Question

• Which among $\mathrm{Cu}$, $\mathrm{Fe}$, $\mathrm{Mg}$, $\mathrm{Na}$ and $\mathrm{Zn}$ does not react with a dilute $\mathrm{HCl}$ solution?

Answer 1

The metals that are present above the hydrogen in the reactivity series shows the reaction with dilute $\mathrm{HCl}$ solution.

Reactivity series of metals can be represented as

$\mathrm{K}>\mathrm{Na}>\mathrm{Ca}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Zn}>\mathrm{Fe}>\mathrm{Pb}>\mathrm{H}>\mathrm{Cu}>\mathrm{Hg}>\mathrm{Ag}>\mathrm{Au}$

• Copper does not react with a dilute $\mathrm{HCl}$ (hydrochloride) because in the reactivity series of metals, Copper $\left(\mathrm{Cu}\right)$ present below hydrogen.
• When $\left(\mathrm{Fe}\right)$ Iron reacts with dilute $\mathrm{HCl}$ solution then Ferrous chloride $\left({\mathrm{FeCl}}_2\right)$ and hydrogen $\left({\mathrm{H}}_2\right)$ gas is produced.

$\underset{\mathrm{Iron}}{\underbrace{\mathrm{Fe}\left(\mathrm{s}\right)}}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\underbrace{2\mathrm{HCl}(\mathrm{aq}.)}}\to \underset{\mathrm{Ferrous}\mathrm{chloride}}{\underbrace{{\mathrm{FeCl}}_2(\mathrm{aq}.)}}+\underset{\mathrm{Hydrogen}}{\underbrace{{\mathrm{H}}_2\left(\mathrm{g}\right)}}$

Here, Iron being more reactive than Hydrogen displaces Hydrogen from hydrochloric acid and forms Ferrous chloride and Hydrogen gas as a product.

• When magnesium $\left(\mathrm{Mg}\right)$ reacts with $\mathrm{HCl}$ solution then it forms a salt of magnesium chloride $\left({\mathrm{MgCl}}_2\right)$ and Hydrogen $\left({\mathrm{H}}_2\right)$ gas.

$\underset{\mathrm{Magnesium}}{\underbrace{\mathrm{Mg}\left(\mathrm{s}\right)}}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\underbrace{2\mathrm{HCl}(\mathrm{aq}.)}}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{\underbrace{{\mathrm{MgCl}}_2(\mathrm{aq}.)}}+\underset{\mathrm{Hydrogen}}{\underbrace{{\mathrm{H}}_2\left(\mathrm{g}\right)}}$

• When Sodium $\left(\mathrm{Na}\right)$ reacts with $\mathrm{HCl}$ solution then it forms Sodium chloride $\left(\mathrm{NaCl}\right)$ and hydrogen $\left({\mathrm{H}}_2\right)$ gas.

$\underset{\mathrm{Sodium}}{\underbrace{2\mathrm{Na}\left(\mathrm{s}\right)}}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\underbrace{2\mathrm{HCl}(\mathrm{aq}.)}}\to \underset{\mathrm{Sodium}\mathrm{chloride}}{\underbrace{2\mathrm{NaCl}}}+\underset{\mathrm{Hydrogen}}{\underbrace{{\mathrm{H}}_2\left(\mathrm{g}\right)}}$

• When Zinc $\left(\mathrm{Zn}\right)$ reacts with $\mathrm{HCl}$ solution then it gives Zinc chloride with evolution of Hydrogen $\left({\mathrm{H}}_2\right)$ gas.

$\underset{\mathrm{Zinc}}{\underbrace{\mathrm{Zn}}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\underbrace{2\mathrm{HCl}}(\mathrm{aq}.)}\to \underset{\mathrm{Zinc}\mathrm{chloride}}{\underbrace{{\mathrm{ZnCl}}_2(\mathrm{aq}.)}}+\underset{\mathrm{Hydrogen}}{\underbrace{{\mathrm{H}}_2\left(\mathrm{g}\right)}}$

Hence, from given elements, Copper$\left(\mathrm{Cu}\right)$ does not react with a dilute $\mathrm{HCl}$.