Partial molar entropies of components in an $A-B$ solution are given as:

$\frac{?}{\text{b}\text{a}\text{r}}(S{)}_i=S_i-Rln{x}_i,$ where $x_i$ is the mole fraction of component $i.$ Use $10$ and $20\frac{J}{m}$ole$-$

$K$ as standard entropies of A and $B$ respectively, to determine entropy change of $a$

process involving the addition of $1$ mole of $B$ into an $A-B$ solution with $x_B=0\mathrm{.}33$ initial

composition. Assume that addition is made to:

a$)3$ moles of solution,

b$)$ large quantity of solution.