Question

Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. Amount and concentration taken for both the acids are the same. In which test tube will the fizzing occur more vigorously and why?

Answer 1

Part 1: Reaction of metal with an acid

• When an acid reacts with metal, it will lead to the formation of salt and hydrogen gas.
• $\mathrm{Metal}+\mathrm{Acid}\to \mathrm{Salt}+{\mathrm{H}}_2$
• The production of hydrogen gas is responsible for fizzing.

Part 2: Identifying the test tube which is fizzing more vigorously

Test Tube A: Magnesium Ribbon + Hydrochloric acid

• Hydrochloric acid is a strong acid that reacts with magnesium leading to the formation of magnesium chloride and hydrogen gas.
• The balanced chemical reaction can be represented as:

$\underset{\mathrm{Magnesium}}{\mathrm{Mg}}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}}\to \underset{\mathrm{Magnesium}\mathrm{chloride}}{{\mathrm{MgCl}}_2}+\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2}$

Test Tube B: Magnesium Ribbon + Acetic acid

• Acetic acid is a weak acid that reacts with magnesium leading to the formation of magnesium acetate and hydrogen gas.
• The balanced chemical reaction can be represented as:

$\underset{\mathrm{Magnesium}}{\mathrm{Mg}}+\underset{\mathrm{Acetic}\mathrm{acid}}{2{\mathrm{CH}}_3\mathrm{COOH}}\to \underset{\mathrm{Magnesium}\mathrm{acetate}}{\mathrm{Mg}{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2}+\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2}$

Hence, Hydrochloric acid is a strong acid, a lot of hydrogen gas is liberated from test tube A. As a result, more fizzing occurs in test tube A.