Cambridge IGCSE · Chemistry 0620
IGCSE Chemistry: Chemistry of the environment — Practice Questions & Answers
Testing and treating water, fertilisers and eutrophication, the composition of clean air, pollutants, catalytic converters and greenhouse gases.
522 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
Which chemical test confirms the presence of water?
- Anhydrous copper(II) sulfate turns from white to blue
- Limewater turns milky
- Damp litmus paper turns red
- A glowing splint relights
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WhyAnhydrous copper(II) sulfate turns from white to blue when water is added, confirming water is present.
2
Multiple choice · Easy
What is the approximate percentage of nitrogen in clean, dry air?
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WhyClean dry air is about 78% nitrogen, the most abundant gas in the atmosphere.
3
Multiple choice · Easy
Which gas makes up about 21% of clean, dry air?
- Oxygen
- Carbon dioxide
- Argon
- Nitrogen
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WhyOxygen makes up approximately 21% of clean dry air, the second most abundant gas.
4
Multiple choice · Easy
Which of these is a greenhouse gas that contributes to climate change?
- Carbon dioxide
- Nitrogen
- Oxygen
- Argon
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WhyCarbon dioxide (CO2) is a greenhouse gas that traps heat in the atmosphere and contributes to climate change.
5
Multiple choice · Easy
Which three elements are supplied by an NPK fertiliser?
- Nitrogen, phosphorus and potassium
- Nitrogen, phosphorus and potassium oxide only
- Nitrogen, phosphorus and carbon
- Sodium, phosphorus and potassium
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WhyNPK fertilisers supply nitrogen (N), phosphorus (P) and potassium (K) to help plants grow.
6
Fill in the blank · Easy
The boiling point of pure water at standard pressure is degrees Celsius.
Answer:
100
WhyPure water boils at exactly 100 degrees Celsius at standard atmospheric pressure; impurities raise this value.
7
Multiple choice · Medium
Which air pollutant is produced when sulfur impurities in fuels are burned?
- Sulfur dioxide
- Carbon monoxide
- Methane
- Nitrogen dioxide
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WhyBurning fuels containing sulfur impurities produces sulfur dioxide (SO2), which causes acid rain.
8
Multiple choice · Medium
Why is carbon monoxide a dangerous air pollutant?
- It is toxic and reduces the blood's ability to carry oxygen
- It causes acid rain
- It depletes the ozone layer
- It turns limewater milky
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WhyCarbon monoxide is toxic because it binds to haemoglobin, reducing the blood's ability to carry oxygen around the body.
9
Multiple choice · Medium
How is carbon monoxide formed in a car engine?
- Incomplete combustion of carbon-containing fuels
- Complete combustion of hydrogen
- Reaction of nitrogen with oxygen
- Burning of sulfur impurities
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WhyCarbon monoxide forms from the incomplete combustion of carbon-containing fuels when there is insufficient oxygen.
10
Multiple choice · Medium
Distilled water is used in chemical experiments rather than tap water because tap water
- contains dissolved salts that may interfere with results
- has a higher boiling point than 100 degrees C always
- is too acidic for all reactions
- contains no dissolved oxygen
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WhyTap water contains dissolved salts and other substances that can interfere with experiments, so distilled (pure) water is preferred.
Key terms in Chemistry of the environment
Anhydrous copper(II) sulfate: A white solid used to test for the presence of water, turning blue when water is added.
Cobalt(II) chloride paper: A test paper that changes from blue to pink in the presence of water.
Test for water: Confirmed by using anhydrous copper(II) sulfate turning blue or cobalt(II) chloride paper turning from blue to pink.
Pure water boiling point: Pure water boils at exactly 100 degrees Celsius at standard atmospheric pressure.
Pure water melting point: Pure water freezes and melts at exactly 0 degrees Celsius at standard atmospheric pressure.
Test for purity of water: Pure water can be confirmed by measuring its boiling point of 100 degrees Celsius and melting point of 0 degrees Celsius.
Impure water: Water containing dissolved substances that boils above 100 degrees Celsius and freezes below 0 degrees Celsius.
Distilled water: Water that has been purified by distillation to remove dissolved solids and most impurities.
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