Pyrargyrite is an ore of silver that contains silver, antimony, and sulfur.
The percentage composition by mass of pyrargyrite is:
Ag: 59.78%Sb: 22.51%S: 17.71% \text{Ag: } 59.78\% \quad \text{Sb: } 22.51\% \quad \text{S: } 17.71\% Ag: 59.78%Sb: 22.51%S: 17.71%Show, by calculation, that the empirical formula of pyrargyrite is Ag3SbS3\text{Ag}_3\text{SbS}_3Ag3SbS3.
Silver is obtained from pyrargyrite in a two-stage process.
Stage 1: Pyrargyrite is heated in air.
4Ag3SbS3+9O2→6Ag2S+2Sb2O3+6SO2 4\text{Ag}_3\text{SbS}_3 + 9\text{O}_2 \rightarrow 6\text{Ag}_2\text{S} + 2\text{Sb}_2\text{O}_3 + 6\text{SO}_2 4Ag3SbS3+9O2→6Ag2S+2Sb2O3+6SO2State why the sulfur in the reaction in Stage 1 is described as being oxidised.
In Stage 2, the silver sulfide is separated and heated in air. It reacts with oxygen to form silver 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 litmus solution 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.
80 exam-style questions on Edexcel IGCSE Chemistry Chemical formulae, equations and calculations. Each one has a worked solution and a mark scheme showing where the marks go.