Give one observation the student could make during Step 4 which shows that the copper carbonate is in excess.
How to approach this question
Step 4 involves adding copper carbonate until it is in excess. This means all the sulfuric acid has reacted. What would you see if the solid you are adding is no longer reacting?
Full Answer
Solid/powder remains at the bottom of the beaker / no more fizzing occurs.
When copper carbonate is added to sulfuric acid, it reacts and dissolves, producing carbon dioxide gas (fizzing). Once all the sulfuric acid has been used up, the reaction stops. If more copper carbonate is added, it will not react and will simply sink to the bottom of the beaker as an unreacted solid. Therefore, seeing solid powder at the bottom or observing that the fizzing has stopped are clear indications that the copper carbonate is in excess.
Common mistakes
✗ Stating the solution changes colour - this happens during the reaction, not specifically when excess is reached.
✗ Just saying "the reaction stops" without a specific observation.
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