Consider the reaction X Y at 300 K. If H and K are 28.40 kJ mol-1 and 1.8 10-7 at the same temperature, then the magnitude of S for the reaction in J K-1 mol-1 is . (Nearest integer) (Given : R = 8.3 J K-1 mol-1, ln 10 = 2.3, log 3 = 0.48, log 2 = 0.30)
Answer
34
Solution
G = -2.303RT K
log K = log(1.8 × 10-7) = log 18 − 7 − 1 = log 18 − 8
log 18 = log 2 + 2 log 3 = 0.30 + 0.96 = 1.26 ⇒ log K = −6.74
⇒ G = -2.3 8.3 300 (-6.74)
⇒ G = +38600 J mol-1
G = H - T S
⇒ S = H - G T
⇒ S = 28400 - 38600300
⇒ S = −34 J K-1 mol-1
∴ Magnitude of S = 34
Answer: 34