When two gases are mixed,the entropy $......$

Which one of the following involves a decrease in entropy?

The $\Delta S$ for the vaporisation of $1 \ mol$ of water is $88.3 \ J/mol \ K$. The value of $\Delta S$ for the condensation of $1 \ mol$ of vapour will be.......$ J/mol \ K$

$A$ heat engine is operating between $500 \ K$ and $400 \ K$. If the engine absorbs $100 \ J$ of heat,which of the following is an impossible amount of heat rejected by the engine (in $J$)?

The change of entropy $(dS)$ is defined as

Which of the following processes takes place with a decrease of entropy?