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### Using Kc or Kp

Posted: Mon Jan 14, 2019 3:13 pm
How do we know when to use Kp or Kc? Sometimes it seems like you can use both?

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 3:13 pm
Use Kp when the reactants and products are gaseous, and use Kc when the reactants and products are aqueous.

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 3:17 pm
Kp should be used when the reactants and products deal with partial pressures and are gaseous while Kc should be used when the reactants and products are aqueous and deal with molarity.

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 3:31 pm
Kp is for partial pressure with units like atm, bar, torr, etc. Kc is for concentrations and will have mol/L for units

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 3:43 pm
Since Kc uses concentrations which are approximations, I know that we do not include mol/L units in our calculations. For Kp and partial pressures, do we leave out the units as well?

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 3:55 pm
both of them always work, you just have to see which information you are given to work with. If you are given moles and liters molarity can be found so Kc can be used but if pressures are given use Kp. Kp is also most commonly with gases

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 4:19 pm
Kp is used for gases, and Kc for concentrations. Sometimes Kc is used for gases as well, it depends on the question.

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 6:40 pm
Adam Vuilleumier 2K wrote:Since Kc uses concentrations which are approximations, I know that we do not include mol/L units in our calculations. For Kp and partial pressures, do we leave out the units as well?

Yes, I believe you can leave out units for both. Although when doing calculations using Partial Pressures, it may be helpful to leave them in.

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 6:41 pm
Rachel Yoo 1F wrote:Kp is for partial pressure with units like atm, bar, torr, etc. Kc is for concentrations and will have mol/L for units

Do you know how we would convert between these different units for partial pressure or if it would be necessary?

### Re: Using Kc or Kp

Posted: Mon Jan 14, 2019 6:48 pm
All of these are just units for partial pressures, in order to convert between them, you would just have to look up how each one relates to another for example 760 torr is equal to 1 atm so to go from atm to torr you just multiply by 760.

### Re: Using Kc or Kp

Posted: Wed Jan 16, 2019 12:13 am
Typically, Kp is used for when they give you partial pressures which means it will typically be used with problems that contain gases in the products or reactants.
Kc is used with concentration values and are typically used in problems with aqueous solutions. However, if a problem gives you the concentration of gasses, it's ok to use the Kc in that situation.

### Re: Using Kc or Kp

Posted: Wed Jan 16, 2019 1:05 am
You would use Kc when dealing with concentrations of substances and Kp when dealing with the partial pressures of gases

### Re: Using Kc or Kp

Posted: Wed Jan 16, 2019 11:09 am
Problems might also require you to convert between concentration and partial pressure so it is important to remember how to manipulate the ideal gas law to suit this purpose.

### Re: Using Kc or Kp

Posted: Wed Jan 16, 2019 12:58 pm
Kp is used when the substances are gaseous. But Kc can be used when the substances are gaseous or aqueous.