Q and direction

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Alfred Barrion 2H
Posts: 100
Joined: Sat Jul 20, 2019 12:16 am

Q and direction

Postby Alfred Barrion 2H » Sun Jan 12, 2020 3:56 pm

How does Q let us predict the direction that an equilibrium practice will go through?

JohnWalkiewicz2J
Posts: 103
Joined: Thu Jul 11, 2019 12:17 am
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Re: Q and direction

Postby JohnWalkiewicz2J » Sun Jan 12, 2020 4:00 pm

Typically if Q<K, then the reaction will proceed from left to right (reactants→products)
If Q>K, then the reaction will proceed from right to left (reactants←products)

Julie Park 1G
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

Re: Q and direction

Postby Julie Park 1G » Sun Jan 12, 2020 4:03 pm

K describes the equilibrium constant (the ratio of products and reactants at equilibrium). By comparing Q (the ratio of products and reactants at a specific instant, not necessarily at equilibrium) with K, you can tell which way the reaction will proceed to get closer to equilibrium.
For example, when Q<K, the reaction will shift right. Here, the ratio of prod/react at that particular instant is smaller than K. By looking at the relationship between the numerator(prod) and denominator(react), this means that the amount of product present is smaller (than at K). Therefore, the reaction will "go to the right" to increase the amount of product and achieve a Q that is closer to K.

Julie_Reyes1B
Posts: 105
Joined: Sat Jul 20, 2019 12:16 am

Re: Q and direction

Postby Julie_Reyes1B » Sun Jan 12, 2020 4:05 pm

To add on to John, my high school chemistry teacher gave us a good way to remember which way the reaction will go. If you write K and Q in alphabetical order, then the less-than and greater-than symbols will point in the direction of the reaction. For example K>Q looks like it is pointing to the right, telling you that the reaction will tend towards products.

Radha Patel 4I
Posts: 97
Joined: Tue Feb 12, 2019 12:15 am

Re: Q and direction

Postby Radha Patel 4I » Sun Jan 12, 2020 4:22 pm

When Q < K at the same time during the reaction then R > P and the forward reaction is favored
When Q > K at the the same time during the reaction , then P > R and reverse reaction is favored.
When Q = K at the same time during the reaction then it is at equilibrium.


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