Kc and Kp

Moderators: Chem_Mod, Chem_Admin

amogha_koka3I
Posts: 62
Joined: Fri Sep 28, 2018 12:24 am

Kc and Kp

Postby amogha_koka3I » Fri Jan 11, 2019 7:45 pm

Are solids and liquids not included in calculating Kc AND Kp or just Kc?

Maya_Peterson1C
Posts: 62
Joined: Fri Sep 28, 2018 12:28 am

Re: Kc and Kp

Postby Maya_Peterson1C » Fri Jan 11, 2019 8:46 pm

We use Kp for gases, and it is calculated by using the partial pressures of those gases, so I don't believe this would apply to solids or liquids.

Karan Thaker 2L
Posts: 75
Joined: Fri Sep 28, 2018 12:26 am

Re: Kc and Kp

Postby Karan Thaker 2L » Fri Jan 11, 2019 9:34 pm

Gases as well as aqueous substances!

Chem_Mod
Posts: 17463
Joined: Thu Aug 04, 2011 1:53 pm
Has upvoted: 391 times

Re: Kc and Kp

Postby Chem_Mod » Fri Jan 11, 2019 10:08 pm

Pure liquids and solids are not included in the equilibrium equation. This is becasue they dont really have a concentration. On another note, please be aware that this doesn't mean water isnt included in the equilibrium equation. If a reaction involves water as a gas then it IS included in the equilibrium equation.

katie_sutton1B
Posts: 61
Joined: Fri Sep 28, 2018 12:17 am

Re: Kc and Kp

Postby katie_sutton1B » Sat Jan 12, 2019 8:56 am

Kp is only used for gases, so you won't be able to use liquids or solids for that reaction. But for reactions with liquids, solids, and aqueous, then no, you do not include liquids or solids. This is because a pure substance does not really have a concentration and therefore does not affect the equation.

005115864
Posts: 64
Joined: Fri Sep 28, 2018 12:15 am

Re: Kc and Kp

Postby 005115864 » Sat Jan 12, 2019 9:49 am

No they are not included in when solcing for Kc or Kp because and pure liquids don't have concentrations. Since solids and pure liquids aren't really mixed with other things, so that is why we can't really use them to calculate kc or kp. That is why it is ideal to use gases and aqueous solutions.

Rami_Z_AbuQubo_2K
Posts: 89
Joined: Thu Jun 07, 2018 3:00 am

Re: Kc and Kp

Postby Rami_Z_AbuQubo_2K » Sat Jan 12, 2019 10:36 am

The only thing included is aqueous solutions and gases but not liquids or solids. You cannot have a concentration of a liquid and pure liquids do not really react much so that amount that existed in the reactants will almost be the exact same in the products which will just cancel out in the calculation of the equilibrium constant.

KatelinTanjuaquio 1L
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am
Been upvoted: 1 time

Re: Kc and Kp

Postby KatelinTanjuaquio 1L » Sat Jan 12, 2019 1:20 pm

Solids and liquids are not used in equilibrium constants. Kc is used for concentrations while Kp is used for partial pressures. However, these can be converted between each other using the ideal gas law, PV=nRT.

Ana Pedreros
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

Re: Kc and Kp

Postby Ana Pedreros » Sat Jan 12, 2019 1:50 pm

If asked for the K expression, can Kc and Kp be used interchangeably?

Chloe Qiao 4C
Posts: 65
Joined: Fri Sep 28, 2018 12:27 am

Re: Kc and Kp

Postby Chloe Qiao 4C » Sat Jan 12, 2019 6:04 pm

Ana Pedreros wrote:If asked for the K expression, can Kc and Kp be used interchangeably?


I think the question will state clearly whether Kc or Kp is asked. If not, it will depend on the states of the substance involved in the reaction or the condition in the question.

BenJohnson1H
Posts: 68
Joined: Fri Sep 28, 2018 12:17 am

Re: Kc and Kp

Postby BenJohnson1H » Sat Jan 12, 2019 6:48 pm

Can someone give an example of how PV=nRT is used to convert Kp to Kc? Like, does R and T end up being contained in the answer?

Ana Pedreros
Posts: 62
Joined: Fri Sep 28, 2018 12:19 am

Re: Kc and Kp

Postby Ana Pedreros » Wed Jan 23, 2019 10:35 am

if looking for Kp with concentration given, n/v, can be substituted for the concentration and the pressure can be isolated in order to find the partial pressure of that gas and compete the Kp expression.if looking for Kc with pressure given, p, can be inserted in the equation and n/v can be isolated in order to find the concentration of that gas and compete the Kc expression. R and T will stay the same depending on the given conditions.

Brian Chang 2H
Posts: 65
Joined: Fri Sep 28, 2018 12:17 am

Re: Kc and Kp

Postby Brian Chang 2H » Wed Jan 23, 2019 11:38 am

Solids and liquids are not included in Kc and Kp.

Because (a) their pure and don't have concentrations, and (b) they don't have partial pressures.


Return to “Equilibrium Constants & Calculating Concentrations”

Who is online

Users browsing this forum: No registered users and 2 guests