Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Advanced 2019Paper 2
Exam
JEE Advanced
Year
2019
Paper
Paper 2
Subject
Physics
Chapter
Thermodynamics

JEE Advanced 2019 · Paper 2 · Physics · Thermodynamics

A mixture of ideal gas containing 5 moles of monatomic gas and 1...

A mixture of ideal gas containing 55 moles of monatomic gas and 11 mole of rigid diatomic gas is initially at pressure P0,{P}_{0}, volume V0{V}_{0} and temperature T0.{T}_{0} . If the gas mixture is adiabatically compressed to a volume V04\dfrac{{V}_{0}}{4}, then the correct statement(s) is/are,
(Given 21.2=2.3;23.2=9.2;R{2}^{1.2} = 2.3\text{;}{2}^{3.2} = 9.2\text{;}R is gas constant)

Options

  1. AThe final pressure of the gas mixture after compression is in between 9P09{P}_{0} and 10P010{P}_{0}.
  2. BThe average kinetic energy of the gas mixture after compression is in between 18RT018R{T}_{0} and 19RT019R{T}_{0}.
  3. CThe work ∣W∣\left|W\right| done during the process is 13RT013R{T}_{0}.
  4. DAdiabatic constant of the gas mixture is 1.61.6.

Correct answer

A. The final pressure of the gas mixture after compression is in between 9P09{P}_{0} and 10P010{P}_{0}.

Step-by-step solution

{Here,n1=5,CP1=52R,CV1=32Rn2=1,CP2=72R,CV2=52Rγmix=n1CP1+n2CP2n1CV1+n2CV2=85=1.6\begin{cases}\text{Here,}{n}_{1} = 5, & {C}_{{P}_{1}} = \dfrac{5}{2}R, & {C}_{{V}_{1}} = \dfrac{3}{2}R \\ {n}_{2} = 1, & {C}_{{P}_{2}} = \dfrac{7}{2}R, & {C}_{{V}_{2}} = \dfrac{5}{2}R\end{cases}{\gamma}_{mix} = \dfrac{{n}_{1}{C}_{{P}_{1}} + {n}_{2}{C}_{{P}_{2}}}{{n}_{1}{C}_{{V}_{1}} + {n}_{2}{C}_{{V}_{2}}} = \dfrac{8}{5} = 1.6
Work done, W=P1V1−P2V2γ−1,(Inadiabaticprocess)W = \dfrac{{P}_{1}{V}_{1} - {P}_{2}{V}_{2}}{\gamma - 1}, \left(Inadiabaticprocess\right)
Now, for adiabatic compression
P1V1r=P2V2r{P}_{1}{V}_{1}^{r} = {P}_{2}{V}_{2}^{r}
⇒P0V08/5=P2(V04)⇒ {P}_{0}{V}_{0}^{8 / 5} = {P}_{2}{\left(\dfrac{{V}_{0}}{4}\right)}^{8 / 5}<br/><br />⇒ {P}_{2} = 9.2{P}_{0} ⇒ \left(A\right)iscorrect.<br/>Now,is correct.<br />Now,W = \dfrac{{P}_{0}{V}_{0} - 9.2{P}_{0}\dfrac{{V}_{0}}{4}}{3 / 5} = - 13R{T}_{0} ⇒ (C)\left(C\right) is correct
∴∣W∣=13RT0∴ \left|W\right| = 13R{T}_{0}
Again T1V1γ−1=T2V2γ−1{T}_{1}{V}_{1}^{\gamma - 1} = {T}_{2}{V}_{2}^{\gamma - 1}
T2=T1(2)6/5=2.3T0{T}_{2} = {T}_{1}{\left(2\right)}^{6 / 5} = 2.3{T}_{0}
Average kinetic energy of gas mixture =nCVmixT2= n{C}_{{V}_{mix}}{T}_{2}
=23RT0⇒(B)= 23R{T}_{0} ⇒ \left(B\right) is incorrect
Practice Thermodynamics on Quantrex Academy →

More from Thermodynamics

A quasi-static cycle of a monoatomic ideal gas contains an isothermal process ( ab )… JEE Advanced 2026As shown in the figure, five Carnot engines, each with efficiency η and same number of… JEE Advanced 2026Ten moles of an ideal monoatomic gas, initially in state a at atmospheric pressure and… JEE Advanced 2026One mole of diatomic gas having rotational modes only is kept in a cylinder with a piston… JEE Main 2026Initial pressure and volume of a monoatomic ideal gas are P and V . The change in… JEE Main 2026A cylinder with adiabatic walls is closed at both ends and is divided into two… JEE Main 2026Two closed vessels of same volume are joined through a narrow tube and both vessels are… JEE Main 2026A certain gas is isothermally compressed to ((1)/(3))^ rd of its initial volume ( V_o = 3… JEE Main 2026 Full Thermodynamics list All JEE Advanced PYQs