<i<iv<iii$

(i) Atomic weight of P = $31u$
Atomicity of $P$ in white $P$ is 4
Therefore, molar weight of white $P=31\times 4=124g$
$\therefore 6.023\times {10}^{23}$ molecules of white P weigh 124 g
$\therefore 3.0115\times {10}^{23}$ molecules of white P weigh 62 g

(ii) Weight of 1 mole of $H_{2}gas=2\times 1=2$ g
weight of 10 moles of $H_{2}gas=2\times 10=20$ g

(iii) Mass of 1 g molecule of anhydrous $N{a}_{2}C{O}_3=$ molar weight of $N{a}_{2}C{O}_3$ in g = $23\times 2+12+16\times 3g=106g$

(iv) At STP 22.4 L $C{O}_2$ weighs 44 g
$\therefore 33.6LC{O}_2$ weighs $\frac{44}{22.4}\times 33.6\text{g}=66\text{g}$
So, the correct choice is $ii<i<iv<iii$