Partial Pressure vs. Concentration

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RRahimtoola1I
Posts: 102
Joined: Fri Aug 09, 2019 12:15 am

Partial Pressure vs. Concentration

Postby RRahimtoola1I » Sat Jan 25, 2020 11:55 am

It says on outline 1 that we have to know when to differentiate between using partial pressure and concentration for the equilibrium constant. How do we know which one to use when there are only gases but they don't give any other information like concentration or partial pressure?

Izzie Capra 2E
Posts: 103
Joined: Sat Sep 07, 2019 12:19 am

Re: Partial Pressure vs. Concentration

Postby Izzie Capra 2E » Sat Jan 25, 2020 1:17 pm

If it doesn't give a hint in the problem whether it is concentration (would give molarities) or partial pressure (atm or bar), you can use either as the ratio represents the same thing: products over reactants.

Sukanya Mohapatra 2G
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Joined: Sat Aug 17, 2019 12:18 am
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Re: Partial Pressure vs. Concentration

Postby Sukanya Mohapatra 2G » Sat Jan 25, 2020 4:32 pm

If not given additional info, either can be used since they represent the same quantity.

Diana Chavez-Carrillo 2L
Posts: 122
Joined: Fri Sep 28, 2018 12:18 am

Re: Partial Pressure vs. Concentration

Postby Diana Chavez-Carrillo 2L » Sat Jan 25, 2020 5:26 pm

Usually in the problem will you be given molarity or moles and this will hint that you need to use concentration (Kc) but if the problem gives you atm or barr then you will use the partial pressure (Kp). However, the question should be clear about which one you should be using from the given information.

san_2F
Posts: 118
Joined: Sat Jul 20, 2019 12:15 am

Re: Partial Pressure vs. Concentration

Postby san_2F » Sat Jan 25, 2020 6:19 pm

When they tell you to use partial pressures, you have to use the given information and plug into PV=nRT to find bars/atmospheres. When it's partial concentration, then you would just find moles over liters.

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

Re: Partial Pressure vs. Concentration

Postby Bryce Barbee » Sat Jan 25, 2020 6:22 pm

I believe in a problem it has to give you some sort of information that leads towards either using partial pressure or concentration. If it doesnt exactly specify Kc or P of something, but then gives you the moles of one of the final products, then you know that Kc should probably be used.


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