# Need chemistry help with a sample of ammonia gas that was allowed to come to equilibrium.

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A sample of ammonia gas was allowed to come to equilibrium at 400 K

2NH3(g)  N2(g) + 3H2(g)

At equilibrium, it was found that the concentration of H2 was 0.0591 M, the concentration of N2 was 0.0197 M, and the concentration of NH3 was 0.441M.  What is Kc for this equilibrium?

Select one:
Nov 8th, 2015

For the stated equilibrium between NH3, N2 and H2, we can write the following equilibrium equation:

Kc=[N2]*[H2]^3 / [NH3]^2

That is, the concentration of products, to the power of their reaction coefficients, divided by the concentration of the reactant, also to the power of its coefficient.

By replacing the given concentrations

Kc=(0,0197)*(0,0591)^3 / (0,441)^2 = 0,0197 * 0,0002064 / 0,19448  = 2,1*10^-5 (option c)

(I rounded up the values - as it is a multiple choice question it did not matter)

Hope this is clear. If not, please drop me a line and I'll get back to you.
Nov 8th, 2015

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Nov 8th, 2015
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Nov 8th, 2015
Nov 18th, 2017
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