when to solve for specific vs. molar heat capacity

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Joanna Pham - 2D
Posts: 113
Joined: Fri Apr 06, 2018 11:04 am

when to solve for specific vs. molar heat capacity

Postby Joanna Pham - 2D » Thu Feb 07, 2019 1:23 pm

How do you know to calculate for specific or molar capacity if it's not specified in the question? For instance, for 8.31, the question asks for us to "calculate the heat released by 5.025 g of Kr(g) at 0.400 atm as it cools from 97.6 C to 25.0 C at (a) constant pressure and (b) constant volume. Assume that krypton behaves as an ideal gas." The question does not specify which to solve for, so how would I know if I am supposed to solve for specific heat capacity or molar heat capacity?

Thanks!

Tyra Nguyen 4H
Posts: 74
Joined: Fri Sep 28, 2018 12:25 am

Re: when to solve for specific vs. molar heat capacity

Postby Tyra Nguyen 4H » Thu Feb 07, 2019 1:37 pm

I believe that we will typically use heat the specific heat capacity. Unless we deal specifically with moles, I would not use molar heat capacity to make it easier in terms of units.

The formula to calculate the heat released is q = m*C*T. To calculate the heat capacity, C, for a constant pressure, the formula is 5/2R, which equals 20.8 (J/mol)/(degree C).

mbaker4E
Posts: 69
Joined: Fri Sep 28, 2018 12:26 am

Re: when to solve for specific vs. molar heat capacity

Postby mbaker4E » Thu Feb 07, 2019 1:37 pm

Specific heat capacity is the heat requires to raise 1 gram of a substance by 1 degree Celsius/Kelvin, whereas molar heat capacity is the heat required to raise 1 mole of substance by 1 degree Celsius/Kelvin. Look and see if the problem gives you grams or moles, and go from there.


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