Question

In the decomposition of ozone, O3, what is the value of /\G_rxn at 25*C for the pressures shown below?

2O3 (g) --> 2O2 (g) + O (g)

PO3 = 1400 mm Hg PO2= 30 mm Hg PO= 15 mm Hg

Answer 1

The balance reaction is as follows:

2O3 (g) --> 2O2 (g) +2 O (g)

Given that PO3 = 1400 mm Hg PO2= 30 mm Hg PO= 15 mm Hg

First calculate the value of Kp as follows:

Kp = product / reactants

= [30]^2 [15]^2 / [1400]^2

= 900*225/1960,000

= 0.103

We know that;

ΔG^o = –RT In K_(eq)

      or  ΔG^o = –2.303 RT log K_(eq)

here R = 8.314 J/K mo, T = 25C or 298 K

therefore;

ΔG^o = –2.303 RT log K_(eq)

= - 2.303 * 8.314 *298 log 0.103

= -5705.85 ( -0.986)

= +5625.34 J / mole

= + 5.63 KJ/ mole