A black solid known to be an oxide of cobalt is analyzed to determine its chemical formula
CHEMISTRY · Multi-part · A Level · Chemistry · Amount of substance · Amount of substance
Problem
A black solid known to be an oxide of cobalt is analyzed to determine its chemical formula. A 1.500g sample of the oxide is completely reduced in a stream of hydrogen gas, producing metallic cobalt and 0.350g of liquid water. No other products form.
(a) Use the experimental data to determine the mass of oxygen present in the original oxide sample. Show your reasoning.
(b) Calculate the simplest whole-number ratio of cobalt atoms to oxygen atoms in the oxide and write its empirical formula.
(c) Determine the oxidation state of cobalt in this oxide. Explain how your answer follows from the empirical formula and ion charges.
(d) Provide the systematic name of the oxide, including the appropriate Roman numeral.