Gas Evolution in Acid-Carbonate Reaction

Steps:

• CO₂ gas produced escapes the flask, reducing total mass as reaction proceeds.
• Graph slope (volume vs. time) steepens initially then flattens, showing decreasing reaction rate due to reactant depletion.
• Volume levels off after four minutes, indicating no further gas production and reaction completion.
• All three statements match these observations from the apparatus and graph.

Why A is correct:

• In closed-system mass loss experiments, escaping products like CO₂ cause continuous decrease until reaction ends, per conservation of mass.

Why the others are wrong:

• B omits statement 3, but graph plateau confirms finish at four minutes.
• C omits statement 2, but decreasing slope proves rate slows over time.
• D omits statement 1, but gas escape directly causes mass reduction.

Final answer: A