Difference between K and Q?

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Diana Chavez-Carrillo 2L
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Difference between K and Q?

Postby Diana Chavez-Carrillo 2L » Fri Jan 17, 2020 11:19 pm

The reaction quotient (Q) formula looks very similar to the formula used for the equilibrium constant, K so what is their difference? Is it just that K has to be at equilibrium or is there other differences between them?

Samuel G Rivera - Discussion 4I
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Re: Difference between K and Q?

Postby Samuel G Rivera - Discussion 4I » Sat Jan 18, 2020 12:33 am

Q and K have the exact same formula. Q can be any value depending on the state of the reaction. K is Q when the reaction reached equilibrium.

Jamie Hwang 2F
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Re: Difference between K and Q?

Postby Jamie Hwang 2F » Sat Jan 18, 2020 1:47 am

Yeah, K is at equilibrium while Q is at any stage of the reaction.

205405339
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Re: Difference between K and Q?

Postby 205405339 » Sat Jan 18, 2020 10:24 am

K represents the concentrations at equilibrium whereas Q represents concentrations not at equilibrium

AKhanna_3H
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Re: Difference between K and Q?

Postby AKhanna_3H » Sat Jan 18, 2020 10:55 am

Q and K are both measured by the ratio of products over reactants, but K represents that ratio at equilibrium while Q can represent that ratio at any point in the reaction.

905373636
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Re: Difference between K and Q?

Postby 905373636 » Sat Jan 18, 2020 11:31 am

K is a fixed value for the reaction, while Q varies if the reaction is/is not yet at equilibrium and we can compare the two values to determine if the reaction is at equilibrium or not.

Emma Joy Schaetz 1E
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Re: Difference between K and Q?

Postby Emma Joy Schaetz 1E » Sat Jan 18, 2020 11:44 am

Is the formula always the same for Q and K? I know whether we use Q or K depends on the equilibrium status of the reaction, but we find the values the exact same way otherwise?

vibha gurunathan 1h
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Re: Difference between K and Q?

Postby vibha gurunathan 1h » Sat Jan 18, 2020 1:36 pm

The formula's the same and you find it in the same way, but you use current concentrations/pressures for Q and equilibrium concentrations/pressures for K.

EthanPham_1G
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Re: Difference between K and Q?

Postby EthanPham_1G » Sat Jan 18, 2020 4:22 pm

K is the equilibrium constant and can only be solved for when the concentrations of reactants and products at equilibrium are known. Q is the reaction quotient and can be solved at any point in the reaction, regardless if it is in equilibrium. If Q<K then the reaction moves forward and favors the products. If Q>K then the reaction moves reverse and favors the reactants.

Alexandra Bartolome 2H
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Re: Difference between K and Q?

Postby Alexandra Bartolome 2H » Sun Jan 19, 2020 12:30 am

Q is calculated the same was as K. However, K is the equilibrium constant while Q is the reaction quotient at any time during the reaction. You compare Q to K in order to find out whether the reaction is at equilibrium or not. When Q<K, the forward reaction is favored since the concentration of reactants is higher than the concentration of products. When Q>K, the reverse reaction is favored. If Q=K, the reaction is at equilibrium.

Andres Merlos 2L
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Re: Difference between K and Q?

Postby Andres Merlos 2L » Sun Jan 19, 2020 1:25 pm

They look very similar because the only difference between the two constants is when you should use them. You use K when the reaction is at equilibrium, and you use Q at any stage of the reaction. You can compare the two constants to determine which way the reaction is shifting.

Lauren Stack 1C
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Joined: Sat Aug 17, 2019 12:18 am

Re: Difference between K and Q?

Postby Lauren Stack 1C » Sun Jan 19, 2020 2:25 pm

Q and K are actually calculated using the same formula with products over reactants. The difference between the two lies in when they apply. K ONLY applies to when a reaction has reached equilibrium. On the other hand, Q can represent any time during a reaction. Using Q, you an determine if the reaction is at equilibrium (K=Q) or what direction the reaction is moving in depending on if K>Q or K<Q.


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