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### K and Q

Posted: Wed Jan 08, 2020 2:22 pm
When do you use Q and when do you use K? What are the differences between them?

### Re: K and Q

Posted: Wed Jan 08, 2020 2:25 pm
Jarrett Peyrefitte 2K wrote: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.

### Re: K and Q

Posted: Wed Jan 08, 2020 2:47 pm
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.

### Re: K and Q

Posted: Wed Jan 08, 2020 5:53 pm
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.

### Re: K and Q

Posted: Wed Jan 08, 2020 7:02 pm
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.

### Re: K and Q

Posted: Wed Jan 08, 2020 7:10 pm
You use Q when the reaction is not in equilibrium and you use K when the reaction is in equilibrium.

### Re: K and Q

Posted: Wed Jan 08, 2020 9:31 pm
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.

### Re: K and Q

Posted: Wed Jan 08, 2020 9:45 pm
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.

### Re: K and Q

Posted: Thu Jan 09, 2020 9:35 am
Esha Chawla 2E wrote:
Jarrett Peyrefitte 2K wrote: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!

### Re: K and Q

Posted: Thu Jan 09, 2020 10:03 am
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

### Re: K and Q

Posted: Thu Jan 09, 2020 11:28 am
Use K when the reaction is at equilibrium.
Use Q at any point in the reaction (when the reaction is not at equilibrium).

### Re: K and Q

Posted: Thu Jan 09, 2020 11:44 am
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.

### Re: K and Q

Posted: Thu Jan 09, 2020 12:20 pm
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.

### Re: K and Q

Posted: Thu Jan 09, 2020 12:23 pm
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.