Given the two reactions

PbCl2⇌Pb2++2Cl−, K3 = 1.83×10−10, and
AgCl⇌Ag++Cl−, K4 = 1.15×10−4,

what is the equilibrium constant Kfinal for the following reaction?

PbCl2+2Ag+⇌2AgCl+Pb2+

Question

Given the two reactions

    PbCl2⇌Pb2++2Cl−,   K3 = 1.83×10−10, and
    AgCl⇌Ag++Cl−,   K4 = 1.15×10−4,

what is the equilibrium constant Kfinal for the following reaction?

PbCl2+2Ag+⇌2AgCl+Pb2+

anonymous · Answer

First you need to find a way to add the reactions that you have constants for in a way to make it equal the final reaction.

There are several rules when combining equilibrium constants. If you have a constant k, then if you reverse a reaction, the constant is then 1/k. If you multiply a reaction by a number(such as doubling or tripling each reactant and product), you raise the constant k to that power (k^2 or k^3). Lastly when combining two or more reactions, you take the product, so if you have constants ka and kb, the constant k(a+b) is ka * kb.