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Thermodynamics (A-level only)

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Question 9

This question is about thermodynamics. Consider the thermal decomposition of calcium carbonate shown below:

CaCO3(s)→CaO(s)+CO2(g) \text{CaCO}_3(\text{s}) \rightarrow \text{CaO}(\text{s}) + \text{CO}_2(\text{g}) CaCO3​(s)→CaO(s)+CO2​(g)

The table below shows some thermodynamic data.

SubstanceCaCO3(s)\text{CaCO}_3(\text{s})CaCO3​(s)CaO(s)\text{CaO}(\text{s})CaO(s)CO2(g)\text{CO}_2(\text{g})CO2​(g)
ΔfH⊖ / kJ mol−1\Delta_f H^\ominus\ /\ \text{kJ mol}^{-1}Δf​H⊖ / kJ mol−1−1207-1207−1207−635-635−635−394-394−394
S⊖ / J K−1mol−1S^\ominus\ /\ \text{J K}^{-1}\text{mol}^{-1}S⊖ / J K−1mol−1939393404040214214214
a.

Explain why the standard entropy value for carbon dioxide is greater than that for calcium carbonate.

[1]
b.

State the temperature at which the standard entropy of calcium oxide is 0 J K−1mol−10\ \text{J K}^{-1}\text{mol}^{-1}0 J K−1mol−1.

[1]
c.

Use the equation and the thermodynamic data provided to calculate the minimum temperature, in K\text{K}K, at which this reaction becomes feasible.

[7]

Thermodynamics (A-level only) Questions

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