Question

Define each of the following with one example:

(b) Weak acids

Answer 1

Acids:

• An acid is a substance in which the only positive ion is hydrogen.
• It can be replaced by a metal or basic radical.

Weak acids:

• An acid that dissociates partially or to a little extent when dissolved in water producing a low concentration of ${\mathrm{H}}^{+}$ or ${\mathrm{H}}_3{\mathrm{O}}^{+}$ ions is called a weak acid.
• For example, Carbonic acid $\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$.
• Their solutions contain both ions and undissociated molecules of the solute.
• The dissociation equation of Carbonic acid is as follows:
  $$\begin{gathered} {\mathrm{H}}_2{\mathrm{CO}}_3\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{HCO}}_3^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right) \\ {\mathrm{HCO}}_3^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{CO}}_3^{2-}\left(\mathrm{aq}\right)+{\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right) \end{gathered}$$