Science — AI-generated practice question

Fizzing will occur more vigorously in the test tube containing HCl (hydrochloric acid).

HCl is a strong acid that completely dissociates in water, producing a high concentration of H⁺ ions:
$$\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_2 + \text{H}_2\uparrow$$

CH₃COOH (acetic acid) is a weak acid that only partially dissociates, producing fewer H⁺ ions at the same concentration.

Since the rate of reaction between magnesium and the acid depends on the concentration of H⁺ ions, HCl provides more H⁺ ions, causing faster and more vigorous evolution of hydrogen gas (fizzing).

---

The key concept here is strong acid vs. weak acid. Examiners expect students to:

1. Correctly identify HCl as the test tube with more vigorous fizzing.
2. Link the reason to degree of dissociation → H⁺ ion concentration → rate of reaction.
3. Write the balanced equation for at least one reaction (HCl with Mg is sufficient).

Do not just say "HCl is stronger" without explaining why that leads to more fizzing — the H⁺ ion concentration argument is what earns the marks.