To determine the enthalpy change of neutralisation for hydrochloric acid, $20\,\mathrm{cm^3}$ of solution that contains $0.04\,\mathrm{mol}$ of $\mathrm{HCl}$ is put into a plastic cup with negligible heat capacity. A $20\,\mathrm{cm^3}$ portion of aqueous sodium hydroxide containing $0.04\,\mathrm{mol}$ of $\mathrm{NaOH}$, and initially at the same temperature, is then added, causing the temperature to increase by $15\,\mathrm{K}$. If the heat capacity per unit volume of the final solution is $4.2\,\mathrm{J\,K^{-1}\,cm^{-3}}$, what is the enthalpy change of neutralisation of hydrochloric acid?
- A$\dfrac{20 \times 4.2 \times 15}{0.04}\,\mathrm{J\,mol^{-1}}$
- B$40 \times 4.2 \times 15 \times 0.08\,\mathrm{J\,mol^{-1}}$
- C$\dfrac{40 \times 4.2 \times 15}{0.04}\,\mathrm{J\,mol^{-1}}$
- D$\dfrac{20 \times 4.2 \times 15}{0.08}\,\mathrm{J\,mol^{-1}}$