Units for K

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Lizette Noriega 1H
Posts: 105
Joined: Wed Sep 18, 2019 12:15 am

Units for K

Postby Lizette Noriega 1H » Thu Jan 09, 2020 8:16 pm

Why doesn't K have any units?

EvanWang
Posts: 101
Joined: Sat Sep 07, 2019 12:16 am

Re: Units for K

Postby EvanWang » Thu Jan 09, 2020 8:17 pm

K is technically calculated using an attribute called the activity of a substance, and activity is unitless.

sarahforman_Dis2I
Posts: 109
Joined: Sat Aug 17, 2019 12:18 am

Re: Units for K

Postby sarahforman_Dis2I » Thu Jan 09, 2020 9:12 pm

In addition, because the activity is equal to a constant multiplied by the concentration, and often times that constant is equal to one under ideal conditions, we can assume that the concentration values are values of the activity. As someone stated above, activity values do not have units.

Diana Chavez-Carrillo 2L
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Joined: Fri Sep 28, 2018 12:18 am

Re: Units for K

Postby Diana Chavez-Carrillo 2L » Thu Jan 09, 2020 9:18 pm

To go off of the previous responses, although units are omitted when we write K we write a C or P next to it which indicates the units we are using without necessarily writing them. The purpose of this is to make sure that it is clear whether we are calculating concentration or pressure. For Kc, it indicates that we are using molar concentration units. For Kp, it indicates that you are using partial pressure with atm or bar as your unit to find the total pressure. This is why it's important when writing K to specify if its Kc or Kp.

DLee_1L
Posts: 103
Joined: Sat Aug 17, 2019 12:17 am

Re: Units for K

Postby DLee_1L » Fri Jan 10, 2020 10:11 am

K is just the ratio of the amount of product versus amount of reactant. So if the product is 20 M and the reactant is 5M at equilibrium the units (M) would cancel out and Kc would equal 4

Catherine Daye 1L
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Joined: Wed Sep 11, 2019 12:16 am

Re: Units for K

Postby Catherine Daye 1L » Fri Jan 10, 2020 10:24 am

The equilibrium constant K is the ratio of reactants to products, and ratios don’t have units.

ThomasNguyen_Dis1H
Posts: 102
Joined: Fri Aug 30, 2019 12:17 am

Re: Units for K

Postby ThomasNguyen_Dis1H » Fri Jan 10, 2020 11:13 am

Because it is a constant and is just a value used to look at the equilibrium of the reaction

805373590
Posts: 101
Joined: Wed Sep 11, 2019 12:17 am

Re: Units for K

Postby 805373590 » Fri Jan 10, 2020 1:27 pm

Since k is a ratio constant the units of the products and reactants concentration cancel out making k a unitless constant.

CynthiaLy4F
Posts: 103
Joined: Sat Jul 20, 2019 12:16 am

Re: Units for K

Postby CynthiaLy4F » Fri Jan 10, 2020 9:08 pm

K is unitless because it is the activities of products over the activities of reactants. Since activities do not have units, K will not have units.

Tahlia Mullins
Posts: 105
Joined: Thu Jul 25, 2019 12:15 am

Re: Units for K

Postby Tahlia Mullins » Fri Jan 10, 2020 10:32 pm

The combination of K being a measurement of activity as well as the fact that it is a constant, means that it does not have ay units.

McKenna_4A
Posts: 115
Joined: Sat Aug 24, 2019 12:18 am

Re: Units for K

Postby McKenna_4A » Sat Jan 11, 2020 6:44 am

K is a ration, so all units cancel


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