Two containers $C_1$ and $C_2$ of volumes $V$ and $4V$ respectively, hold the same ideal gas and are connected by a thin horizontal tube of negligible volume with a valve which is initially closed. The initial pressures of the gas in $C_1$ and $C_2$ are $p$ and $5p$, respectively. Heat baths are employed to maintain the temperatures in the containers at $300 \mathrm{K}$ and $400 \mathrm{K}$, respectively. The valve is now opened. Select the correct statement.

• A

  The gas will flow from the hot container to the cold one and the process is reversible.
• B

  The gas will flow from one container to the other till the number of moles in two containers are equal.
• C

  A long time after the valve is opened, the pressure in both the containers will be $3p$.
• Correct answer
  D

  A long time after the valve is opened, number of moles of gas in the hot container will be thrice that of the cold one.

Hence, the correct answer is option: 'D'.