## Concentration or Partial Pressure

$PV=nRT$

Shuyi Yu 1B
Posts: 60
Joined: Fri Sep 28, 2018 12:16 am

### Concentration or Partial Pressure

When do we use concentration to find the equilibrium constant and when do we use partial pressure to find equilibrium constant? Will the question ask for one of the two specifically?

monikac4k
Posts: 56
Joined: Fri Sep 28, 2018 12:25 am

### Re: Concentration or Partial Pressure

I am pretty sure that the problem will specify whether we need to calculate kc or kp. It should be made explicit for us.

harshitasarambale4I
Posts: 58
Joined: Fri Sep 28, 2018 12:26 am

### Re: Concentration or Partial Pressure

Yes, the question should specify. However, it is important to remember that if you are given moles of gas, you have to convert it to units of pressure using the PV=nRT equation.

Riley Dean 2D
Posts: 60
Joined: Fri Sep 28, 2018 12:15 am

### Re: Concentration or Partial Pressure

You can also tell by looking at if the equation is made up of all gases or if its made up of aqueous solutions, gases meaning use Kp and aqueous solutions meaning use Kc

Bruce Chen 2H
Posts: 60
Joined: Fri Sep 28, 2018 12:26 am

### Re: Concentration or Partial Pressure

By looking at the reactants and products and seeing what you have is the first step in solving the problem. The question will usually say what to use to calculate the K value.

Nina Do 4L
Posts: 61
Joined: Fri Sep 28, 2018 12:27 am

### Re: Concentration or Partial Pressure

If the reactants are all gaseous, you can use their partial pressures to find Kp. If they are a mixture of gases and aqueous solutions, then your best bet is to use Kc. Very similar equations, just Kp uses the partial pressure of the gases while Kc uses the concentrations. Hope that helps!

Athena L 1B
Posts: 59
Joined: Fri Sep 28, 2018 12:18 am

### Re: Concentration or Partial Pressure

You still calculate them the same way right?

Nghi Nguyen 2L
Posts: 61
Joined: Fri Sep 28, 2018 12:18 am

### Re: Concentration or Partial Pressure

you can calculate them the same way but the question will specify which to use by giving you a value

Max Hayama 4K
Posts: 63
Joined: Fri Sep 28, 2018 12:16 am

### Re: Concentration or Partial Pressure

If the question gives you partial pressures, normally in atm, then you will be calculating for Kp. If you are given the concentrations of the reactants or products then you will most likely be calculating for Kc. Of course, make sure to determine what the question is asking for.

Simmi Diwanji 2B
Posts: 32
Joined: Fri Sep 28, 2018 12:20 am

### Re: Concentration or Partial Pressure

It should specify, but you should do what makes sense. Aqueous solutions will have concentrations so you should find Kc while gases will probably have partial pressures (but it could also be concentration) so you should find Kp.

Jennifer Lathrop 1F
Posts: 71
Joined: Sat Dec 02, 2017 3:00 am

### Re: Concentration or Partial Pressure

When do you know if you should use to the equation to convert it or not?

Emily Kennedy 4L
Posts: 57
Joined: Fri Sep 28, 2018 12:25 am
Been upvoted: 1 time

### Re: Concentration or Partial Pressure

if you are given one value in a concentration and one in partial pressure you should use the equation to get them all in the same units

shouse1f
Posts: 63
Joined: Fri Sep 28, 2018 12:18 am

### Re: Concentration or Partial Pressure

Shuyi Yu 1B wrote:When do we use concentration to find the equilibrium constant and when do we use partial pressure to find equilibrium constant? Will the question ask for one of the two specifically?

the question should normally specify which you should use

Yiting_Gong_4L
Posts: 69
Joined: Fri Sep 28, 2018 12:25 am

### Re: Concentration or Partial Pressure

the question will tell you when to use Kc or Kp