First of all remember what the equilibrium constant.This - a quantity characterizing the ratio of the concentrations (or partial pressures) of reaction to the concentration of the starting substances.For example, if the reaction proceeds according to the scheme: A + B = C + D, the Cr = [C] [D] / [A] [B].
If the reaction scheme is as follows: 2A + B = 2C, the Kr is calculated by the following formula: [C] ^ 2 / [B] [A] ^ 2.That is, the indices are converted into index of the extent to which the need to build concentration of a particular component.
Consider an example.Suppose runs the very first reaction: A + B = C + D. is required to determine the equilib
rium concentrations of all the components, if it is known that the initial concentration of the starting materials A and B are equal to 2 mol / liter, and the equilibrium constant can be taken as one.
again write down the formula of the equilibrium constant for this particular case: Cr = [C] [D] / [A] [B].Given that Kr = 1, get: [C] [D] = [A] [B].
initial concentrations of substances A and B are known to you (defined under the terms of the problem).Initial concentrations of the reaction products C and D are equal to 0, and then increased to some equilibrium value.Designate the equilibrium concentration of substance C in x, then the equilibrium concentration of compound A (which was formed from C) is equal to (2).
As the reaction scheme shows that 1 mole of a substance and the image of one mole of C and from 1 mole of a substance B - 1 mole of substance D, then, respectively, the equilibrium concentration of D is also to be = xand the equilibrium concentration of V (2).
Substituting these values into the formula, receive: (2) (2) = x ^ 2.Solving this equation, we get: 4 = 4, that is, x = 1.
Consequently, the equilibrium concentration of the reaction products C and D is equal to 1 mol / liter.However, since the equilibrium concentration of the starting materials A and B are calculated according to the formula (2), then they will also be equal to 1 mol / liter.The problem is solved.