Question

2 reacts with the halogens (X2) according to the following reaction:
H2(g)+X2(g)?2HX(g)
where X2 can be Cl2, Br2, or I2.

Reactant/Product	?H?f(kJ/mol)	?S?f(J/mol?K)
H2(g)	0	130.7
Cl2(g)	0	223.1
HCl(g)	-92.3	186.9
Br2(g)	30.9	245.5
HBr(g)	-36.3	198.7
I2(g)	62.42	260.69
HI(g)	26.5	206.6

Assuming deltaG^o for the reaction between hydrogen and Cl2 is -190.46 kJ calculate Kp for the reaction between hydrogen and Cl2.

Answer 1

Frist let us calculate the delta H and delta S for the reaction by using the relation,

delta Hreaction = delta Hproducts - delta Hreactants

                         = 2 x -92.3 - (0 + 0)

                         = -184.6 kJ/mol

delta Sreaction = delta Sproducts - delta Sreactants

                         = 2 x 186.9 - (130.7 + 223.1)

                         = 20 kJ/mol.K

We know, delta Greaction = delta Hreaction - T x delta Sreaction

                -190.46 = -184.6 - (T x 20)

or T = 0.293 K

Now, delta G = -RT lnKp

-190.46 = -(8.314 x 0.293) ln Kp

Kp = 9.03 x 10^33