Difference between K and Q

$PV=nRT$

ursulavictorino1K
Posts: 55
Joined: Sun Feb 17, 2019 12:15 am

Difference between K and Q

What is the difference between the significance of K and Q if it is the same formula to find each value?

Ryan Yoon 1L
Posts: 55
Joined: Mon Jul 01, 2019 12:15 am

Re: Difference between K and Q

Although K, the equilibrium constant, and Q, the reaction quotient, uses the same formula to find the value, they are not the same. The concentrations of reactant and product in K are in equilibrium, while the concentrations of reactant and product in Q have yet to reach equilibrium.

haileyramsey-1c
Posts: 105
Joined: Thu Jul 25, 2019 12:18 am

Re: Difference between K and Q

K represents the equilibrium constant when the reaction is in equilibrium. Q represents the reaction quotient and is the quotient of activities of products and reactants. Typically you compare the determined q value to a given k value to determine which direction the reaction proceeds.

Eva Zhao 4I
Posts: 101
Joined: Sun Sep 29, 2019 12:16 am

Re: Difference between K and Q

To add on, since Q expresses the relative ratio of products to reactants at a given instant not necessarily at equilibrium, you know the reaction shifts right if Q<K and shifts left if Q>K.

Justin Quan 4I
Posts: 104
Joined: Sat Sep 14, 2019 12:17 am

Re: Difference between K and Q

In addition, if K=Q, the reaction is in equilibrium because the ratio of products to reactants is equal to the equilibrium constant.

Catherine Daye 1L
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

Re: Difference between K and Q

K is used for when the reaction is at equilibrium, while Q is used for when the reaction is not. A reaction at equilibrium moves at a different rate than when it’s not at equilibrium. Therefore, they’re different numbers that you can compare to determine which direction the reaction favors.

William Chan 1D
Posts: 102
Joined: Sat Sep 14, 2019 12:15 am

Re: Difference between K and Q

K, the equilibrium constant, is a constant, which at some set conditions, is a constant at equilibrium. Q is calculated the same way but is calculated to see whether the reaction proceeds forward or backward to reach equilibrium.

ThomasNguyen_Dis1H
Posts: 102
Joined: Fri Aug 30, 2019 12:17 am

Re: Difference between K and Q

K is the equilibrium constant with the equilibrium values of the product and reactants. Q is used when the reaction is not at equilibrium and is used to predict what's favored as the reaction proceeds.

gabbymaraziti
Posts: 111
Joined: Wed Sep 18, 2019 12:19 am

Re: Difference between K and Q

Q can be taken at any point in a reaction while K is taken when the reaction has reached equilibrium. If K = Q, then the reaction was in equilibrium at the time Q was taken. K and Q can be compared to each other in order to determine if the forward or reverse reaction is favored.

Angela Prince 1J
Posts: 102
Joined: Sat Aug 24, 2019 12:17 am

Re: Difference between K and Q

Q is the reaction quotient, which is the ratio of the reaction at any given time, not just when the system is at equilibrium.