Reducing climate change and acid-rain emissions
Match each required strategy with the emission or removal process it addresses.
Exam scope and assessment notes
Core and Extended · Chemistry 0971, 2026–2028. The detailed greenhouse mechanism, catalytic-converter equation and photosynthesis symbol equation are taught in separate Extended lessons. Cambridge states that IGCSE 0971 has the same subject content as IGCSE 0620, with 9–1 grading. This StudyForA pathway maps the 2026–2028 syllabus only. This 9–1 graded qualification is available only in a limited number of administrative zones. Confirm that your centre can enter you for this code and exam series with Cambridge International. Cambridge has published a separate syllabus for 2029. StudyForA has not reconciled that version yet; this page supports exams in 2026, 2027 and 2028 only.
Before you begin
- Recall pollutant sources and effects.
- Distinguish an acidic oxide from a basic oxide.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which required pollutant is directly reduced by lowering fuel sulfur?
What you will learn
- State and explain the required climate-change strategies.
- Connect catalytic converters, low-sulfur fuels and calcium oxide treatment with acid-rain emission reduction.
Explain the climate strategy through the carbon or methane link
Planting trees increases the potential for carbon dioxide uptake through photosynthesis as trees grow. Reducing livestock farming can reduce methane emissions associated with animals' digestion and their waste. Decreasing fossil-fuel use reduces the carbon-containing fuel combustion contribution to CO₂ emissions. Each explanation connects a named strategy with a source or removal process rather than claiming an immediate reversal of all warming.
Increasing use of hydrogen and renewable energy such as wind and solar can reduce reliance on fossil-fuel combustion. Hydrogen contains no carbon, so the hydrogen reaction itself does not produce CO₂; how the hydrogen and energy are produced still matters for a full impact comparison. Wind and solar electricity likewise avoid fuel combustion during generation, without proving every manufacturing or system impact absent. The required benefits are reductions in the specified emissions.
Choose an acid-rain strategy for its pollutant
Catalytic converters in vehicles reduce suitable harmful exhaust components, including oxides of nitrogen; the Extended lesson explains their formation and the required example equation. Low-sulfur fuels reduce the sulfur available to produce SO₂. Flue-gas desulfurisation uses calcium oxide to remove sulfur dioxide from exhaust gases in the school comparison: the basic oxide reacts with the acidic oxide.
Low sulfur does not mean no carbon dioxide from a carbon-containing fuel, and a catalytic converter does not make an engine carbon-free. A basic-oxide treatment intended for SO₂ should not be described as simply filtering every gas out of air. State the target pollutant and explain the relevant chemical or source change; an emissions table can show an improvement for one pollutant without proving every environmental issue solved.
Pause and explain
Which tree-planting explanation matches the required climate link?
Worked example
Explain how low-sulfur fuel and calcium oxide flue-gas treatment address SO₂, then identify a different strategy aimed at CO₂.
Show the worked solution
- Lower fuel sulfur reduces the source of SO₂ on combustion.
- Calcium oxide removes SO₂ through reaction of basic and acidic oxides in the treatment model.
- Decreasing fossil-fuel use reduces combustion-related CO₂; planting trees can increase CO₂ uptake as they grow.
Answer Low-sulfur fuel reduces formation; CaO treatment removes SO₂; lower fossil-fuel use or tree growth addresses the CO₂ link.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Explain planting trees, reducing livestock farming and decreasing fossil-fuel use as climate strategies.
Give me a hint
Attach each strategy to CO₂ uptake, methane sources or CO₂ production.
Compare my reasoning
- Growing trees can increase CO₂ uptake through photosynthesis.
- Less livestock farming can reduce the associated methane emissions.
- Less fossil-fuel combustion reduces its CO₂ emission contribution.
Trees: CO₂ uptake; reduced livestock: methane reduction; less fossil fuel: lower combustion-related CO₂.
Look for these in your work
- All three required strategies are present.
- Each explanation uses the appropriate gas/process.
Explain increasing hydrogen, wind and solar use, then give the three required acid-rain emission strategies.
Give me a hint
Separate changes in energy supply from treatment of specific exhaust pollutants.
Compare my reasoning
- Hydrogen contains no carbon in its reaction; wind/solar generation avoids burning fossil fuel at that stage.
- Vehicle catalytic converters reduce suitable nitrogen-oxide exhaust; low-sulfur fuel lowers SO₂ formation.
- CaO flue-gas desulfurisation removes SO₂ by reaction; production and system impacts still need evidence for broader claims.
Hydrogen and wind/solar can reduce fossil-fuel dependence; catalytic converters, low-sulfur fuels and CaO treatment address specified acid-rain emissions.
Look for these in your work
- The energy and exhaust strategies are separated.
- Each acid-rain strategy has its target explained.
In hypothetical comparable exhaust data, SO₂ falls from 80 to 20 arbitrary units after treatment while CO₂ is unchanged. Find the percentage SO₂ reduction and assess the claim that climate change is now solved.
Give me a hint
Compute the decrease relative to the original SO₂ value, then inspect the separate gas.
Compare my reasoning
- SO₂ decrease is 80−20=60 units.
- Relative decrease is 60/80×100=75%.
- CO₂ is unchanged, and one SO₂ result does not establish every climate process resolved.
75% SO₂ reduction; the separate unchanged CO₂ result does not support the claim that climate change is solved.
Look for these in your work
- The original value is the percentage denominator.
- A pollutant-specific improvement is not made universal.
Common mistakes
- Claiming low-sulfur fuel removes all carbon from the fuel.
- Describing calcium oxide solely as a physical sieve for every gas.
- Calling hydrogen a carbon-containing fuel.
- Promising that one named strategy immediately eliminates all climate change.
What can you explain now?
Explain why calcium oxide is used in the stated flue-gas desulfurisation model.
Compare with the explanation
The basic oxide reacts with acidic sulfur dioxide, removing it from the flue gas.
This chemical removal targets SO₂ rather than every exhaust gas equally.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Match every required climate and acid-rain strategy with its process, then evaluate a pollutant-specific improvement without claiming universal success.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.