IB Chemistry HL 1.4.2 Gibbs energy (ΔG) Question Bank

Practise IB Chemistry HL 1.4.2 by applying gibbs energy (δg) to exam-style questions.

[Maximum number: 2]

Nitrous acid, $\mathrm{HNO}_{2}$ , is a weak acid which can be used to make acidic buffers.

The overall reaction for the synthesis of ethyl ethanoate from ethane is:

2 \mathrm{C}_{2} \mathrm{H}_{6}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g})+\frac{3}{2} \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{2}(\mathrm{~g})+2 \mathrm{HCl}(\mathrm{~g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{~g})

Calculate the Gibbs energy change, $\Delta G^{\theta}$ in $\mathrm{kJ} \mathrm{mol}^{-1}$ , for this reaction under standard conditions. Use the value of $-4 \mathrm{~kJ} \mathrm{~mol}^{-1}$ for $\Delta H^{\theta}{ }_{\mathrm{r}}$ and your answer from (d)(iv). If you did not obtain an answer for (d)(iv) use $-10 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}$ , although this is not the correct answer. Use sections 1 and 4 of the data booklet.

conversion to common units
$\begin{aligned} \left\langle\Delta G^{\theta}=-4 \mathrm{~kJ} \mathrm{~mol}^{-1}-298 \mathrm{~K}^{-} 0.008 \mathrm{~kJ} \mathrm{~K}^{-1} \mathrm{~mol}^{-1} »\right. -6.4 « \mathrm{~kJ} \mathrm{~mol}^{-1} » \text { ↓ } \end{aligned}$

M1 is for conversion to common units M2 is for correct value.

Award [2] for correct final answer. If $-10 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ is used, the answer will be -1.0 « $\mathrm{kJ} \mathrm{mol}^{-1}$ ».

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1.4.2 (HL)—Gibbs energy (ΔG) question 1