Question

The aqueous solution of 'A' is alkaline due to

• A. the presence of $C{a}^{2+}$ ions
• B. the presence of $H_{3}B{O}_3$
• C. hydrolysis of $B_4{O}_7^{2-}$
• D. hydrolysis of $C{O}_3^{2-}$

Answer 1

The correct option is C hydrolysis of $B_4{O}_7^{2-}$

A is borax or sodium tetraborate $\left(N{a}_2{B}_4{O}_7.10H_{2}O\right)$.

One mole of A contains 10 moles of water of crystallization.

It is a white crystalline solid and is used in water softening. Its aqueous solution is alkaline due to the formation of sodium hydroxide upon hydrolysis of $N{a}_2{B}_4{O}_7$. The reaction is as follows:

$N{a}_2{B}_4{O}_7+7H_{2}O\rightleftharpoons 2NaOH+4H_{3}B{O}_3$