a$)500$ ml to prepare a buffer solution with pH $14\mathrm{.}25.$ How many grams of sodium benzoate should be added to $0\mathrm{.}100$ M benzoic acid solution. Ka$($C$6$H$5$COOH$)-6\mathrm{.}28$x$10^-8($C:$12$ g$/$mol$.$ Na:$23$ g$/$mol;$0$:$16$g$/$mol$)$

b$)$ When $0\mathrm{.}0100$ mol NaOH is added to this solution

c$)$ Calculate the change in pH when $0\mathrm{.}0100$ mol HCl is add