K vs. Q

[Lilly Catarozoli 1B]

Hi! Just to clarify, Q and K are both the ratio of products over reactants, the only difference is that Q is used when the reaction is not at equilibrium? Thanks!

[SalmaQ]

Hello Lilly!
The time when we would use the reaction quotient (Q) would be any time during the reaction and like you stated, the K constant is used for when at an equilibrium! Hope this helps!

[Karl Yost 1L]

Exactly! Q is just [P]/[R] at any given time. When Q = K, then we say the reaction is at equilibrium.

[SalmaQ]

And yes to clarity both have the same ratio [Products]/[Reactants].

[Sabrina Galvan 3J]

Yup! They are both calculated the same way, and Q is used as a way to compare the state of the system and whether what direction the reaction is going relative to the value of K.

[Jiapeng Han 1C]

Q could be used at anytime of a reaction that is happening, it is just the ratio of products to reactants. However, K shall only be used when the reaction reaches equilibrium.

[Akriti Ratti 1H]

Hi! What you wrote is correct. We call Q the reaction quotient.

[Rajshree 1F]

yes, Q is the ratio of [P]/[R] when the system is not at equilibrium (K)

[Krish_Ajmani_3J]

You are exactly right. Q=[P]/[R] but can be used even if the system is not in equilibrium.
Some important things to keep in mind regarding Q and K:
Q=K at equilibrium.
If Q<K, the reaction will go forward/towards products.
If Q>K, the reaction will go backward/towards reactants.

[Simi Kapila_3E]

Yes, Q is used anytime the reaction is not in equilibrium and K is only used when the reaction is in equilibrium. You can use the Q value to comparatively to the K value, to see where you are in the reaction (to see if it needs to shift right or left).

[Sophia Spungin 2E]

They are calculated the same way, however when calculating K the concentrations of product and reactants must be those at which the reaction is at equilibrium, whereas the concentrations of products and reactants used to calculate Q can be from any given point at which the reaction is occurring.

[Melis Kasaba 2B]

Yes, that is correct. Q is the reaction quotient and K is the equilibrium constant. We use Q to figure out which direction a reaction will shift to reach equilibrium. If K > Q, the forward reaction is favored, converting reactants into products. If K < Q, the reverse reaction is favored, converting products into reactants. If K = Q, we know the system is at equilibrium and neither the forward nor reverse reaction is favored; instead they proceed at equal rates.

[Liam Bertrand 3]

Yes, Q just applies to a reaction that is not at equilibrium, while K is at equilibrium. You can compare the two values to determine which direction the reaction is going.

[Inderpal Singh 2L]

Yes! Q is when the reaction is not at equilibrium.

[Sean Wang 1F]

Yes, Q is the reaction quotinent. Use Q when the reaction is not at equilibrium and use K when the reaction is at equilibrium.

[Jason Knight - 1F]

Q is the reaction quotient of the reaction and can be used to analyze the state of the system. It is important to note both Q and K are calculated with the same formula, but when calculating Q we do not know the state of the system necessarily. If Q>K then the reverse reaction is favored, and if Q<K then the forward reaction is favored. If Q=K, which is rare, then we can say the reaction is at equilibrium.

[Ava Nickman]

yup! that's correct

[Carly_Lipschitz_3H]

K is used only when the reaction is at equilibrium. Q is used when we are unsure whether or not the reaction is at equilibrium. Although Q can be equal to K (meaning the reaction at that point is at equilibrium), Q can also be greater than or equal to K. K is a constant, whereas Q is not.

[Rylee Mangan 1K]

We would use Q when the reaction has been disrupted/ no longer in equilibrium right?

[keely_bales_1f]

So if we are given Kc and then are told to calculate Q with the given concentrations of the products and reactants, Q would tell us if the reaction is at equilibrium or if the reaction leans toward the products/reactants?

[Amanda Chang 2B]

So if we are given Kc and then are told to calculate Q with the given concentrations of the products and reactants, Q would tell us if the reaction is at equilibrium or if the reaction leans toward the products/reactants?

Yup, that's right!

[dana hu 1B]

Q is a quantity that changes as a reaction system approaches equilibrium. (have not yet reached equilibrium; reaction in progress)
K is the numerical value of Q at the "end" of the reaction when equilibrium is reached.

[Logan Wiedemann 3J]

Yep, you've got it! Q is just when the reaction isn't at equilibrium!

[Bryan Le 2K]

Yes! Q is used when the system hasn't reach equilibrium yet while K is used when the system has reach equilibrium.

[Tatyana Bonnet 2H]

Yes Q is used at any time to see where the reaction is at in relation to equilibrium and K is the constant value at equilibrium. If Q=K then it is at equilibrium.

[Brenda Silva 1B]

Yes, Q and K are both the ratio of [products]/ [reactants] and the only difference is that K is used when equilibrium has been reached and Q is used anytime the reaction is occurring.

[Margaret Xu 3C]

Hi Lilly! You are correct. The reaction quotient, Q, is used to represent the concentration/partial pressure of products divided by the concentration/partial pressure of reactants of the reaction at ANY time. The equilibrium constant, K, represents the reaction at equilibrium.

[Kyle Dizon 3A]

Correct. Product divided by reactants will determine the K. If reaction is not at equilibrium, Q can be determined in order to identify if the reactant or products will be favored.

[Shalyn Kelly 3H]

Hi! You're correct! K is when the system is at equilibrium and Q is when the system is not, so if Q=K then the system has reached equilibrium.

[Joel Meza 3I]

Yes, that's correct, Q is just the ratio at any time during the reaction and K (equilibrium constant) is the ratio when the reaction is at equilibrium.

[Kat Stahl 2K]

Yep you're right Q is when the reaction is not at equilibrium and K is when it is at equilibrium, but it is the same calculation.

[Emma Strassner 1J]

Yes, Q and K are both the same process of using the ratio of products to reactants. The only difference is that Q is when the reaction is not at equilibrium.

[Daniela Santana 2L]

Yes you are correct. Q is used when they are not equilibrium values yet. You can find Q at any time during the reaction but K is only when the reaction is at equilibrium.

[Isabella Cortes 2H]

Yes, you are correct! Q is found the same way as K and you use Q when the reaction has not reached equilibrium.

[Madilyn Schindler 3E]

Yes, both Q and K are calculated using the same method. The only difference is that K is the ratio of concentrations when the system is at equilibrium. Q is the ratio of concentrations when the system isn't at equilibrium.

[jia207]

K is used when a reaction is at equilibrium and Q is used when an equation is not over equilibrium. They are both always Products/Reactants

[Claudia_Danysh_2B]

Yes! Just to clarify even more, Q is the reaction quotient while K is the equilibrium constant!

[Sofia Lombardo 2C]

Q and K are both calculated using the [p]/[r]. Q is the reaction quotient, and is used at any time where the reaction is not at equilibrium. K is for when the reaction is at equilibrium.

[Zainab Jamali 1H]

You're correct! I believe Q can be calculated at any time during the reaction (including at equilibrium) but if it is specified that the reaction is at equilibrium you can use K instead.

[Karen Zheng_2K]

K is only used when a system is in equilibrium (K=Q)!

[Aria Movassaghi 1A]

Yes, it is the same equation but k is at equilibrium.

[Mansi Solanki 3A]

You're right! The K is used for the system when it is in equilibrium while Q can be used at any point in time for the system.

[Gian Boco 2G]

Yep, Q is just the expression anytime during the expression wheres as K is the value for when it is in equilibrium.

[LeahSWM 2E]

Yes, K is used when the equation is at equilibrium while Q is when it is not.

[Mina Tadros 3L]

Correct. Whenever you take the ratio of the concentration (or partial pressure) of products over reactants when it is not at equilibrium, you are solving for Q, the reaction quotient. If the reaction is at equilibrium, then the ratio of products to reactants is the equilibrium constant, K.

[Brandon McClelland3L]

Q represents products/reactants in general, while K only represents products/reactants at equilibrium.

[Daniel Hernandez 1G]

They are both calculated the same way however Q reflects the state of the reaction whereas K represents the reaction at equilibrium.

[TiffanyBrownfield 2I]

Yes Q and K are essentially the same thing. The only difference is that K is the concentration of products and reactants when it is at equilibrium and Q is at any time during the reaction. Q's value relative to K can be used to determine the direction that the reaction is tending towards.

[Rayna Irving 2C]

Q and K are found the exact same way with the ratio of products/reactants, but K is just specifically referring to the value when the reaction reaches equilibrium.

[Devan Nathu - 2H]

Just to clarify, will we always be able to assume that the reaction is at equilibrium when K=Q? Thanks!!

[Mehreen 3I]

Hi! Just to clarify, Q and K are both the ratio of products over reactants, the only difference is that Q is used when the reaction is not at equilibrium? Thanks!

Yes, exactly! The Q is known as the reaction quotient and it is used when the reaction is not at equilibrium (all other times).

[Caelin Brenninkmeijer 1G]

They are both calculated using the same method ([P]/[R]), but Q represents the reaction at any time while K represents the reaction at equilibrium.

[Gwen Casillan 3E]

Just to clarify, will we always be able to assume that the reaction is at equilibrium when K=Q? Thanks!!

Yes, since K is the equilibrium constant, when Q (the reaction quotient) is equal to K, the reaction is at equilibrium.

[sabrina ghalambor 2J]

Q is P/R at any time during the reaction and we can use it to determine which reaction is favored.