Final answer:
Strontium, being a heavier alkaline earth metal than magnesium, would exhibit a more vigorous reaction with hydrochloric acid, producing hydrogen gas more rapidly and possibly with more heat.
Step-by-step explanation:
If strontium were to react with dilute hydrochloric acid instead of magnesium, one difference you might observe is a more vigorous reaction. Strontium is below magnesium in the reactivity series, indicating that strontium is a better reducing agent and more easily oxidized than magnesium. This can be inferred from the general trend that the heavier alkaline earth metals react more vigorously than the lighter ones. Therefore, when reacting with hydrochloric acid, strontium would produce hydrogen gas more rapidly and possibly increase the intensity of the reaction's exothermic character, as compared to magnesium. The reaction of strontium with dilute hydrochloric acid would yield strontium chloride and hydrogen gas:
Sr(s) + 2 HCl(aq) → SrCl₂(aq) + H₂(g)
This observation is aligned with the fact that the heavier alkaline earth metals, such as strontium, show more vigorous reactions with water and air at room temperature