JEE Advanced 2017 Paper 2

ΔG°=−RTlnK,ΔG° =ΔH°−TΔS°
−RTlnK=ΔH°−TΔS°, lnK=−

ΔH°

R

1

T

+

ΔS°

R

ΔH°<0,ΔS°>0⇒ K decreases with increases in T;ΔH>0,ΔS°>0⇒K increases with increase in T
ΔH°>0,ΔS°<0⇒ K decreases with increases in T;ΔH<0,ΔS°>0⇒K decreases with increase in T
ΔSsurr=−

qsys

Tsurr

ΔSsurr favourable means ΔSsurr is positive while ΔSsurr unfavourable means ΔSsurr is negative. If value of Kincreases with increase in temperature for endothermic reaction it means reaction shift toward forward directionbecause of unfavourable change in entropy of the surrounding decreases. Similarly if value of K for exothermic reaction decreases with increase in temperature it means reaction shift toward backward direction due to decrease in favourable change in entropy of surrounding.