Q.An aqueous solution of borax is :

Borax hydrolyses in water to give boric acid and sodium hydroxide; since $NaOH$ is a strong base and $H_3BO_3$ is a weak acid, the resulting solution is basic (alkaline).

Borax dissociates and hydrolyses approximately as $Na_2B_4O_7 + 7H_2O \rightarrow 2NaOH + 4H_3BO_3$. Because sodium hydroxide is a strong, fully-ionised base while boric acid is a weak acid, the strong base dominates the resulting solution's equilibrium, giving it a basic (pH > 7) character — this is why borax is …