Past Paper Exam: Catalytic Converters
Formation · Removal Equation · Redox Analysis — Cambridge IGCSE Chemistry 0620
2CO(g) + 2NO(g) → 2CO₂(g) + N₂(g)
Formation of Oxides of Nitrogen
Explain how oxides of nitrogen are formed in a car engine.
Under normal atmospheric conditions, nitrogen and oxygen do not react. Suggest why they react inside a car engine.
State one oxide of nitrogen that is produced in a car engine.
Explain why the formation of nitrogen monoxide (NO) in car engines is an environmental problem.
Carbon monoxide (CO) is also produced in car engines. (a) State the condition required for CO to form rather than CO₂. (b) Explain why CO is dangerous to humans.
Removal Equation
Write the balanced symbol equation for the removal of carbon monoxide (CO) and nitrogen monoxide (NO) in a catalytic converter. Include state symbols.
Explain the role of the catalytic converter in the reaction: 2CO(g) + 2NO(g) → 2CO₂(g) + N₂(g).
In the reaction 2CO + 2NO → 2CO₂ + N₂, CO is converted to CO₂ and NO is converted to N₂. Describe why this conversion is important for the environment.
The metals used in catalytic converters include platinum (Pt) and rhodium (Rh). Suggest why these metals are used rather than iron (Fe).
The catalyst in a catalytic converter is in the form of a fine mesh or honeycomb structure. Explain the advantage of this shape.
Redox Analysis
In the reaction 2CO + 2NO → 2CO₂ + N₂, identify the oxidising agent. Explain your answer using oxidation numbers.
In the reaction 2CO + 2NO → 2CO₂ + N₂, identify the reducing agent. Explain your answer using oxidation numbers.
Define the terms 'oxidation' and 'reduction' in terms of (a) oxygen transfer and (b) electron transfer. Then state which applies to CO in the reaction 2CO + 2NO → 2CO₂ + N₂.
Calculate the oxidation number of nitrogen in: (a) NO, (b) N₂, (c) NO₂. Use your answers to explain which form of nitrogen has been most oxidised.
A student claims: 'In the catalytic converter reaction, N₂ is produced because nitrogen is being oxidised.' Evaluate this claim, using oxidation numbers to support your answer.
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