Question

A sample of ammonium phosphate $(N{H}_4{)}_{3}P{O}_4$ contains $3.18$ moles of $H$ atoms. The number of moles of $O$ atoms in the sample is:

• A. $0.265$
• B. $0.795$
• C. $1.06$
• D. $3.18$

Answer 1

The correct option is C $1.06$

$149\text{g}$ of $(N{H}_4{)}_{3}P{O}_4$ contains $12\text{g}$ of $H$.
For $3.18$ moles of $H$ i.e. $3.18\text{g}$ of $H$,
$3.18\text{g}$ of $H$ present in $\frac{149\times 3.18}{12}=39.5\text{g}(N{H}_4{)}_{3}P{O}_4$.
$149\text{g}$ of $(N{H}_4{)}_{3}P{O}_4$ contains $64\text{g}$ of Oxygen.
$\therefore 39.5\text{g}$ of $(N{H}_4{)}_{3}P{O}_4$ will contain $\frac{64\times 39.5}{149}\text{g}$ oxygen= $16.96\text{g}$ oxygen.
i.e. $16.96\text{g}$ oxygen present in the sample.
$\therefore$ Number of moles of oxygen $\frac{16.96}{16}=1.06\text{moles}$