[sassy]

Hi guys!  I'm having some trouble with the following question, please could anyone help?

Consider the following equilibrium 2Cl₂(g) + 2H₂O(g)  4HCl(g) + O₂(g) for which Kp=0.752 at 480°C

1) What is the value of Kp for the reaction: 2HCl(g) + 0.5O₂(g)  Cl₂(g) + H₂O(g)

2) What is the value of Kc for the above reaction in (1)

My answer for question 1 was Kp = 1.15 and for the second question I got Kc = 9.04

I really don't think that these are correct answers, please could someone help?

Thank you!

[AWK]

The first answer seems to be OK.
Show your calculations for the second problem. Which value or R did you use.

[sassy]

The first answer seems to be OK.
Show your calculations for the second problem. Which value or R did you use.

I used R = 0.0821
My calculations were as follows:

Kp=KcRT(to the power of delta n)
Kc= Kp/RT(to the power of delta n)
n = 2 -2.5 = -0.5
Kc=1.15/[0.0821x(480 + 273)](to the power of -0.5)
Kc =9.04

Is this correct?

[AWK]

OK, I checked for the first reaction, not for that one in point 1.
R=0.08206 - you result should contain 3 significant digits, hence we do not abreviate constants (but four digits is sufficient). It is formalism, probably square root minimize this error.

[sassy]

OK, I checked for the first reaction, not for that one in point 1.
R=0.08206 - you result should contain 3 significant digits, hence we do not abreviate constants (but four digits is sufficient). It is formalism, probably square root minimize this error.

Thanks for your help   

[docnet]

The Kp for the reverse reaction would simply be the reciprocal of the forward reaction. Dividing the coefficients of a reaction by 2 would have no effect on the equilibrium constant. Only a change in temperature can affect the equilibrium constant.

In calculating Kc, I think the delta n you should be using is -1, instead of using -0.5, for similar reasons.