Question

$150\, mL$ of $0.5 \,N$ nitric acid solution at $25.35^{\circ} C$ was mixed with $150\, mL$ of $0.5 \,N$ sodium hydroxide solution at the same temperature. The final temperature was recorded to be $28.77^{\circ} C$. Heat of neutralisation of nitric acid with sodium hydroxide

• A. -12.64 kcal
• B. -11.98 kcal
• C. -13.68 kcal
• D. -12.68 kcal

Answer 1

Answer: (C)

Total mass of solution $=150+150$
$=300 \,g$
$Q=$ Total heat produced $=300 \times(28.77-25.35)$ cal
$=300 \times 3.42=1026 \,cal$
Heat of neutralisation $=\frac{Q}{150} \times 1000 \times \frac{1}{0.5}$ $=\frac{1026}{150} \times 1000 \times \frac{1}{0.5}$
$=13.68\, kcal$
Since, heat is liberated, heat of neutralisation should be negative.
Hence, $\Delta H_{\text {neut }}=-13.68\, kcal$.