Question

Alkali which dissociates only partially in aqueous solution is

• A. Lithium hydroxide
• B. Calcium hydroxide
• C. Potassium hydroxide
• D. Sodium hydroxide​

Answer 1

The correct option is A

Lithium hydroxide

• A strong alkali dissociates completely in an aqueous solution whereas a weak alkali dissociates partially in an aqueous solution.
• Calcium hydroxide dissociates completely in an aqueous solution.

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\to {\mathrm{Ca}}^{2+}+2{\mathrm{OH}}^{-}$

• Potassium hydroxide also dissociates completely in an aqueous solution.

$\mathrm{KOH}\to {\mathrm{K}}^{+}+{\mathrm{OH}}^{-}$

• Sodium hydroxide dissociates completely in an aqueous solution as

$\mathrm{NaOH}\to {\mathrm{Na}}^{+}+{\mathrm{OH}}^{-}$

• Lithium hydroxide dissociates in the aqueous solution as:

$\mathrm{LiOH}\rightleftharpoons {\mathrm{Li}}^{+}+{\mathrm{OH}}^{-}$

• This is because the lithium ion, being smaller in size gets extensively solvated. Thus, in lithium hydroxide, due to solvation, dissociation occurs only partially.

Hence, the correct option is (A).