Question

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 0.0584 M, the concentration of N2 was 0.0195
M, and the concentration of NH3 was 0.430 M. What was the initial concentration of ammonia?

Answer 1

Calculate Kc by substituting the values from the problem into the Kc expression.
.........2NH3 ==> N2 + 3H2
I.........X........0.....0
C........-2Y.......Y.....3Y
E.....X-2Y..........Y....3Y
Eproblem..0.43.....0.0195..0.0584
So you know X-2Y = 0.430. Substitute the value of Y (that's N2 at equil) and solve for X. Interesting problem.

Answer 2

0.218