1. There is this really simple question regarding calculating the Kc value at equilibrium.

I will show you how I worked it out, and you can tell if what I did is correct, because I'm told by my friend that I should get a different answer.

Chemical Equation: I2 + H2 = 2HI ; H<0 (i.e. forward reaction is exothermic)

Initial:
2 mol of Iodine, 0 mol of Hydrogen and 8 mol of HI.

At equiblibrium:
It is found that there is 4 mol HI left.

Volum = 0.5dm^3
WORKING OUT:

HI:

Inital = 8
Change = -4
Mol at equilibrium = 4
Concentration at equilibrium: 8M

I2:

Inital = 2
Change = +2
Mol at equilibrium = 4
Concentration at equilibrium: 8M

H2:

Inital = 0
Change = +4
Mol at equilibrium = 2
Concentration at equilibrium: 4M

Therefore, Kc = [products]/[reactants].

Therefore, Kc = (8^2)/(8*4)

Kc = 2.

That is what I got as my answer.

However, someone tells me that the answer should be 0.5 (i.e. 1 / my answer), because apparently the reverse reaction is favoured.

However, I've never heard of this regarding the calculation of Kc.

Why would it be [I2][H2] / [HI]^2

That doesn't make sense, or am I missing something?

Thanks

2.

3. H2 Change is +2, not +4.

That was just a typo, never mind that.

Basically, the problem is that I get Kc = 2, and my friend gets Lc = 0.5 (i.e. 1 / my answer, because he says the reverse reaction is favoured).

Who is correct?

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