Question

The properties of alkalis are due to the presence of ______ ions.
(A) positive
(B) negative
(C) hydroxyl
(D) both B and C

Answer 1

Think about the properties of alkalis. Alkalis are bases so, think which property differentiates alkalis and bases.

Complete step by step solution:
- Alkalis are bases.
- Alkalis are compounds which contain hydroxyl ions, $O{{H}^{-}}$ in them.
- When an alkali is dissolved in water, it dissolves in water and dissociates to form hydroxyl ions.
- Any species which are capable of releasing hydroxyl ions in water are known as Alkalis.
- In the periodic table, we have the first group named as alkali metals. This implies the first group contains metals which form hydroxides. These hydroxides dissociate in water to give hydroxyl ions.
- For example, potassium hydroxide, KOH and sodium chloride, NaOH which are alkalis. KOH and NaOH dissociate in water to form ${{K}^{+}}$ and $N{{a}^{+}}$ respectively and hydroxyl ions.
- All alkalis are bases but all bases are not alkalis.
- Bases are the species which either donate hydroxyl ions or donate electrons or accept protons.
- For example, ammonia is a base but not an alkali and NaOH is an alkali as well as a base.
- Therefore, the properties of alkalis are due to the presence of hydroxyl ions.

- So, the correct answer is option (C).

Note: Remember all alkalis are bases but all bases are not alkalis. An alkali is a species containing hydroxyl ion or hydroxide group in it. A base is a species which contains hydroxyl ions or can donate electrons or accept protons.