CHEMISTRY COMMUNITY

What is the purpose of finding Q? Is it just to determine the direction of the reaction?

Yes, this is basically the only use.

Its useful to predict the direction of a reaction since you can find Q even if the system is not at equilibrium. If K is known, and you can measure Q, then you determine which side a reaction will favor until it reaches equilibrium. If Q<K, then the reaction will favor products until K is reached. If Q>K, then the reaction will favor reactants until K is reached.

Q, or the "reaction quotient", measures the relative amount of reactants and products at a certain time. It essentially describes a reaction when it's not in equilibrium and what direction will be taken for it for equilibrium to be restored (hence the favoring of a forward or reverse reaction)

If we are at the reaction equilibrium but we aren't sure would we use Q?

Q helps to determine or predict the path a reaction will take after a specific time. It can be compared to K to make assumptions about the reaction at hand.

You could calculate Q and if it matches K, then the reaction is at equilibrium.

To add on, since Q is the relative ratio of products to reactants at a given instant, you know the reaction shifts right if Q<K and shifts left if Q>K.When Q=K, the reaction is at equilibrium. To summarize, finding Q helps you determine what direction the reaction will proceed based on the ratio between products to reactants

Q expresses the relative ratio of products to reactants at a given instant not necessarily at equilibrium. This is mainly useful to compare to K in order to determine the direction of the reaction. When Q=K, the system is at equilibrium.

Q is the reaction quotient and tells us where the reaction is at currently relative to equilibrium. Note that for Q you do not need to use concentrations or partial pressures at equilibrium. However, for K we do. If Q<K product formation is favored and if Q>K reactant formation is favored. When Q=K the reaction is at equilibrium.

Q is the composition of a system at any time (even those other than equilibrium). It is an important indicator that tells you whether equilibrium lies in favor of products or reactants. when Q < K, the reaction will move toward the products, and if Q > K, the reaction will move towards the reactants, and if Q= K, the reaction is at equilibrium.