L+M=======2N has an equilibrium constant of 25 at STP.?

Question

Calculate the equilibrium concentrations of L, M, and N if a system containing, initially, 2 mol of L and 2 mol of M dissolved in 24 dm3 of a suitable solvent, is allowed to reach equilibrium at STP.

Answer 1

First, to cut through the crap, 1 dm3 is a liter. So, the initial conc are 0.083 Mol/lit. If x mol/lit reacts to reach equilibrium, 2x of N will be in solution.
Then:
[2x]^2 / [0.083-x]^2 = 25
Unlike reactions with a very low value of K, you can't ignore x in the denominator. You can trial and error to a solution without much hassle, for a starting point, try x = 0.05.