[LovesOrganic]

Hello everyone! I'm having some trouble with a problem concerning adsorption kinetics. So, here it is :
Consider a process A+B C+D
1) At standard conditions an equimolar mixture of A and B are passed over a catalyst. Assume the catalyst is 95% efficient and the mixture reaches equilibrium. What's the ΔG° for this reaction?
2) Assume large surface of catalyst is available intially. In the table you'll find several p₀ and initial rates. Find the missing rate.

pA, bar			pB, bar			rC, bar*s-1
0.10			0.90			4*10-4
0.15			0.85			5.6*10-4
0.25			0.75			8.2*10-4
0.3			0.7			??

The first part was standard and I obtained a value of ΔG°=-13.4 kj/mol.
For the second part... I'm very confused and not sure where to start from. If this were a simple reaction (without adsorption), I'd try finding the rate law. Actually, I have tried this but got values that are not whole and differ depending on which values I choose, hence I believe this to be the wrong approach.

I've done some reading around and found this equation
[itex]r=\frac{k_r\alpha_A\alpha_B p_A p_B}{(1+\alpha_A p_A+\alpha_B p_B)^2}[/itex]
I could write three such equations and solve a system of simultaneous equations but even wolfram couldn't solve it.
And that's where I am stuck right now. Any help would be highly appreciated