Which one of the following is the correct order of reactivity of Mg, Al, Zn and Fe with HCI? 

The correct answer is  Mg > Al > Zn > Fe.

Key PointsReactivity with HCI

• The reactivity of metals with hydrochloric acid (HCI) depends on their position in the reactivity series. The reactivity series is a list of metals arranged in order of decreasing reactivity.
• Magnesium (Mg) is more reactive than aluminum (Al), zinc (Zn), and iron (Fe) with HCI. This is because magnesium is higher up in the reactivity series.
• Aluminum (Al), though protected by an oxide layer, reacts with HCI once this layer is penetrated, making it more reactive than zinc and iron.
• Zinc (Zn) reacts with HCI to form zinc chloride (ZnCl₂) and hydrogen gas (H₂), but its reactivity is less than Mg and Al.
• Iron (Fe) is the least reactive among the given metals with HCI, reacting to form iron(II) chloride (FeCl₂) and hydrogen gas.

Additional Information

• The reactivity series is an essential concept in chemistry that predicts the outcome of reactions between metals and other substances. It helps in understanding which metal can displace another in a chemical reaction.
• Hydrochloric acid (HCI) is a strong acid that reacts with metals above hydrogen in the reactivity series to produce salt and hydrogen gas.
• The reaction of metals with HCI is an example of a single displacement reaction, where a more reactive metal displaces a less reactive metal from its compound.
• Understanding the reactivity of metals with acids like HCI is crucial in various applications, including metal extraction, corrosion prevention, and manufacturing of chemicals.
• The protective oxide layer on aluminum makes it less reactive initially, but once this layer is removed or penetrated, aluminum becomes quite reactive due to its relatively high position in the reactivity series.