During a metallurgical investigation into catalyst preparation, a sample of 2.407 g of an oxide of cobalt is completely reduced by heating in a stream of hydrogen gas. The reaction produces cobalt metal and 0.720 g of water.
What is the empirical formula of this cobalt oxide?
[Ar A_r\,Ar values: H=1.0\text{H} = 1.0H=1.0, O=16.0\text{O} = 16.0O=16.0, Co=58.9\text{Co} = 58.9Co=58.9]
CoO\text{CoO}CoO
Co2O3\text{Co}_2\text{O}_3Co2O3
Co3O4\text{Co}_3\text{O}_4Co3O4
CoO2\text{CoO}_2CoO2
