### When to use this equation

Posted:

**Mon Jan 13, 2020 2:13 pm**Hi, I was wondering when it is useful to use PV=nRT. Thanks!

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=123&t=56197

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Posted: **Mon Jan 13, 2020 2:13 pm**

Hi, I was wondering when it is useful to use PV=nRT. Thanks!

Posted: **Mon Jan 13, 2020 2:15 pm**

This equation has many uses, however, the one that Lavelle talked about in class is when you want to convert pressure to concentration as the following:

PV=nRT

P=(n/V)RT

P=concRT

Conc=P/RT

PV=nRT

P=(n/V)RT

P=concRT

Conc=P/RT

Posted: **Mon Jan 13, 2020 2:16 pm**

In the context of equilibrium, you use this equation to convert from pressure to concentration. So if you want to calculated K(p) and you are given concentration values, you can use PV=nRT to convert to partial pressure values for that reactant or product. The same applies for converting from pressure to concentration.

Posted: **Mon Jan 13, 2020 3:16 pm**

An example of when to use this function is if you are given pressure and need to find concentration. You can also use it to find the pressure if you are given concentration.

Posted: **Mon Jan 13, 2020 4:14 pm**

You would use this equation to convert between partial pressure and concentration. If you were asked specifically for Kp or Kc and given the opposite units, you would use this equation.

Posted: **Mon Jan 13, 2020 10:16 pm**

If you are given concentrations and asked to find Kp you can rearrange PV=nRT to solve for the partial pressures of the reactants and products. Conversely, if you were given partial pressures and asked to find Kc you could use the equation to convert the partial pressures into concentrations.

Posted: **Mon Jan 13, 2020 10:46 pm**

This equation is the ideal gas equation and should be used when you want to convert the concentration to pressure or vice versa.

Posted: **Mon Jan 13, 2020 11:31 pm**

PV= nRT is used for ideal gases only. if concentrations and Kp are given, this equation can be used to calculate the partial pressure of products and reactants and vice versa, if partial pressures are given, concentrations can be calculated using this method

Posted: **Mon Jan 13, 2020 11:37 pm**

This equation is super versatile. If you know a few variables and you are trying to figure out how to represent ideal gases differently, then, you can just rearrange the equation. For example, if you have the pressure of a gas, but want to know what the concentration of the gas is you just need to rearrange it to say: PV = nRT to P/RT = n/V.

n/V is concentration by the way (mols/volume)

This is really useful if you are trying to go from Kp to Kc.

n/V is concentration by the way (mols/volume)

This is really useful if you are trying to go from Kp to Kc.

Posted: **Tue Jan 14, 2020 12:32 pm**

I think you use PV=nRT when you're trying to switch between concentration and pressure of when trying to calculate the partial pressures.

Posted: **Fri Jan 17, 2020 4:22 pm**

One use is when a compound or reaction is not in the STP state (standard 1atm, 25C), and you need to find a certain value to plug into a stoichiometric equation. More for specialized cases...

Posted: **Sun Jan 19, 2020 7:41 pm**

PV= nRT is an overarching equation that can be manipulated to define a lot of different laws within chemistry, but I think the main thing to notice is the effect temperature has on pressure and volume, and the inversely proportional relationship between p and v

Posted: **Sun Jan 19, 2020 7:53 pm**

it's used to convert between pressure and concentration. When you are finding K for gasses that could. be in either pressure or concentration. You manipulate the equation to get a. simpler conversion. It starts as PV=nRT. then divide by V for P=(n/V)RT. And n/v is moles/Liter which is the definition of concentration. So, Pressure=concentration*RT which is then

Concentration=Pressure/RT

Concentration=Pressure/RT

Posted: **Sun Jan 19, 2020 9:33 pm**

PV=nRT is used to convert from a pressure of a gas back into a concentration

Posted: **Sun Jan 19, 2020 11:41 pm**

Are there any conditions where you can't use it? Like that could be a trick question?