K and Q

[Jarrett Peyrefitte 2K]

When do you use Q and when do you use K? What are the differences between them?

[Esha Chawla 2E]

When do you use Q and when do you use K? What are the differences between them?

K is the equilibrium constant. Q is calculated the same way as K, but it can be used at any time - regardless of if the reaction is at equilibrium or not. By comparing the two, you can find the direction the reaction is favoring at the time. If Q > K, the reactants are favored, and the reaction proceeds backward. If Q < K, the products are favored, and the reaction proceeds forwards.

[Emma Popescu 1L]

Q is the reaction quotient. It can be used to determine which direction a reaction will shift to reach equilibrium based on the value of K, the equilibrium constant. If Q = K then the system is already at equilibrium.

[Areli C 1L]

From an earlier post, I learned that K is for a reaction that is at equilibria or the equilibrium constant. Q is calculated to determine where the reaction will proceed, Forward or Reverse since the rxn is not at equilibrium.

[Lauren Tanaka 1A]

The difference between K and Q is that K is only used when the reaction is at equilibrium and you know it is at equilibrium. Q, on the other hand, is when you are unsure whether the reaction is in equilibrium and you have to compare that value of Q to the K value that you will be given.

[Harry Zhang 1B]

You use Q when the reaction is not in equilibrium and you use K when the reaction is in equilibrium.

[Alexandra Bartolome 2H]

You use K when calculating the equilibrium constant when the reaction is at equilibrium. Q is the reaction quotient used to determine whether a reaction not at equilibrium will favor reactants or products.

[preyasikumar_2L]

K is the equilibrium constant which is calculated when the system is at equilibrium, and Q is the reaction quotient that can be calculated at any point in the reaction. They are both calculated in the same manner though and by comparing the Q and K values you can determine where the reaction lies.

[RichBollini4G]

When do you use Q and when do you use K? What are the differences between them?

K is the equilibrium constant. Q is calculated the same way as K, but it can be used at any time - regardless of if the reaction is at equilibrium or not. By comparing the two, you can find the direction the reaction is favoring at the time. If Q > K, the reactants are favored, and the reaction proceeds backward. If Q < K, the products are favored, and the reaction proceeds forwards.

Thank you!

[105335337]

If the question asks you to solve for the equilibrium constant, that is when you use Kc. If the question asks you to determine whether the reaction is at equilibrium or will proceed forwards/backwards, that's when you compare Kc to Q

[Juana Abana 1G]

Use K when the reaction is at equilibrium.
Use Q at any point in the reaction (when the reaction is not at equilibrium).

[Abigail_Hagen2G]

K is when the reaction is at equilibrium. Q is at all other points in the reaction, and can be used to show which direction the reaction is proceeding.

[005321227]

Q can be used whether or not the reaction is at equilibrium, and is used to determine whether or not a reaction is in equilibrium. K can only be used when a reaction is in equilibrium. Both are calculated in the same way.

[Max Madrzyk Dis 4G]

K is the equilibrium constant and is used when the reaction is in equilibrium, Q is the reaction quotient and can be used whether or not the reaction is in equilibrium.