Which metal listed below shows the strongest reaction when added to dilute hydrochloric acid?

The correct option is Magnesium.

Explanation:

When metals react with dilute hydrochloric acid, they produce a metal chloride salt and release hydrogen gas. The general reaction can be represented as:

$\text{Metal}+\text{Dilute Hydrochloric Acid}\to \text{Metal Chloride}+{\text{Hydrogen Gas}}_{\left(\text{g}\right)}$

The reactivity or vigor of this reaction depends on the position of the metal in the reactivity series. Metals that are higher up in the reactivity series lose electrons more readily (oxidize faster) and react more vigorously with acids.

Let's compare the position of the given metals in the reactivity series:

1. Magnesium ($\text{Mg}$): Highly reactive metal. It reacts rapidly with dilute hydrochloric acid, producing rapid bubbling (effervescence) of hydrogen gas and raising the temperature of the reaction mixture significantly (exothermic reaction).

$\text{Mg}+2\text{HCl}\to {\text{MgCl}}_2+{\text{H}}_2$

2. Zinc ($\text{Zn}$): Moderately reactive, less reactive than magnesium.

3. Iron ($\text{Fe}$): Slowly reacts with dilute hydrochloric acid compared to magnesium and zinc.

4. Copper ($\text{Cu}$): Lies below hydrogen in the reactivity series and does not react with dilute hydrochloric acid under normal conditions.

Order of reactivity with dilute acid among these metals:

$\text{Magnesium (Mg)}>\text{Zinc (Zn)}>\text{Iron (Fe)}>\text{Copper (Cu)}$

Therefore, Magnesium shows the strongest and most vigorous reaction with dilute hydrochloric acid.