What happens to the total entropy of the system and surroundings during a spontaneous irreversible process?

Entropy is maximum in case of

$A$ container is divided into two compartments by a removable partition as shown below:
In the first compartment,$n_{1}$ moles of ideal gas $He$ is present in a volume $V_{1}$. In the second compartment,$n_{2}$ moles of ideal gas $Ne$ is present in a volume $V_{2}$. The temperature and pressure in both the compartments are $T$ and $p$,respectively. Assuming $R$ is the gas constant,the total change in entropy upon removing the partition when the gases mix irreversibly is:

The unit of entropy is

What is the change in entropy when an ideal gas expands into a vacuum?

Which of the following reactions has $\Delta S > 0$?