Which one of the following is the correct reactivity order of metals reacting with dilute HCl?

The reactivity of metals with dilute hydrochloric acid (HCl) is determined by the rate of hydrogen gas evolution and the exothermic nature of the reaction. According to experimental observations, magnesium (Mg) reacts most vigorously, showing the fastest rate of bubble formation and the highest temperature increase [1]. While aluminium (Al) may initially appear less reactive due to a protective oxide layer, once this layer is removed, it reacts more quickly than zinc (Zn) and iron (Fe). The standard reactivity series places these metals in descending order of reactivity as Magnesium > Aluminium > Zinc > Iron [2]. Consequently, the correct sequence representing the decreasing order of reactivity with dilute HCl is Mg > Al > Zn > Fe, making option 1 the correct choice.

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > Activity 3.11 > p. 44
2. [2] Science , class X (NCERT 2025 ed.) > Chapter 3: Metals and Non-metals > 3.2.5 The Reactivity Series > p. 45