Chemistry 9701 · AS & A Level · Chemical energetics
Chemical energetics — practice question
The table presents selected standard entropy data. When lead(IV) oxide, $\text{PbO}_2$, is heated, it breaks down into lead(II) oxide, $\text{PbO}$, and oxygen. $\text{2PbO}_2(s) \rightarrow \text{2PbO}(s) + \text{O}_2(g)$, $\Delta H^{\circ} = +118\,\text{kJ mol}^{-1}$.
(a)[2]
Using the data, calculate the value of $\Delta S^{\circ}$ for this reaction. $\Delta S^{\circ} = \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ \text{J K}^{-1}\text{ mol}^{-1}$.
(b)[3]
Use the value of $\Delta H^{\circ}$ and your answer to (a) to calculate the temperature at which this reaction becomes feasible. $T = \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots\ \text{K}$.
(c)[1]
Solid lead(II) oxide can be produced by heating lead metal in air. Predict the sign of the standard entropy change for this reaction. Explain your answer.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Correct stoichiometric approach” …