Final answer:
The role of HCl when added to aluminum is to produce hydrogen gas (H2) and aluminum chloride (AlCl3), which helps to ensure that all aluminum has reacted and the surface is clean for accurate measurements.C is the correct.
Step-by-step explanation:
In the determination of a chemical formula, if 6 M HCl was added 30 minutes after the addition of the aluminum wire, the role of HCl at this step was to bring about the evolution of H2 gas.
When HCl is added to aluminum, a chemical reaction occurs where aluminum reacts with hydrochloric acid to form aluminum chloride (AlCl3) and hydrogen gas (H2).
This step is crucial in confirming that all aluminum is reacted, and it may also help to clean the surface of the aluminum, ensuring that accurate measurements can be made for the determination of the chemical formula.