At what temperature is the following reaction at equilibrium when all substances are at standard pressure?

assume that entropies and enthalpies of reaction do not vary with temperature.
pcl3(g) + cl2(g) pcl5(g) substance ∆hºf , kj mol–1 sº, j mol–1 k –1 pcl3(g) –288.7 311.6 cl2(g) 0 223.1 pcl5(g) –374.9 364.2 (a) 506 k (b) 1640 k (c) 1980 k (d) 4260 k

The correct answer is option A.

Explanation:

Enthalpy of formation of gas =

Enthalpy of formation of chlorine gas =

Enthalpy of formation of gas =

The equation used to calculate enthalpy change is of a reaction is:  

For the given chemical reaction:

Entropy of of gas =

Entropy of chlorine gas =

Entropy of gas =

The equation used to calculate enthalpy change is of a reaction is:  

The equation used to calculate enthalpy change is of a reaction is:  

The equation for the entropy change of the above reaction is:

At equilibrium ,

1 kJ = 1000 J

At 506 K reaction will be at an equilibrium.