Question

For a particular reaction, ΔH° is 67.7 kJ and ΔS is 126.9 J/K. Assuming these values change very little with temperature, over what temperature range is the reaction spontaneous in the forward direction?For a particular reaction, ΔH° is 67.7 kJ and ΔS is 126.9 J/K. Assuming these values change very little with temperature, over what temperature range is the reaction spontaneous in the forward direction?

Answer 1

The forward reaction is spontaneous above 533 K.

Step-by-step explanation:

A reaction is spontaneous when the standard Gibbs energy of the reaction (ΔG°) is negative. ΔG° is related to the standard enthalpy of the reaction (ΔH°) and the standard entropy of the reaction (ΔS°) through the following expression.

ΔG° = ΔH° - T.ΔS°

where,

T is the absolute temperature

When ΔG° < 0,

ΔH° - T.ΔS° < 0

ΔH° < T.ΔS°

T > ΔH° / ΔS° = (67.7 × 10³ J) / (126.9 J/K) = 533 K

The forward reaction is spontaneous above 533 K.