Effect of Adding Reactants (11.1)

[Emily Glaser 1F]

In the solutions manual for 11.1 (c) is states that the value of the K constant is not affected by the amounts of reactant or products added. How is this. I understand concentrations determine the K constant, but a concentration is determined by moles and volume.

[Curtis Tam 1J]

I think this is actually related to the le chatelier's principle which is beyond 11.8. When you have a greater concentration of reactant, for example, more product will be produced to "minimize the effect of the stress" to maintain the same Kc value.

[Michelle Nguyen 2L]

The K constant is the ratio of products to reactants at equilibrium; it therefore does not change for the same reaction under the same conditions (e.g. temperature) no matter what the initial concentrations are. Thus, when we add product or reactant to the system, we will see the concentrations of substances shift to regain equilibrium, that is, to regain the ratio of products to reactants denoted by K. Since K remains constant, concentrations must change to accommodate the introduced substance and return to equilibrium composition.