Question

Which of the following will produce an alkaline solution when dissolved in water?
(i) $\text{Borax}$
(ii) $N{H}_{4}Cl$
(iii) $N{a}_{2}C{O}_3$
(iv) $N{H}_{4}N{O}_3$

• A. (i), (iii)
• B. (i), (ii) and (iv)
• C. (i), (ii) and (iii)
• D. (i) only

Answer 1

The correct option is A (i), (iii)

(i) Borax, $N{a}_2{B}_4{O}_7.10H_{2}O$ when dissolved in water produces $NaB(OH{)}_4$ and $H_{3}B{O}_3$ having a pH of about nine.
(ii) $N{H}_{4}Cl$ is the salt of a strong acid ($HCl$) and a weak base ($N{H}_{4}OH$). So, its aqueous solution is acidic in nature.
(iii) $N{a}_{2}C{O}_3$, when dissolved in water gives $NaOH$ and $H_{2}C{O}_3$. Due to a higher concentration of $O{H}^{-}$, the solution becomes alkaline.
(iv) $N{H}_{4}N{O}_3$ is the salt of a strong acid ($HN{O}_3$) and a weak base ($N{H}_{4}OH$). So, its aqueous solution is acidic.