Question

How many grams of a 70% concentrated nitric acid solution sholud be used to prepare $250mL$ of $2.0MHN{O}_3$ solution?

• A. $54.0\text{g}$
• B. $45.0\text{g}$
• C. $90.0\text{g}$
• D. $70.0\text{g}$

Answer 1

The correct option is B $45.0\text{g}$

$M=\frac{W\times 1000}{M_w\times V_{\text{solution}}\left(mL\right)}$

$2=\frac{W_{HN{O}_3}\times 1000}{63\times 250}$

$W_{HN{O}_3}=31.5\text{g}$
$70\%HN{O}_3$ means $70\text{g}HN{O}_3$ is present in $100\text{g}$ solution.
$\therefore 31.5\text{g}HN{O}_3$ will be present in $\frac{100}{70}\times 31.5$
$=45\text{g}$ of solution

Hence, the correct answer is option (b).