Question

Write the main difference between an acid and a base. With the help of suitable examples explain the term Neutralisation and the formation of -

1. Acidic
2. Basic
3. Neutral salts

Answer 1

Difference between acids and bases:

Acids	Bases
A substance which releases one or more H+ ions in an aqueous solution.	A substance which is capable of releasing one or more OH- ions in an aqueous solution.
Its strength is based on the concentration of H+ ions.	Its strength is based on the concentration of ${\mathrm{OH}}^{-}$ ions.
The pH value is less than 7	The pH value is more than 7.
It turns the blue litmus into red color.	It turns the red litmus into blue color.
It is sour in taste.	It is bitter in taste.
Phenolphthalein remains colorless in acids.	Phenolphthalein becomes pink in bases.
Methyl orange changes to red colour in acids	Methyl orange changes to yellow colour in bases.

Neutralisation:

The reaction between acid and base present in an aqueous solution to form salt and water is known as Neutralisation.

$\mathrm{Acid}+\mathrm{Base}\to \mathrm{Salt}+\mathrm{Water}$

For example:

When Hydrochloric acid $\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ reacts with Sodium hydroxide$\mathbf{\left(}\mathbf{NaOH}\mathbf{\right)}$ it produces Sodium chloride salt$\mathbf{\left(}\mathbf{NaCl}\mathbf{\right)}$ and Water.

$\mathrm{HCl}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)$

i) Formation of acidic salts:

The acidic salts are formed from the Neutralisation reaction between a strong acid and weak base.

For Example:

When the strong acid Hydrochloric acid$\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ reacts with weak base Ammonia$\mathbf{\left(}{\mathbf{NH}}_{\mathbf{3}}\mathbf{\right)}$, it forms acidic salt Ammonium chloride$\mathbf{\left(}{\mathbf{NH}}_{\mathbf{4}}\mathbf{Cl}\mathbf{\right)}$

${\mathrm{NH}}_3\left(\mathrm{aq}\right)+\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)$

ii) Formation of basic salts:

The basic salts are formed from the Neutralisation reaction between a strong base and weak acid.

For example:

When strong base Sodium hydroxide$\mathbf{\left(}\mathbf{NaOH}\mathbf{\right)}$ reacts with weak acid Acetic acid$\mathbf{\left(}{\mathbf{CH}}_{\mathbf{3}}\mathbf{COOH}\mathbf{\right)}$, it forms basic salt Sodium acetate$\mathbf{\left(}{\mathbf{CH}}_{\mathbf{3}}\mathbf{COONa}\mathbf{\right)}$.

$\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{aq}\right)\to {\mathrm{CH}}_3\mathrm{COONa}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)$

iii) Formation of neutral salts:

The neutral salts are formed from the Neutralisation reaction between a strong acid and a strong base.

For example:

When the strong acid Hydrochloric acid$\mathbf{\left(}\mathbf{HCl}\mathbf{\right)}$ and strong base Sodium hydroxide$\mathbf{\left(}\mathbf{NaOH}\mathbf{\right)}$, it forms neutral salts.

$\mathrm{HCl}\left(\mathrm{aq}\right)+\mathrm{NaOH}\left(\mathrm{aq}\right)\to \mathrm{NaCl}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{aq}\right)$