Reactant Quotient vs Equilibrium Constant

[Kishan Shah 2G]

How can you identify when to calculate a reactant quotient vs an equilibrium constant. Also, are the rules for calculating them the same (ex: do you omit solids and liquids for reactant quotient as well?)

[christabellej 1F]

The rules for calculating both the reaction and equilibrium constant would be the same. You would calculate the equilibrium constant when the reaction is at equilibrium and calculate the reaction quotient at any other point of the reaction.

[Brian Tangsombatvisit 1C]

You would calculate the reactant quotient when you want to determine whether the reaction will proceed in the forward or the backward direction, assuming that the reaction is currently not at equilibrium. If the reactant quotient is greater than the equilibrium constant, then the reaction will proceed in the reverse direction. If the reactant quotient is less than the equilibrium constant, then the reaction will proceed in the forwards direction.

In other words, the reactant quotient is calculated the same way as the equilibrium constant, but is only calculated at one point during the reaction, not during equilibrium.

[Jessica Kwek 4F]

You would calculate the reactant quotient the same way that you calculate the equilibrium constant. You solve for the reactant quotient when the reaction is not at equilibrium. The equilibrium constant is calculated when the reaction is at equilibrium.