## When to use C=5/2R or C=3/2R

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

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### When to use C=5/2R or C=3/2R

I was wondering when to use $C_{p}= \frac{5}{2}R$ for pressure and $C_{v}= \frac{3}{2}R$ for volume.

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### Re: When to use C=5/2R or C=3/2R

$C_{p}= \frac{5}{2}R$ and $C_{v}= \frac{3}{2}R$ are the heat capacities for monatomic ideal gases.

Taylor Pio 3H
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### Re: When to use C=5/2R or C=3/2R

What does the R stand for in this equation?

Stefanie Bui 1J
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### Re: When to use C=5/2R or C=3/2R

In this equation, R stands for the constant 8.3145 J*K-1*mol-1.

Joyce Zhang 2D
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### Re: When to use C=5/2R or C=3/2R

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### Re: When to use C=5/2R or C=3/2R

R is essentially the gas constant, which is 8.314 J * K^-1 * mol^-1. When we use this constant to find heat (q) with the equation q = m * c * delta t, we need to make sure the m is in moles because the unit of the constant is given per mole.

404982241
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### Re: When to use C=5/2R or C=3/2R

use the 5/2 when pressure is constant.
use 3/2 when volume is constant.

a great example is problem 8.31 in the 6th edition

Melody P 2B
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### Re: When to use C=5/2R or C=3/2R

404982241 wrote:use the 5/2 when pressure is constant.
use 3/2 when volume is constant.

a great example is problem 8.31 in the 6th edition

Would these only be used when working with an ideal gas?