Bornite is an ore of copper that contains copper, iron, and sulfur.
The percentage composition by mass of bornite is:
Cu: 63.31%Fe: 11.17%S: 25.52% \text{Cu: } 63.31\% \quad \text{Fe: } 11.17\% \quad \text{S: } 25.52\% Cu: 63.31%Fe: 11.17%S: 25.52%Show, by calculation, that the empirical formula of bornite is Cu5FeS4\text{Cu}_5\text{FeS}_4Cu5FeS4.
Copper is obtained from bornite in a two-stage process.
Stage 1: Bornite is heated in air.
2Cu5FeS4+4O2→5Cu2S+2FeO+3SO2 2\text{Cu}_5\text{FeS}_4 + 4\text{O}_2 \rightarrow 5\text{Cu}_2\text{S} + 2\text{FeO} + 3\text{SO}_2 2Cu5FeS4+4O2→5Cu2S+2FeO+3SO2State why the sulfur in the reaction in Stage 1 is described as being oxidised.
In Stage 2, the copper(I) sulfide is separated and heated in air. It reacts with oxygen to form copper 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 methyl orange indicator can be used to show that the solution is acidic.
Give two observations that are made when a piece of calcium carbonate is added to the acidic solution.
