K vs Q

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Zaynab Hashm 2I
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K vs Q

Postby Zaynab Hashm 2I » Fri Jan 10, 2020 3:16 pm

can someone please explain the reason why when;

1) Q<K, there is more reactant

2) Q>K, there is more product

anything explaining what results in Q<K or Q>K would help!

Alex Tchekanov Dis 2k
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Re: K vs Q

Postby Alex Tchekanov Dis 2k » Fri Jan 10, 2020 3:27 pm

So to understand this, you have to understand the equation. K is the product over the reactant at equilibrium. Q is also the product of the reactant.. but not at equilibrium.
Therefore when Q<K, how could that be? Well if you look at the formula, it means that Q must have more reactants because it's in the denominator, thus since there's more reactants than before, to reach equilibrium it has to now shift towards the products. Vice versa for the other way around.

Pegah Nasseri 1K
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Re: K vs Q

Postby Pegah Nasseri 1K » Fri Jan 10, 2020 3:45 pm

Knowing that both K and Q are the ratios of products to reactants will help you determine which value has more products or more reactants than the other.

If Q<K then you would know that Q has less products than K, meaning that the reaction has more reactants than what it would have at equilibrium, so the reaction needs to proceed forward in order to produce more products which explains why the reaction shifts right.

If Q>K, then Q has more products than K, meaning that the reaction has more products than what it would have at equilibrium, so the reaction will proceed backwards to produce more reactant, which is why the reaction shifts left.

Hannah Pham
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Re: K vs Q

Postby Hannah Pham » Fri Jan 10, 2020 3:47 pm

Q measures the relative amounts of products and reactant present during a reaction at a particular point in time. Q is compared to K, the equilibrium constant, to determine which direction the reaction proceeds. If Q>K, then the reverse reaction is favored and if Q<K, then the forward reaction is favored.

Sally Qiu 2E
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Joined: Fri Aug 30, 2019 12:18 am

Re: K vs Q

Postby Sally Qiu 2E » Fri Jan 10, 2020 4:02 pm

the equation to calculate K and Q is the concentration of products over concentration of reactants. If Q is less than K, that means that there must be more reactants compared to the concentrations at equilibrium. Therefore, the reaction will shift to the right to produce more products. the same logic would apply when Q is greater than K: there are more products and the reaction must shift to the left to produce more reactants.

Kylie Lim 4G
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Re: K vs Q

Postby Kylie Lim 4G » Fri Jan 10, 2020 4:34 pm

When Q>K, the numerator or [P] is larger for Q than K which means there are more products at the time Q is being calculated than there are at equilibrium. In order to compensate for the larger concentration of products, the reaction will produce more reactants and the reverse reaction is favored. When Q<K there are more reactants, so the forward reaction is favored to produce more products.

Anna Heckler 2C
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Re: K vs Q

Postby Anna Heckler 2C » Fri Jan 10, 2020 4:50 pm

Q can be thought of as a snapshot of the reaction concentrations at a moment in time. K is a value that does not change, remaining the same throughout the whole reaction. If Q is greater than K, there is more product than would be found when the reaction is at equilibrium, so the reaction will proceed in the reverse direction. The opposite is true for if Q was less than K.

ABombino_2J
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Re: K vs Q

Postby ABombino_2J » Fri Jan 10, 2020 10:51 pm

When Q is less than K there are more reactants because a larger denominator in [products]/[reactants] will lead to a smaller value Q. Therefore, this reaction will shift to the right to regain equilibrium. When Q is greater than K there are more products because a larger numerator in [products]/[reactants] will lead to a larger value Q. Therefore, this reaction will shift to the left to regain equilibrium.

Daniel Yu 1E
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Joined: Sat Aug 24, 2019 12:15 am

Re: K vs Q

Postby Daniel Yu 1E » Sat Jan 11, 2020 10:27 pm

The Q and K inequality is exactly that: an inequality. K is the ratio of the concentration of products and the concentration of reactants. Q is the exact same equation, [p]/[r]. Given a certain set of physical conditions, the K will always be the same number for a given reaction. This is because K is the equilibrium constant, the constant obtained when both the concentration of products and the concentration of reactants are constants. What this means is that the forward reaction and the reverse reaction are occurring at the same rate, hence why the concentrations aren't changing (or changing negligibly). This is the definition of chemical equilibrium. In the same scenario, however, Q is not always the same number. Q is obtained instead of K when using the [p]/[r] equation when the result is not the specific K value. Therefore, to determine what direction the reaction is favoring, compare Q to K. If Q < K, the reaction sits to the left because there are more reactants then products. Vice versa if Q > K

005324438
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Joined: Sat Aug 24, 2019 12:16 am

Re: K vs Q

Postby 005324438 » Sun Jan 12, 2020 4:46 pm

Q is just a method to determine which way the reaction is going to go. The equation has products over reactants, so when there are more products, Q is larger, when there are more reactants Q is smaller. If we let any reaction sit for a while, it will eventually reach K, this means that if Q>K, there are more products than there should be, and the reaction will shift left in order to correct that. If Q<K, there are more reactants than there should be, and the reaction will shift right.


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