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

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:
[itex]\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[/itex]
AM