chem
posted by jj on .
In an equilibrium mixture of HCl, Cl2 and H2, the partial pressure of H2 is 4.2 mPa and that of Cl2 is 8.3 mPa. What is the partial pressure of HCl at 500 oK given that at that temperature Kp = 4.0 x 1018 for
H2(g)+ Cl2(g)> 2HCl(g)

*** I meant Kp = 4.0 x 10^18

If Kp = 4.0E18 = (HCl)^2/(H2)(Cl2)
Isn't this just a matter of substituting values for (H2) and (Cl2) and solving for (HCl)? Or is it more complicated than that. 
yes i did that but the answer i get is weird

True you obtained a huge number for (HCl); however, with a K as large as 10^18 you know (HCl) must be very very large.

Is 8.35 x 10^9mPa the right answer?

@DrBob222: is that the answer?