## Kc vs Kp

$PV=nRT$

connie 2C
Posts: 106
Joined: Thu Jul 11, 2019 12:17 am

### Kc vs Kp

when a chemical equation is written and all the reactants and products are gases, do you use Kp rather than Kc? in what cases do you use Kc rather than Kp?

ayushibanerjee06
Posts: 177
Joined: Thu Jul 11, 2019 12:16 am
Been upvoted: 1 time

### Re: Kc vs Kp

You use Kp when all the products and reactants are gases and the question includes units like bar/atm/pa. You use Kc when the products and reactants are given in moles or molarity, even if the products and reactants are gases. If the question asks for Kp and the question only gives you information about moles/molarity, use the ideal gas law and solve for pressure (P= (n/v)RT). Vice versa if they ask for Kc and they only give you information about pressure. Also, keep in mind there are different gas constants, so use the one that fits the units you have. Hope this helps.

Rida Ismail 2E
Posts: 139
Joined: Sat Sep 07, 2019 12:16 am

### Re: Kc vs Kp

Kc is used when you have the molarity of a solution. Kp is always used with gases.

Justin Quan 4I
Posts: 104
Joined: Sat Sep 14, 2019 12:17 am

### Re: Kc vs Kp

To add on, you use Kp when the reactants and products are gases. If your reaction has gases and/or aqueous substances, then use Kc. However, if you're still having trouble deciding, you should check the units to ensure you're using the right K, for example Barr (pressure) vs M (concentration).

Minh Ngo 4G
Posts: 137
Joined: Thu Jul 25, 2019 12:17 am

### Re: Kc vs Kp

If all the reactants are gas then use Kp. You can calculate Kc for gas too but they would have to explicitly tell you so

Ying Yan 1F
Posts: 101
Joined: Fri Aug 02, 2019 12:16 am

### Re: Kc vs Kp

It really depends what information the problems gives you. If the concentrations of the reactants and products are given, then you you Kc, on the other hand, if the pressure of the reactants and products are given then you use Kp.

ValerieChavarin 4F
Posts: 99
Joined: Wed Sep 18, 2019 12:18 am

### Re: Kc vs Kp

It depends on what asked and given. If you are calculating molar concentration then you would use Kc.

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

### Re: Kc vs Kp

You can use kp when the reactants and products are gases and the partial pressures of the gases are given rather than their concentrations

vanessas0123
Posts: 100
Joined: Wed Sep 11, 2019 12:17 am

### Re: Kc vs Kp

You calculate Kc if given concentration. Kp if partial pressures are given.

Posts: 50
Joined: Tue Nov 05, 2019 12:18 am

### Re: Kc vs Kp

You use Kc when you are given a concentration, while Kp is used when given partial pressures. However, you can use Kp to find Kc if needed.

Angela Prince 1J
Posts: 102
Joined: Sat Aug 24, 2019 12:17 am

### Re: Kc vs Kp

connie 2C wrote:when a chemical equation is written and all the reactants and products are gases, do you use Kp rather than Kc? in what cases do you use Kc rather than Kp?

You can use whatever is convenient when they're all gases. You cannot use KP if it's not a gas.

Zoe Gleason 4F
Posts: 51
Joined: Tue Jul 23, 2019 12:15 am

### Re: Kc vs Kp

Kp can be used when all the concentrations are in pressure, and Kc when they are concentrations. Pressure can be converted to concentration by using PV=nRT (and vice versa), but all the species must be in the gas phase to use Kp.

Leila_4G
Posts: 114
Joined: Sat Sep 14, 2019 12:17 am

### Re: Kc vs Kp

From what I understand, pressures can be used with Kc or Kp but concentrations can only be used with Kc. Right?

Gurmukhi Bevli 4G
Posts: 49
Joined: Wed Nov 14, 2018 12:20 am

### Re: Kc vs Kp

Kc is used when you're dealing with molar concentrations, or when all the substances in your reaction are aqueous. Kp is used for partial pressures, or when the substances in your reaction are all gases.

annikaying
Posts: 94
Joined: Sat Sep 14, 2019 12:16 am

### Re: Kc vs Kp

kp is used when dealing with gases and is usually given with units like atm or bar. kc is for molar concentrations and will be given as aqueous solutions.

905373636
Posts: 62
Joined: Thu Aug 01, 2019 12:15 am

### Re: Kc vs Kp

The difference here just has to do with units used, though Kp will include all gases yes.

WYacob_2C
Posts: 102
Joined: Sat Jul 20, 2019 12:16 am

### Re: Kc vs Kp

Kp is used when dealing with partial pressures, so typically gases. Kc is used when dealing with concentration, so aqueous species.

Emil Velasco 1H
Posts: 96
Joined: Wed Nov 21, 2018 12:19 am

### Re: Kc vs Kp

You use Kp unless it specifically asks for Kc

William Francis 2E
Posts: 101
Joined: Wed Sep 18, 2019 12:20 am

### Re: Kc vs Kp

Kp should be used with gases since you're dealing with partial pressures rather than concentrations.

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

### Re: Kc vs Kp

It all depends on the information given. You would use Kp when the partial pressures are given, but you use Kc when the concentration or moles or grams are given even when the reactants and products are gases.

Kylie Lim 4G
Posts: 110
Joined: Sat Aug 17, 2019 12:15 am

### Re: Kc vs Kp

For a reaction that is entirely gasses, Kp can be used if the pressure is given. Kc can be used for gasses as well if the pressure is converted to concentration, or concentration is given initially.

Megan Cao 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:18 am

### Re: Kc vs Kp

kp is used for gases since they deal with Pressure. kc is used for questions involving molarity, generally solutions, however you can find the concentration of gases too. you would have to use the ideal gas law, pv=nrt

Caroline Zepecki
Posts: 101
Joined: Fri Aug 09, 2019 12:16 am

### Re: Kc vs Kp

Kp is for partial pressures of gasses, Kc on the other hand is the equilibrium constants

Hannah Pham
Posts: 104
Joined: Fri Aug 09, 2019 12:17 am

### Re: Kc vs Kp

If the reaction consists of all gases then you would use Kp. Kc can be used for gases as well if the gases are given in concentration rather than pressure.

105311039
Posts: 107
Joined: Fri Aug 02, 2019 12:16 am

### Re: Kc vs Kp

Kp is used with partial pressures like gases such as ATM. But Kc is used when you have things like aq concentrations.

Anushka Chauhan2B
Posts: 51
Joined: Sat Aug 24, 2019 12:16 am

### Re: Kc vs Kp

Kp should be used for gases since you are dealing with partial pressures

Jesse Anderson-Ramirez 3I
Posts: 54
Joined: Thu Sep 26, 2019 12:18 am

### Re: Kc vs Kp

Kp is for gases and uses partial pressure. Kc uses concentrations.

Astrid Lunde 1I
Posts: 103
Joined: Sat Sep 07, 2019 12:16 am

### Re: Kc vs Kp

Kp is when you deal with partial pressure so it is used for gasses. Use Kc when you see aq.

KaleenaJezycki_1I
Posts: 127
Joined: Sat Aug 17, 2019 12:18 am
Been upvoted: 2 times

### Re: Kc vs Kp

connie 2C wrote:when a chemical equation is written and all the reactants and products are gases, do you use Kp rather than Kc? in what cases do you use Kc rather than Kp?

Kc should be used normally, but the question will clarify if it wants molar concentrations or partial pressures. Therefore pay attention to the question, also Kc will be in units of mol.L-1 and Kp will be in bar or atm.

205405339
Posts: 77
Joined: Thu Jul 11, 2019 12:16 am

### Re: Kc vs Kp

You use Kp because K=kp for all cases. Kc=K when certain conditions are met

MTanikella_1K
Posts: 110
Joined: Sat Jul 20, 2019 12:16 am

### Re: Kc vs Kp

Kp is used when all products and reactants in the equation are gases. Another indication to use Kp is if the question uses units like bar or atm. Kc is used when the molarity of the products and reactants is given, even though the products and reactants involved in the reaction are gases.

Aarushi Solanki 4F
Posts: 107
Joined: Sat Jul 20, 2019 12:17 am

### Re: Kc vs Kp

Kp is used when the quantity of gases are given in context of pressure. Kc is used when the molarity of solutions or gases are given.

Rosa Munoz 2E
Posts: 105
Joined: Wed Sep 18, 2019 12:21 am

### Re: Kc vs Kp

Kc is concentration Kp is partial pressure.

Hannah Romeo 1J
Posts: 58
Joined: Thu Jul 11, 2019 12:16 am

### Re: Kc vs Kp

You use Kc when you have concentrations in molarity snd use Kp when you have partial pressures.

Maika Ngoie 1B
Posts: 97
Joined: Fri Aug 02, 2019 12:16 am

### Re: Kc vs Kp

In that instance, you would use Kp, Kc is used for molar concentration.

William Chan 1D
Posts: 102
Joined: Sat Sep 14, 2019 12:15 am

### Re: Kc vs Kp

If the reactants and products are given in units of pressure (bars, atmospheres, etc.), then use kp. If reactants and products are given in units of concentration (mol/L), then use kc.

Jasmine W 1K
Posts: 49
Joined: Sat Sep 07, 2019 12:18 am

### Re: Kc vs Kp

Kp is used with gases and Kc is used when you are dealing with concentrations.

Ryan Yoon 1L
Posts: 55
Joined: Mon Jul 01, 2019 12:15 am

### Re: Kc vs Kp

Kc deals with concentrations and Kp deals with atm and torr.

Alan Cornejo 1a
Posts: 98
Joined: Fri Aug 30, 2019 12:15 am

### Re: Kc vs Kp

Kp is used in the event that you products and reactants all exists in a gas phase. Therefore we use the partial pressures of the gases and make sure the units we use as a result also take that into inclusion. For Kc we use that when we are trying to determine concentration rather than the pressure.

Bryce Barbee
Posts: 103
Joined: Wed Sep 18, 2019 12:20 am

### Re: Kc vs Kp

It depends on if the give you pressures or concentrations. I am pretty sure that you can use both if its a gas though.

Catherine Daye 1L
Posts: 104
Joined: Wed Sep 11, 2019 12:16 am

### Re: Kc vs Kp

You use Kp for gases if you use partial pressure for gases. You can also change pressure to concentration using PV=nRT and in that case, you would use Kc since you’re now using concentrations.

Gerald Bernal1I
Posts: 102
Joined: Thu Jul 11, 2019 12:16 am

### Re: Kc vs Kp

Kc is used if you are given concentrations and Kp is used when you are given partial pressures.

805422680
Posts: 103
Joined: Sat Sep 14, 2019 12:16 am

### Re: Kc vs Kp

Kc is used when you are given concentrations, and Kp is used when you are given partial pressures of gases. When Kp is given, the products and reactants are both gases. When Kc is given, the products and reactants can consist of gases or aqueous solutions

briannam_1F
Posts: 35
Joined: Wed Sep 18, 2019 12:18 am

### Re: Kc vs Kp

Kc is used when molarity is given. When it comes to gas you only use Kp when given partial pressures or asked to convert to partial pressures.