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A certain amount of gas of volume \mathrm{V}$ at $27^{\circ} \mathrm{C} temperature and pressure 2 \times 10^{7} \mathrm{Nm}^{-2} expands isothermally until its volume gets doubled. Later it expands adiabatically until its volume gets redoubled. The final pressure of the gas will be (Use \gamma=1.5) :
 

Option: 1

3.536 \times 10^{5} \mathrm{~Pa}
 


Option: 2

3.536 \times 10^{6} \mathrm{~Pa}
 


Option: 3

1.25 \times 10^{6} \mathrm{~Pa}
 


Option: 4

1.25 \times 10^{5} \mathrm{~Pa}


Answers (1)

best_answer

Process \mathrm{A\rightarrow B} is isothermal process

\therefore \mathrm{P_{1}V=P_{2}\left ( 2v \right )}

     \mathrm{P_{2}=\frac{P_{1}}{2}}\rightarrow (1)

Process \mathrm{B\rightarrow C} is adiabatic process

\mathrm{P_2(2 v)^v=P_3(4 v)^v }

\mathrm{\frac{P_2}{P_3}=(2 )^{v}=(2 )^3/2 }

\mathrm{\frac{P_2}{P_3}=2 \sqrt{2}\: \: \rightarrow 2}

From eq.(1)&(2)

\mathrm{\frac{P_1}{2} =2 \sqrt{2} \: \: P_3 }

\mathrm{P_3 =\frac{P_1}{4 \sqrt{2}} }

       \mathrm{=\frac{2 \times 10^7}{4 \sqrt{2}} \\ }

\mathrm{P_3 =0.3536 \times 10^7}

The final pressure of the gas will be =3.536 \times 10^6\: \: \mathrm{pa}

Hence (2) is correct option.

 

Posted by

Gautam harsolia

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