Question

Show the dissociation of the following compounds on dissolving in water, with the help of chemical equation and write whether the proportion of dissociation is small or large.
Hydrochloric acid, sodium chloride, potassium hydroxide, ammonia, acetic acid, magnesium chloride, copper sulphate.

Answer 1

Hint: To answer this question we should know what dissociation means. To determine the proportion of dissociation we should know the strength of the given compounds. High strength means the large dissociation of the compound. So, the proportion of dissociation will be high.

 Complete step by step answer:
The decomposition of a compound on dissolution is known as dissociation.
Hydrochloric acid is a strong acid. It dissociates completely in water to give hydronium ions and chloride ions.
The chemical equation of dissociation of hydrogen chloride is shown as follows:
${\text{HCl}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{{\text{H}}_{\text{3}}}{{\text{O}}^{{\text{ + }}\,}}{\text{ + }}\,{\text{C}}{{\text{l}}^ - }$
Hydrochloric acid dissociates completely, so the proportion of dissociation is large.

Sodium chloride is a salt. Salt contains ions that remain in ionized form. Sodium chloride dissociates completely in water to give sodium ions and chloride ions.
The chemical equation of dissociation of sodium chloride is shown as follows:
${\text{NaCl}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{\text{N}}{{\text{a}}^{{\text{ + }}\,}}{\text{(aq) + }}\,{\text{C}}{{\text{l}}^ - }{\text{(aq)}}$
Here, no reaction takes place only the sodium chloride dissociates. Sodium chloride dissociates completely, so the proportion of dissociation is large.

Potassium hydroxide is a strong base. Potassium hydroxide dissociates completely in water to give potassium ions and hydroxide ions.
The chemical equation of dissociation of potassium hydroxide is shown as follows:
${\text{KOH}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{{\text{K}}^{{\text{ + }}\,}}{\text{(aq) + }}\,{\text{O}}{{\text{H}}^ - }{\text{(aq)}}$
Here, no reaction takes place only the potassium hydroxide dissociates. Potassium hydroxide dissociates completely and produces a small number of hydroxide ions so the proportion of dissociation is small.

Ammonia is a weak base. Ammonia dissociates readily in water to give ammonium ions and hydroxide ions.
The chemical equation of dissociation of ammonia is shown as follows:
${\text{N}}{{\text{H}}_3}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to \,{\text{NH}}_4^ + {\text{ + }}\,{\text{O}}{{\text{H}}^ - }$
Ammonia reacts rapidly but produces a small number of hydroxide ions so the proportion of dissociation is small.

Acetic acid is a weak acid. Acetic acid dissociates in water to give the acetate ion and hydronium ion.
The chemical equation of dissociation of acetic acid is shown as follows:
${\text{C}}{{\text{H}}_3}{\text{COOH}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to {\text{C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^ - }{\text{ + }}\,{{\text{H}}_3}{{\text{O}}^ + }$
Acetic acid dissociates and produces a large number of hydronium ions so the proportion of dissociation is large.

Magnesium chloride dissociates and produces a large number of ions so the proportion of dissociation is large.
The chemical equation of dissociation of magnesium chloride is shown as follows:
${\text{MgC}}{{\text{l}}_{\text{2}}}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to {\text{M}}{{\text{g}}^{2 + }}{\text{(aq) + }}\,{\text{2}}\,\,{\text{C}}{{\text{l}}^ - }{\text{(aq)}}$
Magnesium chloride dissociates and produces a large number of ions so the proportion of dissociation is large.

Copper sulphate dissociates in water to give copper ions and sulphate ions.
The chemical equation of dissociation of copper sulphate is shown as follows:
${\text{CuS}}{{\text{O}}_4}\,{\text{ + }}\,{{\text{H}}_{\text{2}}}{\text{O}}\, \to {\text{C}}{{\text{u}}^{2 + }}{\text{(aq) + }}\,{\text{SO}}_4^{2 - }{\text{(aq)}}$
Copper sulphate dissociates and produces a large number of ions so the proportion of dissociation is large.

Note: Proportion of dissociation tells the dissociated amount. Strong acid, base and salt dissociate completely in water, so their proportion of dissociation is high. Water is a polar compound, so remains in ionize as proton and hydroxide ions. The compound which produces hydroxide ion causes the increase in hydroxide ion so the reaction goes in the backward direction. So, the proportion of dissociation is small for the hydroxide-ion producing compound.