Question

2. The standard free energy of formation of gaseous hydrogen iodide is 1.30 kJ/mol at 25°C. Find Kp for the reaction H2(g) + 12(8) = 2HI(g) at this temperature. A) 7.0 B) 7100 C) 1.0 D) 2.4 E) 2.9 Ans: E Category: Medium Section: 17.6

Answer 1

2)

H2(g) + I2 (s)   <------------> 2 HI (g)

standard free energy , delta Go = 1.30 kJ/mol

delta Go = - R T ln Kp

1.30 = - 8.314 x 10^-3 x 298 x ln Kp

Kp = 0.59

Note : there is no answer in the given options. so please check it once

Answer 2

H2 (g) + I2 (s) <-------> 2I (g)

Delta G = 1.30 kj/mole

delta G = - RTln(Kp)

You have 2I (g) so delta G = 2.60 kj/mole

ln(Kp) = - delta G/RT

ln(Kp) = -2.60 kj.mole / (0.0083145 kj/mole x 298 K) = 1.049656843

K = e^1.049656843 = 2.856670663 = 2.9 (answer E to question above)