Measuring Enthalpy Change · Paper 1 — Free Chemistry HL Practice Questions

A student reacts solid sodium hydroxide with dilute hydrochloric acid and records the temperature of the mixture rising from $21.0\ ^\circ\text{C}$ to $28.5\ ^\circ\text{C}$. However, the student notes that dissolving solid NaOH in water is itself exothermic. Which statement correctly identifies the overall thermal observation and its thermochemical interpretation for the neutralisation experiment?

A student dissolves a solid salt in water at $20\ ^\circ\text{C}$. After stirring, the solution temperature falls to $14\ ^\circ\text{C}$. Which statement correctly describes thermochemistry of the dissolving process?

An energy profile for a reaction shows the reactants at a higher energy level than the products, with the arrow representing $\Delta H$ pointing downward from reactants to products. Which statement correctly describes this reaction?

A student adds $0.327\ \text{g}$ of zinc powder ($M_r = 65.4$) to $50.0\ \text{cm}^3$ of $0.200\ \text{mol dm}^{-3}$ copper(II) sulfate solution in a calorimetry experiment. The initial temperature is $21.0\ ^\circ\text{C}$ and the final temperature is $26.3\ ^\circ\text{C}$. The specific heat capacity and density of the solution are $4.18\ \text{J g}^{-1}\text{K}^{-1}$ and $1.00\ \text{g cm}^{-3}$ respectively. What is the enthalpy change, in $\text{kJ mol}^{-1}$, for the reaction below? $$\text{Zn(s)} + \text{CuSO}_4\text{(aq)} \rightarrow \text{ZnSO}_4\text{(aq)} + \text{Cu(s)}$$