Describe the extraction of lead from its ore and the purification of copper. Include relevant equations and explain the uses and drawbacks of lead compounds.

a)

i) The chief ore used to extract lead metal is Galena ($\text{PbS}$).

ii) At the purification stage, froth flotation is used to concentrate the ore by separating lead sulfide from gangue (impurities).

iii) The equation for the reaction that takes place when the ore is roasted in air is:

$$2\text{PbS(s)} + 3\text{O}_2\text{(g)} \to 2\text{PbO(s)} + 2\text{SO}_2\text{(g)}$$

iv)
S: Galena ($\text{PbS}$)
A: Lead(II) oxide ($\text{PbO}$)
K: Sulfur dioxide ($\text{SO}_2$)
C: Carbon dioxide ($\text{CO}_2$)
R: Crude Lead ($\text{Pb}$)

v) Iron is used in the blast furnace to remove sulfur impurities from lead sulfide:

$$\text{Fe(s)} + \text{PbS(s)} \to \text{FeS(l)} + \text{Pb(l)}$$

vi) Tetraethyl lead is being phased out because lead compounds are toxic and cause environmental pollution and health problems, particularly affecting the nervous system. It also poisons catalytic converters in vehicles.

b)

i) The method used to purify (concentrate) the copper ore is Froth flotation.

ii) In the reaction $\text{Cu}_2\text{S} + 2\text{Cu}_2\text{O} \to \text{Cu} + \text{SO}_2$, the reducing agent is Copper(I) sulfide ($\text{Cu}_2\text{S}$).