# Internal energy equals to average kinectic energy ?

1. ### Outrageous

375
For ideal gas , can I assume Cv dT = nkT (3/2)
, thank you

2. ### Andrew Mason

6,856
No. Molar heat capacity, Cv = 3R/2 only for ideal monatomic gases. You are also mixing temperature change with temperature here.

Using molar heat capacity 3R/2 for a monatomic ideal gas:

$\int_{Ti}^{Tf} nC_vdT = \frac{3}{2}nR(T_f - T_i) = \frac{3}{2}nR\Delta T = \frac{3}{2}Nk\Delta T$

AM

3. ### Outrageous

375
Thanks for compact explanation.