Chemistry 9701 · AS & A Level · Nitrogen and sulfur

Nitrogen and sulfur — practice question

Sulfuric acid is a significant chemical that has many uses. It is produced by the Contact process, and the first step is the conversion of sulfur or a sulfide ore, such as galena, $\text{PbS}$, into sulfur dioxide, $\text{SO}_2$.
(a(i))[2]

Write an equation for the reaction of galena with oxygen to produce sulfur dioxide and lead(II) oxide.

(a(ii))[2]

Identify the oxidation number changes that occur during this reaction.

(b(i))[3]

State the temperature normally selected for this conversion and explain it using reaction rates and Le Chatelier’s principle.

(b(ii))[3]

State and explain the pressure conditions that would produce the best rate and best yield of sulfur trioxide. Explain why these conditions are not actually used.

(c(i))[1]

Explain why the sulfur trioxide is not dissolved directly in water to produce sulfuric acid.

(c(ii))[2]

Write equations for sulfur trioxide reacting with sulfuric acid and for the later reaction with water.

(d)[2]

Explain why sulfur dioxide is added to certain foods and wines.

(e(i))[1]

How many moles of $\text{SO}_2$ are in $50.0\,\text{cm}^3$ of wine?

(e(ii))[1]

How many moles of $\text{SO}_2$ are in $1\,\text{dm}^3$ of wine?

(e(iii))[1]

How many milligrams, $\text{mg}$, of $\text{SO}_2$ are in $1\,\text{dm}^3$ of wine? Give your answer to three significant figures. $(1\,\text{g} = 1000\,\text{mg})$

Worked solution & mark scheme

This 18-mark question has a full step-by-step worked solution and mark scheme. One marking point: $2PbS + 3O_2 \rightarrow 2PbO + 2SO_2$

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