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Q.
The number of grams of oxygen in $32.2 \,g$ of $Na _2 SO _4$. $10 H _2 O$ is approximately
TS EAMCET 2021
Solution:
Number of oxygen in one molecule of
$Na _2 SO _4 \cdot loH _2 O =4+10=14$
Thus, moles of oxygen in ' $n$ ' mole of compound is $14 n$
Molar mass of $Na _2 SO _4 \cdot 10 H _2 O =46+32+64+180$ $=322 g / mol$
Thus, $\frac{\text { weight of compound }}{\text { molar mass of compound }}=\frac{32.2}{322}=0.1 mol$
Now, moles of oxygen $=0.1 \times 14=1.4$
So, weight $=$ moles $\times$ molar mass $=16 \times 1.4=22.4 g$