Zinc ore can contain zinc carbonate, ZnCO3\text{ZnCO}_3ZnCO3.
In the first stage of extraction, the zinc carbonate is decomposed by heating to form zinc oxide, ZnO\text{ZnO}ZnO, and carbon dioxide.
ZnCO3→ZnO+CO2 \text{ZnCO}_3 \rightarrow \text{ZnO} + \text{CO}_2 ZnCO3→ZnO+CO2When 125 g of zinc carbonate is decomposed completely, the total mass of the products formed is 125 g.
Give a reason why the mass of the reactant is always the same as the total mass of the products.
258 exam-style questions on Edexcel GCSE Chemistry Calculations involving masses. Each one has a worked solution and a mark scheme showing where the marks go.