Chemistry 9701 · AS & A Level · Chemical energetics

Chemical energetics — practice question

(a)[1]

Complete Table 8.1 by placing a single tick ($\checkmark$) in each row to show the sign of every energy change under standard conditions.

(b)[1]

Define the enthalpy change of hydration.

(c(i))[3]

Choose and use the relevant information from Table 8.2 to determine the lattice energy, $\Delta H^{\circ}_{\text{latt}}$, of $\text{CaBr}_2(s)$. A labelled energy cycle may help. Show your working.

(c(ii))[2]

Use data from Table 8.2 together with your answer to (c)(i) to work out the standard enthalpy change of hydration, $\Delta H^{\circ}_{\text{hyd}}$, of $\text{Br}^-$. A labelled energy cycle may help. If you could not do (c)(i), take $-2500\,\text{kJ mol}^{-1}$ as $\Delta H^{\circ}_{\text{latt}}$ for $\text{CaBr}_2(s)$. Note that this is not the correct value. Show your working.

(c(iii))[2]

Explain why the enthalpy change of hydration of the $\text{Br}^-$ ion is more negative than that of the $\text{I}^-$ ion.

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Correct sign placement for lattice energy, hydration enthalpy and solution enthalpy

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI