Equibrium question calculate concentration

For the equilibrium

H2(g) + CO2(g) --><-- H2O(g) + CO(g)

Kc = 3.180 at 1106K. If each of the four species was initially present at a concentration of 3.000 M, calculate the equilibrium concentration of the H2(g) at this temperature. Give your answer in units of mol/L

Ok this is how I would have done it, Initially you have a concentration of 3.000 for all reagents and products, lets assume at equilibrium, x moles of CO2 has reacted ok...

So at equilibrium if x moles of CO2 has reacted, moles of reagents and products would be as follows:

mol of H2 = 3 - x
mol of CO2 = 3 - x
mol of water = 3 + x
mol of CO = 3 + x

Substitution of values in my equation formula, I'd have the following equation:

(3 + x)^2
_______ = 3.180
(3 - x)^2

So simplifying the whole equation by first square rooting the whole equation would give me:

(3 + x)
_____ = Square root of 3.180 = 1.783
(3 - x)

so, 3 + x = 1.783(3 - x),
2.783x = 1.783(3) - 3
2.873x = 2.349
x = 0.844 mol/dm3 = mol/L

Hence at equilibrium if amount of H2 or CO2 reacted is X amount remaining would be 3 - x

so [H2] at eqlbm = 3 - 0.844 = 2.156

no problem, chemistry is cool if you understand it...

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