Carrollite is a sulfide mineral containing copper, cobalt, and sulfur.
The percentage composition by mass of carrollite is:
Cu: 20.52%Co: 38.13%S: 41.35% \text{Cu: } 20.52\% \quad \text{Co: } 38.13\% \quad \text{S: } 41.35\% Cu: 20.52%Co: 38.13%S: 41.35%Show, by calculation, that the empirical formula of carrollite is CuCo2S4\text{CuCo}_2\text{S}_4CuCo2S4. [Relative atomic masses: Ar(Cu)=63.5A_r(\text{Cu}) = 63.5Ar(Cu)=63.5, Ar(Co)=59A_r(\text{Co}) = 59Ar(Co)=59, Ar(S)=32A_r(\text{S}) = 32Ar(S)=32]
Cobalt and copper are obtained from carrollite in a multi-stage process.
Stage 1: Carrollite is heated in air.
2CuCo2S4+3O2→Cu2S+4CoS+3SO2 2\text{CuCo}_2\text{S}_4 + 3\text{O}_2 \rightarrow \text{Cu}_2\text{S} + 4\text{CoS} + 3\text{SO}_2 2CuCo2S4+3O2→Cu2S+4CoS+3SO2State why the sulfur in the reaction in Stage 1 is described as being oxidised.
In Stage 2, the cobalt(II) sulfide (CoS\text{CoS}CoS) is separated and heated in air. It reacts with oxygen to form cobalt(II) oxide (CoO\text{CoO}CoO) and sulfur dioxide. Write a balanced chemical equation for the reaction that occurs in Stage 2.
Sulfur dioxide dissolves in water to form an acidic solution.
Identify the ion that causes this solution to be acidic.
State how blue litmus paper can be used to show that the solution is acidic.
Give two observations that are made when a piece of magnesium carbonate is added to the acidic solution.
