Question

How many grams of concentrated nitric acid solution should be used to prepare 250 mL of 2.0 M $HN{O}_3$?
(The concentrated acid is 70 % $HN{O}_3$ by weight)

• A. 90 g
• B. 45 g
• C. 70 g
• D. 54 g

Answer 1

The correct option is B 45 g

$Molarity=\frac{\text{moles of solute of}HN{O}_3}{\text{total volume of solution (mL)}}\times 1000$
$\Rightarrow 2=\frac{\text{moles of solute of}HN{O}_3}{250}\times 100$
Moles of solute = 0.5 moles
Mass of 0.5 moles = moles $\times$ molar mass of $HN{O}_3=0.5\times 63=31.5$ g
Mass of $HN{O}_3$ in 70 % concentrated acid =$\frac{31.5}{70}\times 100=45$ g