[davie08]

4NH3 + 7O2  <----> 4NO2 + 6H20

Calculate keq. When the reactants are first mixed, their concentrations are [NH3]=1.800 M and [O2]=2.000 M. After mixing and when the system has reached equilibrium, [H2O]= 1.614 M

Would I just use the ICE chart, but how can I find the products without initial concentrations?

[davie08]

I think I over complicated this would it just be [H2O]^6  / [NH3]^4 + [O2]^7

[Corribus]

It would be helpful to know what states the reactants and products are in.  Is water a liquid, a gas, what?

[davie08]

all gas

[Corribus]

So you're dealing with pressures... it's odd to see that expressed as a Molarity.

Anyway, do they give you initial concentrations of the products?  If not, I think you have to assume zero.

[Borek]

Gas concentrations are OK, although rarely used.

Simply assume initial concentrations of everything that was not listed to be zero and use stoichiometry to calculate concentrations at equilibrium. You can assume volume of 1L if it will make calculations easier for you (in the end the volume should cancel out, so it doesn't matter what exact value you assume).

Note that your reaction quotient is wrong.