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6. ⇒  (MHT CET 2023 9th May Morning Shift )

A jar ' P ' is filled with gas having pressure, volume and temperature P , V , T respectively. Another gas jar Q filled with a gas having pressure 2 P , volume V 4 and temperature 2   T . The ratio of the number of molecules in jar P to those in jar Q is

A. 1 : 1

B. 1 : 2

C. 2 : 1

D. 4 : 1

Correct Option is (D)

According to the ideal gas equation PV = Nk B T

For jar P , we have

PV = N 1 k B T ..... (i)

For jar Q, we have,

(2P) ( V 4 ) = N 2 k B ( 2   T )

PV = 4   N 2 k B T ..... (ii)

From equations (i) and (ii)

N 1 = 4 N 2 N 1 N 2 = 4 N 1 : N 2 = 4 : 1

7. ⇒  (MHT CET 2021 21th September Morning Shift )

A monoatomic gas at pressure ' P ' having volume ' V ' expands isothermally to a volume 2   V and then adiabatically to a volume 16   V . The final pressure of the gas is ( γ = 5 3 )

A. P 64

B. P 128

C. P 8

D. P 32

Correct Option is (A)

For isothermal process: P 1   V 1 = P 2   V 2

P 2 = P 1   V 1   V 2 = P 1 2 ( v 1 v 2 = 1 2 )

For adiabatic process : P 2   V 2 γ = P 3   V 3 γ

P 3 = P 2 ( V 2 V 3 ) γ = P 2 ( 2 V 1 V 3 ) γ = P 1 2 ( 1 8 ) 5 / 3 [ V 1 V 3 = 1 16 ] = P 1 2 1 32 = P 1 64