[big]

4 HBr(g) + O₂(g)  2 Br₂(g) + 2 H₂O(g)     K_c=88.5 at 500°C

The value of K_p for the above reaction is:
A) 13.9  B) 21.6  C) 885  D)5.62*10⁴

Correct me if I am wrong, but isn't the equation for this: K_p=K_c(RT) ^{:delta: n}?

So shouldn't it be K_p=(88.5)(0.0821L*atm/mol*K*88.5K)^-1=12.2? Why is it not any of the answer choices?

[UG]

The temperature is 773 K not 88.5 K, but changing this doesn't give a correct answer either
Maybe they used a different value of R (one that is 10 magnitudes smaller)?

[big]

The temperature is 773 K not 88.5 K, but changing this doesn't give a correct answer either
Maybe they used a different value of R (one that is 10 magnitudes smaller)?

Oh right, thanks for catching that! But the thing is, I looked up a derivation of the formula a little bit back and I thought that they had used 0.0821? 

[Borek]

Kp in this case should have a pressure^-1 units. If units are not given you can't say anything about the value.

I would try with R in SI units. No guarantee of success though.