Question

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

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

Answer 1

Answer: (A)

(i) At. wt. of $P=31$ and atomicity of $P$ is $4$
Mol. wt. of white $P=31\times 4=124$
$\therefore 6.023\times 10^{23}$ molecules of white $P$ weigh $124g$
$\therefore 3.0115\times 10^{23}$ molecules of white $P$ weigh
$\frac{124}{6.023}\times 3.015$
$=62g$
(ii) Wt. of $1$ mole of $H_2$ gas $=2g$
Wt. of $10$ moles of $H_2$ gas $=2\times 10=20g$
(iii) $1g$ molecule of anhydrous $N{a}_{2}C{O}_3=$ Mol wt. of $N{a}_{2}C{O}_3$ in $g=106g$
(iv) At STP $22.4LC{O}_2$ weighs $44g$
$\therefore 33.6LC{O}_2$ weighs $\frac{44}{22.4}\times 33.6g$
$=66g$
So, the correct choice
$ii<i<iv<iii$