(a) Determine the chemical formula of the product formed when the metallic element calcium combines with the nonmetallic element oxygen, O2. Write the balanced chemical equation for the reaction.
This is a pretty classic case of a combination reaction (2 reactants --> 1 product). Also, to predict the product, we recognize that a reaction between a metal and a nonmetal gives a salt. Ca forms the +2 ion, and oxygen forms a -2 ion, so the formula of the product is CaO. The balanced equation is
2Ca(s) + O2(g) --> 2CaO(s)
remember that oxygen exists as a diatomic gas, and ionic compounds tend to be solids!
(b) What products form when a compound containing C, H and O is completely combusted in air? Write a balanced chemical equation for the combustion of acetone, C3H6O(l), in air.
Combustion of a compound containing only C, H, and O involves the reaction between the compound and oxygen to form CO2(g) and H2O(l). This is a definition that you should know! So, for the combustion of acetone in air (the air is the source of the oxygen),
C3H6O(l) + 4O2(g) --> 3CO2(g) + 3H2O(l).