A-LevelChemistryGroup 29701/12 · May/June 2015 · Q141 Mark

Compound X releases carbon dioxide gas and forms a white solid, Y, when it is heated. Neither X nor Y are soluble in water. Compound Y is used as a refractory kiln lining. What is compound X?

ACaCO₃

BCaO

CMgCO₃

DMgO

✓ Correct answer

C: MgCO₃

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