Question

1000 g impure sample of NaOH contains 3 mol of oxygen atoms. The $\%$ purity of the sample is:

• A. $14\%$
• B. $12\%$
• C. $100\%$
• D. $24\%$

Answer 1

The correct option is B $12\%$

Moles of NaOH = moles of oxygen atoms
Mass of NaOH = $3\times 40=120g$
$\therefore$ $\%$ $\text{purity}=\frac{\text{mass of NaOH}}{\text{mass of impure sample}}\times 100=12\%$