States of Matter · JEE Main previous year questions

2026 2 questions

1. Q572026 · 6 Apr 2026 · Shift 1

   One mole each of $\mathrm{He}$ and $\mathrm{A}(\mathrm{g})$ are taken in a $10\mathrm{L}$ closed flask and heated to $400\mathrm{K}$ to establish the following equilibrium. $\mathrm{A}(\mathrm{g})\rightleftharpoons \mathrm{B}(\mathrm{g})$ ${\mathrm{K}}_{\mathrm{c}}$ for this reaction at $400\mathrm{K}$ is $4.0$. The partial pressures (in $\mathrm{atm}$) of $\mathrm{He}$ and $\mathrm{B}(\mathrm{g})$ are respectively (at equilibrium) (Assume $\mathrm{He}$, $\mathrm{A}(\mathrm{g})$ and $\mathrm{B}(\mathrm{g})$ behave as ideal gases) (Given : $\mathrm{R}=0.082\mathrm{L}\mathrm{atm}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$)

   1. A.3.28, 2.624
   2. B.2.624, 3.28
   3. C.3.28, 0.656
   4. D.0.656, 6.56
   Show answer

   Answer: A

2. Q522026 · 28 Jan 2026 · Shift 1

   $20.0\mathrm{d}{\mathrm{m}}^3$ of an ideal gas ' X ' at $600\mathrm{K}$ and $0.5\mathrm{MPa}$ undergoes isothermal reversible expansion until pressure of the gas is $0.2\mathrm{MPa}$ . Which of the following option is correct? (Given: $\log 2=0.3010$ and $\log 5=0.6989$ )

   1. A.$w=-9.1\mathrm{kJ}$, $\Delta U=0$, $\Delta H=0$, $q=9.1\mathrm{kJ}$
   2. B.$w=9.1\mathrm{J}$, $\Delta U=9.1\mathrm{J}$, $\Delta H=0$; $q=0$
   3. C.$w=-3.9\mathrm{kJ}$, $\Delta U=0$, $\Delta H=0$; $q=3.9\mathrm{kJ}$
   4. D.$w=+4.1\mathrm{kJ}$, $\Delta U=0$, $\Delta H=0$; $q=-4.1\mathrm{kJ}$
   Show answer

   Answer: A