Consider the following data for the reaction X2(g) + Y2(g) 2XY(g) at 600 K. The rG (in kJ mol-1) for the reaction is : array|c|c|c| Compound & fH 600 K ( kJ mol-1) & S 600 K ( J mol-1 K-1) \ XY(g) & 42 & 200 \ X2(g) & 8 & 140 \ Y2(g) & 80 & 250 \ array
- −21000
- −10
- −1000
- −9.012
Answer
(2) −10
Solution
rH = 2 fH (XY) - [ fH (X2) + fH (Y2)]
⇒ rH = 2(42) − (8 + 80) = −4 kJ mol-1
rS = 2S (XY) - [S (X2) + S (Y2)]
⇒ rS = 2(200) − (140 + 250) = +10 J K-1 mol-1 = 0.010 kJ K-1 mol-1
rG = rH - T rS
⇒ rG = −4 − 600 × 0.010
⇒ rG = −4 − 6 = −10 kJ mol-1
Answer: (2)