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Cv vs. Cp

Posted: Sun Jan 21, 2018 5:50 pm
by Miranda 1J
Can someone please explain when we use Cv and when we use Cp and how we would know which one to use? Also, what's the difference between DH= nCpDT and DH= gCspDT? Does it matter which one we use?

Thanks!

Re: Cv vs. Cp

Posted: Sun Jan 21, 2018 5:58 pm
by SPandya1F
Use Cv when there's constant volume. This is the specific heat when there's constant volume.
Use Cp when there's constant pressure. This is the specific heat when there's constant pressure.

Re: Cv vs. Cp

Posted: Sun Jan 21, 2018 5:59 pm
by Clarisse Wikstrom 1H
Cv is the molar heat capacity of a gas @ CONSTANT VOLUME, whereas Cp is the molar heat capacity of a gas at CONSTANT PRESSURE. In one example (#31), you would use it when doing q=mCdeltaT if you're given an ideal gas but no molar heat capacity. The Cp and Cv for ideal gases can be found on Lavelle's equation sheet on his website.

Re: Cv vs. Cp

Posted: Sun Jan 21, 2018 6:13 pm
by Julian Krzysiak 2K
Cp is the heat capacity for something at a constant pressure, and would be equal to
Cv is the heat capacity for something at a constant volume, and would be equal to
You'll know when to use a particular heat capacity because they'll specify in the problem the conditions of the reaction, or you'll have to infer the conditions, for example, when there is an open container, it will have to be at a constant pressure of 1atm.
You usually use these equations when dealing with anything in calculating how much heat was given off, the change in temperature, or any variation in dealing with


is the specific heat capacity for something at a constant pressure in terms of moles
is the specific heat capacity for something at a constant pressure in terms of grams
So you'll have to use either one depending in which units they give the amount to you, or if given enough information, you could convert grams into moles, vice versa, and then use which equation you want.

Re: Cv vs. Cp

Posted: Sun Jan 21, 2018 10:30 pm
by AlyssaPeckham1A
Also to solve for the values of Cvm and Cpm you can use the equations Cvm=3/2*R and Cpm=5/2*R for the molar heat capacity.

Re: Cv vs. Cp

Posted: Mon Jan 22, 2018 2:54 pm
by Katelyn 2E
Will we have to know the Cvm and Cpm values for the test?

Re: Cv vs. Cp

Posted: Thu Jan 25, 2018 1:06 pm
by Lucia H 2L
They are listed on the formula sheet!
Ideal gas, Cp = (5/2)R
Ideal gas, Cv = (3/2)R
Both are constant because heat capacity for gases isn't dependent on temp or volume.

Re: Cv vs. Cp  [ENDORSED]

Posted: Mon Jan 29, 2018 1:20 am
by Justin Bui 2L
We would also be told the conditions of the problem and then we would know which one to use, Cp or Cv, based off of that.

Re: Cv vs. Cp

Posted: Mon Feb 05, 2018 6:34 pm
by Guadalupe T 1E
The problem usually states when there is constant pressure/volume

Re: Cv vs. Cp

Posted: Mon Feb 12, 2018 7:03 pm
by Warda Sahib 2J
Cv-is when there's constant volume and Cp-is when there's constant pressure.

Re: Cv vs. Cp

Posted: Mon Feb 12, 2018 9:02 pm
by Abby Ellstrom 1I
Cv is when the volume is constant and Cp is when the pressure is constant.

Re: Cv vs. Cp

Posted: Wed Jan 30, 2019 4:41 pm
by Kenan Kherallah 2C
Whats R?

Re: Cv vs. Cp

Posted: Thu Jan 31, 2019 10:18 am
by Brian Chang 2H
Cv is for constant volume.
Cp is for constant pressure.

Re: Cv vs. Cp

Posted: Thu Jan 31, 2019 10:49 am
by Jeannine 1I
Kenan Kherallah 2C wrote:Whats R?


I believe R refers to the universal gas constant!