Question

$50.0mL$ of $0.10M$ $HCl$ is mixed with $50.0mL$ of $0.10M$ $NaOH$. The solution temperature rises by ${3.0}^{o}C$. Calculate the enthalpy of neutralisation per mol of $HCl$.

• A. $-2.5\times {10}^{2}kJ$
• B. $-1.3\times {10}^{2}kJ$
• C. $-8.4\times {10}^{1}kJ$
• D. $-6.3\times {10}^{1}kJ$

Answer 1

Answer: (A)

$-2.5\times {10}^{2}kJ$

No. of moles of $HCl=5$ $milimoles$

No. of moles of $NaOH=5$ $millimoles$

Mass of solution mixed $=50$ $gm+50$ $gm=100$ $gm$

$\Delta H=-cm\Delta T(c=4.18$ $kJK{g}^{-1})$

$⟹\Delta H=-4.18\times 0.1\times 3$

$⟹\Delta H=-1.254$ $kJ$ (For $5$ $milimoles$ of water formed)

For $1$ $mole$ water $=\frac{-1.254}{5\times {10}^{-3}}=-2.5\times {10}^2$ $kJ$