The entire process can be represented as : (P0,V0)suddenly−−−−−−−→CompressedStep−I(P1,V06)slowly−−−−−−−→CompressedStep−II(P2,V036)
A diathermic wall means the gas is capable of exchanging heat with the surroundings.
During step - I, when the gas is suddenly compressed, the process is adibatic as there is no chance for the heat to escape from the system.
Thus, using the equation of state of an adiabatic process in terms of P and V, we get
P0Vγ0=P1Vγ1
From the data given in the question,
P0Vγ0=P1(V06)γ
⇒P1=(6γ)P0 .....(1)
During step - II, when the gas is slowly compressed, the gas can exchange heat with the surroundings through the diathermic wall, thus the process will be isothermal in nature.
Using equation of state of an isothermal process,
P1V1=P2V2,
We get, P2×(V036)=P1×(V06)
⇒P2=6P1
But from (1), we know that P1=(6γ)P0
∴P2=6×(6γ)P0
⇒P2=(6γ+1)P0
Thus, n=6