Ammonia is synthesized industrially by the reaction Thermodynamic data (all…

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

Problem

Ammonia is synthesized industrially by the reaction

\text{N}_2(g)+3\,\text{H}_2(g) \rightarrow 2\,\text{NH}_3(g)

Thermodynamic data (all quantities are molar and refer to standard states):

\Delta H^{\circ}=-92.4\,\text{kJ\,mol}^{-1}

and

\Delta S^{\circ}=-198\,\text{J\,mol}^{-1}\,\text{K}^{-1}

, each assumed to be temperature-independent over the range considered. (a) Calculate

\Delta G^{\circ}

for the reaction at

450\,\text{K}

. (b) Determine the equilibrium constant

K_{450}

450\,\text{K}

. (c) Repeat the calculations in parts (a) and (b) for

700\,\text{K}

to obtain

\Delta G^{\circ}

and

K_{700}

. (d) Use the results from parts (b) and (c) to explain how increasing temperature affects the position of equilibrium for the synthesis of ammonia. Relate your explanation to both the numerical values of

K

and the thermodynamic sign of

\Delta H^{\circ}

Related theory

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