Question

You are given the following materials:

1. Marble chips
2. Dilute Hydrochloric acid
3. Zinc granules

Identify the type of reaction when marble chips and Zinc granules are added separately to acid taken in two tubes. Write chemical equations in each case.

Answer 1

i) Double displacement reaction:

The chemical reaction in which one of the components of both reactants is exchanged to form the products is known as a double displacement reaction.

For example:

The reaction between Barium chloride$\left({\mathrm{BaCl}}_2\right)$ and Sodium sulphate solution$\left({\mathrm{Na}}_2{\mathrm{SO}}_4\right)$ is a Double displacement reaction.

${\mathrm{BaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{Na}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)\to {\mathrm{BaSO}}_4\left(\mathrm{s}\right)+2\mathrm{NaCl}\left(\mathrm{aq}\right)$

When Marble chips$\left({\mathrm{CaCO}}_3\right)$ react with dilute Hydrochloric acid$\left(\mathrm{HCl}\right)$, it forms Calcium chloride$\left({\mathrm{CaCl}}_2\right)$ and Carbonic acid$\left({\mathrm{H}}_2{\mathrm{CO}}_3\right)$. The acid changes to Carbon dioxide$\left({\mathrm{CO}}_2\right)$ and Water$\left({\mathrm{H}}_2\mathrm{O}\right)$.

Hence it is a double displacement reaction.

The chemical equation is written as,

${\mathbf{CaCO}}_{\mathbf{3}\mathbf{}}\mathbf{\left(}\mathbf{s}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}\mathbf{2}\mathbf{HCl}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}{\mathbf{CaCl}}_{\mathbf{2}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}{\mathbf{CO}}_{\mathbf{2}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}\mathbf{+}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{O}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}$

ii) Displacement reaction:

A reaction in which one of the elements takes the place of another element is known as a Displacement reaction.

For example:

The Reaction of Iron$\left(\mathrm{Fe}\right)$ with Copper sulphate$\left({\mathrm{CuSO}}_4\right)$ solution is a displacement reaction where Iron takes the place of Copper.

$\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{FeSO}}_4\left(\mathrm{aq}\right)$

When Zinc granules are reacted with Hydrochloric acid$\left(\mathrm{HCl}\right)$ it forms Zinc chloride$\left({\mathrm{ZnCl}}_2\right)$ and Hydrogen gas.

Hence, it is a Displacement reaction.

The chemical equation is written as,

$\mathbf{Zn}\mathbf{\left(}\mathbf{s}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{2}\mathbf{HCl}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{\to }\mathbf{}{\mathbf{ZnCl}}_{\mathbf{2}}\mathbf{\left(}\mathbf{aq}\mathbf{\right)}\mathbf{}\mathbf{+}\mathbf{}{\mathbf{H}}_{\mathbf{2}}\mathbf{\left(}\mathbf{g}\mathbf{\right)}$