units of K

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Katie Bart 1I
Posts: 104
Joined: Sat Aug 24, 2019 12:16 am

units of K

Postby Katie Bart 1I » Wed Jan 08, 2020 11:42 pm

Why does the equilibrium constant not have units?

BritneyP- 2c
Posts: 101
Joined: Sat Sep 14, 2019 12:15 am

Re: units of K

Postby BritneyP- 2c » Wed Jan 08, 2020 11:46 pm

K doesn't have units because because the products and reactants have the same units so they can cancel out. But if it doesn't cancel out, instead of thinking of concentration or partial pressure, consider transition of reactants to products as activity, which is unitless, so K is unitless

Christineg1G
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Joined: Fri Aug 09, 2019 12:15 am
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Re: units of K

Postby Christineg1G » Thu Jan 09, 2020 9:19 am

Equilibrium constants don't have units because we used the active masses of the substances, hence why they are unit less/eliminated from the equilibrium constant expression.

RichBollini4G
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Joined: Wed Sep 18, 2019 12:18 am

Re: units of K

Postby RichBollini4G » Thu Jan 09, 2020 9:37 am

BritneyP- 2c wrote:K doesn't have units because because the products and reactants have the same units so they can cancel out. But if it doesn't cancel out, instead of thinking of concentration or partial pressure, consider transition of reactants to products as activity, which is unitless, so K is unitless


Thank you!

Suraj Doshi 2G
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Joined: Fri Aug 02, 2019 12:15 am

Re: units of K

Postby Suraj Doshi 2G » Thu Jan 09, 2020 9:40 am

K doesn't have units as the actual calculation comes from the chemical activity value. This value is a number without units therefore in the end, K does not have any units associated with it.

Caitlyn Tran 2E
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Joined: Fri Aug 09, 2019 12:15 am

Re: units of K

Postby Caitlyn Tran 2E » Thu Jan 09, 2020 9:40 am

We went over this in class a little bit, but there is also a section in the textbook that explains this if you would like to reference this in case my explanation does not make sense. Essentially, the equilibrium constant is the ratio between the activity of the products and the activity of the reactants. Since we are assuming an ideal situation, the activity is equal to the concentration or partial pressure of the products and reactants. While the concentration and partial pressure of substances have units, we leave them out since the activity of products and reactants do not have units. Hope this helps!

Jialun Chen 4F
Posts: 108
Joined: Sat Sep 07, 2019 12:16 am

Re: units of K

Postby Jialun Chen 4F » Thu Jan 09, 2020 9:57 am

Since it's a constant, not a variable, K does not have a unit. We can also think of this by perceiving the molarity units of products and reactant cancels.

105335337
Posts: 103
Joined: Sat Aug 24, 2019 12:15 am

Re: units of K

Postby 105335337 » Thu Jan 09, 2020 10:00 am

There are no units for K as the units tend to cancel out.

005321227
Posts: 90
Joined: Sat Sep 07, 2019 12:15 am

Re: units of K

Postby 005321227 » Thu Jan 09, 2020 12:27 pm

K does not have units. because it is a ratio of products to reactants, and is a constant in the reaction. Also, if you worked out the math in an equilibrium problem K = [P]/[R], and so the molarities cancel out.

Max Madrzyk Dis 4G
Posts: 102
Joined: Wed Sep 18, 2019 12:21 am

Re: units of K

Postby Max Madrzyk Dis 4G » Thu Jan 09, 2020 12:29 pm

The equilibrium constant does not have units because they cancel out when you are calculating it.

Joanne Lee 1J
Posts: 100
Joined: Thu Jul 25, 2019 12:15 am

Re: units of K

Postby Joanne Lee 1J » Thu Jan 09, 2020 1:04 pm

When you are finding the K, the units of the products and reactants are either all molarity, partial pressure, etc so all the units will cancel out when K is found.


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