Question

You are given a chemical reaction in which zinc reacts with dilute hydrochloric acid to form zinc chloride and hydrogen gas.

Zinc + Hydrochloric acid (dilute) $$\rightarrow$$ Zinc chloride + Hydrogen

Design and perform an experiment to test the hypothesis that mass is conserved during the chemical reaction. You may use a set-up different from the one shown in Activity 9.2.

Answer 1

1. Take 20 mL of dilute hydrochloric acid (HCl) in a conical flask and 0.65 g of zinc (Zn) in a small inner vial.
2. Place the vial inside the flask without mixing the reactants. Seal the flask with a balloon to prevent gas from escaping.
3. Weigh the entire apparatus using a digital balance and record the initial mass.
4. Tilt the flask to mix zinc with dilute HCl without opening the apparatus. The reaction produces hydrogen gas, which inflates the balloon.
5. Weigh the entire apparatus again and record the final mass.

Chemical Reaction:

\[ \mathrm{Zn + 2HCl \rightarrow ZnCl_2 + H_2\uparrow} \]

Observation:

The total mass before and after the reaction remains the same within experimental error.

Conclusion:

The experiment verifies the Law of Conservation of Mass, which states that mass is neither created nor destroyed during a chemical reaction.

Precaution:

Perform the experiment under teacher supervision, away from flames, as hydrogen gas is highly flammable.