The balance between enthalpy change and entropy change determines the feasibility of…

CHEMISTRY · Multi-part · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

The balance between enthalpy change and entropy change determines the feasibility of a reaction. Table 4 contains enthalpy of formation data and entropy data for some substances. Table 4
N 2 (g)O 2 (g)NO(g)C(graphite)
ΔHf/kJ mol−1\Delta H_f / \text{kJ mol}^{-1}00+90.40
S/J K−1mol−1S / \text{J K}^{-1}\text{mol}^{-1}1922052116
(1) Explain why the entropy value for oxygen is much greater than the entropy value for carbon (graphite). (2) Consider the following reaction that can lead to the release of the pollutant NO into the atmosphere. 12N2(g)+12O2(g)⟶NO(g)\frac{1}{2} \text{N}_2(\text{g}) + \frac{1}{2} \text{O}_2(\text{g}) \longrightarrow \text{NO}(\text{g}) Use data from Table 4 to calculate the minimum temperature at which this reaction becomes feasible.

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