When heated, zinc carbonate decomposes to form zinc oxide and carbon dioxide gas - Edexcel - GCSE Chemistry - Question 1 - 2021 - Paper 1

To confirm the decomposition of zinc carbonate is complete, the student should take the following steps:

1. Heat the Sample Further: The student can continue to heat the sample for a longer period of time to ensure that all zinc carbonate has fully decomposed. Keeping the heat at a constant level is crucial.

2. Measure Mass Again: After further heating, the student should measure the mass of the crucible with the contents once more.

3. Compare Masses: Compare the mass obtained after additional heating with the previous mass measurements. If the mass remains constant after subsequent heatings, it indicates that no further decomposition is occurring.

4. Observation: The student can also observe for any fizzing or gas escape; the absence of any reaction or fizzing indicates that the decomposition has likely completed.

5. Remove Samples if Necessary: If confusion arises, the student can remove a portion of the product and test it chemically (for example, using acid to check for carbon dioxide) to further confirm the presence of zinc oxide.