Question

Is Calcium Hydroxide an Acid or an Alkali?

Answer 1

Bases are ionic compounds that produce negative hydroxide (OH-) ions when dissolved in water.

• A "strong base" is a compound that has the ability to remove a proton from a very weak acid.
• They completely dissociate into its ions when in water.
• The strong bases are known as Alkali.

Acids: An acid is a hydrogen-containing substance capable of donating a proton (hydrogen ion) to another substance.

• Acidic substances are usually recognized by their sour taste.
• It can turn blue litmus paper red.

Calcium hydroxide Ca(OH)₂ is a Alkali (strong base) and it becomes 100% ionized into calcium ions and hydroxide ions.

• Because when dissolved in water, it dissociates into two ions (Ca²⁺ and 2OH^–).
• The presence of OH^- ions in an aqueous solution of Ca(OH)₂ makes it alkaline in nature.
• Since Ca(OH)₂ dissociates into Ca²⁺ and 2OH^- and the OH^- ion accepts a proton (H⁺) to form water.
• $\underset{(\mathrm{Calcium}\mathrm{hydroxide})}{\mathrm{Ca}{\left(\mathrm{OH}\right)}_2}+\left(\mathrm{aq}\right)\to \underset{\left(\mathrm{Calcium}\right)}{{\mathrm{Ca}}^{2+}\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Hydroxide}\right)}{2{\mathrm{OH}}^{–}\left(\mathrm{aq}\right)}$
• The pH value of calcium hydroxide is (11−12.5) and pKb value is 1.37 (First OH⁻) and 2.43 (second OH⁻).