Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

$50\ \text{cm}^3$ of $2.50\ \text{mol dm}^{-3}$ hydrochloric acid was poured into a polystyrene beaker with negligible heat capacity. Its temperature was measured, after which $50\ \text{cm}^3$ of $2.50\ \text{mol dm}^{-3}$ NaOH at the same temperature was added rapidly, with stirring. The temperature increased by $17\ ^\circ\text{C}$. For the purposes of the calculation, the final solution can be treated as having a specific heat capacity of $4.2\ \text{J g}^{-1}\ \text{K}^{-1}$. What approximate value would you obtain for the molar enthalpy change of neutralisation of hydrochloric acid and sodium hydroxide from this experiment?

  • A$-\dfrac{50 \times 4.2 \times 17}{0.050 \times 2.5}\ \text{J mol}^{-1}$
  • B$-\dfrac{50 \times 4.2 \times 17}{0.10 \times 2.5}\ \text{J mol}^{-1}$
  • C$-\dfrac{100 \times 4.2 \times 17}{0.050 \times 2.5}\ \text{J mol}^{-1}$
  • D$-\dfrac{100 \times 4.2 \times 17}{50 \times 2.5}\ \text{J mol}^{-1}$

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