Question

one mole of helium is adiabatically expanded from its initial state(Pi, Vi, Ti) to it's final state (Pf, VF, Tf). The decrease in the internal energy associated with this expansion is equal to

pls help me in this ​

Answer 1

Answer:

∆ U = n C (Ti - Tf)

Explanation:

The enthalpy equation can be written

∆ Q = ∆U + ∆W

In case of any adiabatic process, ∆Q is zero, which means that

∆ U =  - ∆W

Also the work done in adiabatic is positive, so change in enthalpy would be negative

∆ U = negative

∆ U = n C (∆ T)

∆ U = n C (Ti - Tf)

The negative sign would indicate decrease in energy

Answer 2

Answer:

Cv(Ti-Tf)

Explanation:

dQ=dU+dW

Since its an adiabatic process dQ=0

Therefore, 0= dU+dW

                  dU= (-ve) dW

          Its mentioned that gas expands = dW=+ve

         therefore the final internal energy decreases

     Answer :  Cv(Ti-Tf)