Question

The hydrogen ion concentration of a solution prepared by diluting 50 mL of 0.10M $HN{O}_3\left(aq\right)$ with water to make it up to 500 mL is :

• A. 0.0010 M
• B. 0.0050 M
• C. 0.010 M
• D. 0.050 M
• E. 1.0 M

Answer 1

Answer: (C)

0.010 M

$HN{O}_3$ is a strong acid and completely dissociates in aqueous solution to give $H^{+}$.
Number of moles of $H^{+}=\frac{50mL}{1000mL/L}\times 0.10=0.005$ moles.
Total volume of the solution $=500mL=0.500L$.
(because 1 L = 1000 mL)
The hydrogen ion concentration $\left[H^{+}\right]=\frac{0.005}{0.500}=0.010M$.