For which one of the following reactions is the entropy change positive?

Direct conversion of $A$ to $B$ is difficult,so it is carried out by the path shown below. If $e.u.$ is the entropy unit,what will be $\Delta S_{(A \rightarrow B)}$?
Given:
$\Delta S_{(A \rightarrow C)} = 50 \ e.u.$
$\Delta S_{(C \rightarrow D)} = 30 \ e.u.$
$\Delta S_{(B \rightarrow D)} = 20 \ e.u.$

In which state does matter have the highest entropy?

The entropy change in the isothermal reversible expansion of $2 \, \text{moles}$ of an ideal gas from $10 \, L$ to $100 \, L$ at $300 \, K$ is $..... \, J \, K^{-1}$.

$A$ 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:

At $25\,^oC$ and $1\,atm$ pressure,mercury reacts with chlorine to form mercurous chloride: $2Hg + Cl_2 \to Hg_2Cl_2; \Delta H = -31.3\,kcal$. What is the entropy change of the reaction at $25\,^oC$?