Achemical formula written above or below the yield sign indicates:
a. that a gas is formed.
b. that the substance is used as a catalyst.
c. that heat must be supplied.
d. a reversible reaction.

Reacting masses1 calcium carbonate breaks down on heating to produce calcium oxide and carbondioxide gas.caco3 + cao + co2a student heats 15 g of calcium carbonate strongly in a crucible.relative atomic masses (a): ca = 40, c = 12, o = 16.calculate the mass of calcium oxide produced by this reaction.(5 marks)