Q 11.49

[MadisonFuentes1G]

The correct answer to Q 11.43 in the book is c) K=x^2/(1.0-2x)^2. I was wondering why this is the case. I understand why the numerator is x^2, and I understand that the denominator has to do with the difference in stoichiometric coefficients, but I do not understand why 1.0-2x is squared or why there is 2x instead of x.

[Xuan Kuang 2L]

Hey there! I believe it has to do with the coefficient of the reactant, which has a 2 on it, I assume (Sorry, I'm not too sure about this because I don't think I have the same edition as you)

If there's a 2 as a coefficient, we have to consider this when forming the ICE Box. In this case, if the products change by x, then by the mole ratio in the balanced rxn, the reactant will therefore change by 2x because it's in a 2:1:1 ratio, so the equilibrium value is 1.0-2x. We also square it because of the 2 as a coefficient, so we raise the entire expression, 1.0-2x to the 2nd power in the denominator.

I hope this helps! :)