K vs. Q

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hazelyang2E
Posts: 57
Joined: Fri Sep 28, 2018 12:23 am

K vs. Q

Postby hazelyang2E » Sat Jan 19, 2019 8:08 am

Could someone please explain to me the difference between K and Q, the reaction quotient? I'm just a little confused on the differences between the two as they are essentially calculated in the same way. Thank you!

klarratt2
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

Re: K vs. Q

Postby klarratt2 » Sat Jan 19, 2019 9:50 am

Both K and Q have the same equation ([products]/[reactants]).

K is the equilibrium constant. You use the equilibrium concentrations of the products and reactants to find it.

Q is the reaction quotient. For Q, the reaction is not at equilibrium. You use Q to compare the current reaction to the reaction when it is at equilibrium. By doing this, you can tell whether the concentration of reactants or products is greater and in which direction the reaction will proceed.

For example, if Q>K, it means that at that moment, there is a greater concentration of products than reactants (compared to when the reaction is at equilibrium). This means that the reaction will proceed to the left to make more reactants.

On the other hand, if Q<K, there is a greater concentration of reactants than products, which means the reaction will proceed to the right to make more products.

Sean Reyes 1J
Posts: 67
Joined: Fri Sep 28, 2018 12:24 am

Re: K vs. Q

Postby Sean Reyes 1J » Sat Jan 19, 2019 10:36 am

K is the equilibrium constant, meaning to calculate it, you must use equilibrium concentrations/partial pressures.
Q is the reaction quotient and is calculated the same way as K, except using non-equilibrium concentrations/partial pressures.
In comparing the two values (K and Q), you can find which direction a reaction will proceed in. For example, if K>Q, then the reaction will favor the creation of products and will thus favor the forward reaction.
Hope this helps !

Simmi Diwanji 2B
Posts: 32
Joined: Fri Sep 28, 2018 12:20 am

Re: K vs. Q

Postby Simmi Diwanji 2B » Sun Jan 20, 2019 2:51 pm

Q is very similar to K in that they are calculated the same way, but Q calculates the ratio of products/reactants at any given time, usually at initial concentrations or partial pressures. It is used to compare a reaction to its equilibrium constant K to see what side the reaction favors.

904914909
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

Re: K vs. Q

Postby 904914909 » Sun Jan 20, 2019 5:08 pm

K is the equilibrium constant, the proportion of products to reactants when the reaction is at equilibrium. Q is the reaction quotient and it show the proportion of products to reactants when the reaction is not at equilibrium.

Cienna Henry 1J
Posts: 61
Joined: Fri Sep 28, 2018 12:15 am
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Re: K vs. Q

Postby Cienna Henry 1J » Sun Jan 20, 2019 5:12 pm

It is also important to note that Q can be equal to K. In this case, the reaction is at equilibrium.


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