Students use data gathered from the formation of copper oxides in order to write empirical formulas for these copper oxides.
Students form copper oxide using two methods. In the first, they heat dry copper powder until it combines with oxygen in the air; they compare the mass of copper to that of copper oxide and determine the ratio of copper to oxygen in the compound. In the second, they use an aqueous solution of copper (II) sulfate combined with sodium hydroxide to produce a copper hydroxide precipitate. This is heated until a decomposition reaction yields water vapor and copper oxide; students calculate the molar quantity of copper oxide produced and determine its empirical formula.