Question

The number of grams of oxygen in $32.2g$ of $N{a}_{2}S{O}_4$. $10H_{2}O$ is approximately

• A. $32.2g$
• B. $22.41g$
• C. $11.2g$
• D. $64.4g$

Answer 1

Answer: (B)

Number of oxygen in one molecule of
$N{a}_{2}S{O}_4\cdot lo{H}_{2}O=4+10=14$
Thus, moles of oxygen in ' $n$ ' mole of compound is $14n$
Molar mass of $N{a}_{2}S{O}_4\cdot 10H_{2}O=46+32+64+180$ $=322g/mol$
Thus, $\frac{\text{ weight of compound }}{\text{ molar mass of compound }}=\frac{32.2}{322}=0.1mol$
Now, moles of oxygen $=0.1\times 14=1.4$
So, weight $=$ moles $\times$ molar mass $=16\times 1.4=22.4g$