In: Chemistry
Consider the reaction: X2(g)→2X(g). When a vessel initially containing 714 torr of X2 comes to equilibrium at 298 K, the equilibrium partial pressure of X is 116 torr . The same reaction is repeated with an initial partial pressure of 777 torr of X2 at 707 K ; the equilibrium partial pressure of X is 561 torr
Find delta H for the reaction (in kJ/mol)
X2(g) ---- 2X(g)
Initial 714 0
Final (714-x) 2x
2x = 116 torr
x = 58 torr
X2 = 714 - 58 = 656 torr
Kp1 = [X]^2/[X2] = (116)^2/656 = 20.512
X2(g) ---- 2X(g)
Initial 777 0
Final (777-x) 2x
2x = 561 torr
x = 280.5 torr
X2 = 777 - 280.5 = 496.5 torr
Kp2 = [X]^2/[X2] = (561)^2/496.5 = 633.879
Using the claussius clapeyron equation we get
ln(kp2/kp1) = DeltaH/R * (1/T1 - 1/T2)
ln(633.879/20.512) = Delta H/8.314 * (1/298 - 1/707)
Delta H = 14693.33 J/mol = 14.693 KJ/mol