Given: Two monoatomic gases initially have the same P, V, and T. Gas A is compressed isothermally to 8V, and gas B is compressed adiabatically to 8V.
Find: The ratio of final pressure of gas B to final pressure of gas A.
For the isothermal compression of gas A:
PV=constant
So,
PA′⋅8V=PV
Hence,
PA′=8PFor the adiabatic compression of gas B:
PVγ=constant
For a monoatomic gas,
γ=35
Therefore,
PB′(8V)35=PV35
So,
PB′=P⋅835Now compute the required ratio:
PA′PB′=8PP⋅835=832=4Therefore, the ratio of final pressure of gas B to that of gas A is 4. Hence, the correct option is C.
Note: The source options list shows 81 as option C, while the working gives the value 4. The solution explicitly marks option C, but by the actual calculation the defensible answer corresponds to the value 4.