Page 54 - ACE YR IGCSE A TOP APPROACH TO CHEM

11 C (b) Cause global warming [1]
Lime kiln is used to produce quicklime, CaO. Carbon dioxide absorbs heat and prevents it
Thermal decomposition: from escaping back into space. [1]
CaCO ➞ CaO + CO 2
3
The raw material, CaCO should be added from Y. (c) Trees use carbon dioxide [1]
3
CO which is released during the process should exit at X in photosynthesis [1]
2
because it is a gas that has very low density.
The product, CaO, is a solid at 600-700 K. It should be (d) Methane [1]
collected at Z. (e) Produce only water [1]
2H + O ➞ 2H O
Part 2: Structured Questions 2 2 2
1 (a) Anhydrous copper(II) sulfate [1] 4 (a) Nitrogen [1]
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White to blue [1] and oxygen react [1]
or at high temperatures in car engines [1]
Anhydrous cobalt(II) chloride [1] (b) N + O ➞ 2NO [1]
2
2
Blue to pink [1] N O , N O and NO are all possible oxides of nitrogen.
2
2
2
2
Note: Must always include the expected result.
Anhydrous = does not contain water (c) Cause acid rain [1]
Oxides of nitrogen are acidic. They dissolve in water
(b) Filter away the fine particles [1] to form nitric acid.
(c) Add chlorine [1] (d) The oxides of nitrogen pass through the
Chlorine kills bacteria. catalytic converter [1]
to form oxygen and nitrogen. [1]
(d) To prevent tooth decay [1] Oxygen reacts with carbon monoxide [1]
Fluorine is commonly used in toothpaste. to form carbon dioxide. [1]
(e) Add carbon [1] Oxygen and nitrogen are the main constituents of
air. They are harmless.
(f) Any two from: [2] Carbon dioxide is naturally occurring and it is less
• Cool hot machinery poisonous than carbon monoxide.
• As a solvent
• Washing (e) Cause respiratory problems [1]
• Move the turbines with steam Particulates can cause health problems for humans
because they irritate the lining of the lungs. The
(g) Does not contain impurities [1] smaller particulates are able to travel deeper into
2 (a) Liquefy the air [1] the lung tissues and cause damage.
Heat and condense the air / Fractional 5 (a) 3 Some of the energy is reflected away as
distillation [1] thermal energy. [1]
Both gases have different boiling points. So, 4 Some thermal energy is lost to space. [1]
fractional distillation is suitable to separate them. 5 Some of the energy is absorbed by greenhouse
(b) Carbon dioxide [1] gases and stays in the atmosphere. [1]
Argon / Any noble gas [1]
Carbon dioxide is not a pollutant. It is released (b) (i) The Earth is warming up. [1]
during respiration. Carbon monoxide is a pollutant. (ii) Climate change [1]
It should not present in the pure air. (iii) Any two from: [2]
(c) (i) Burning of coal / fossil fuel [1] • Droughts
Coal or fossil fuel contains sulfur. • The melting of icebergs
Sulfur reacts with oxygen in burning. • Sea level rises
(ii) Sulfur dioxide dissolves and reacts with • Storms
water [1] • Floods
forms sulfuric acid [1] • The extinction of species
2SO + 2H O + O ➞ 2H SO • Disease transmission
2 2 2 2 4 • Wildfires
(iii) H SO + CaCO ➞ CaSO + CO + H O
4
2
2
2
4
3
[1] (c) Any two from: [2]
(iv) Damage the nervous system [1] • Use wind / waves / tides / fast flowing rivers
to generate energy
3 (a) Carbon monoxide is toxic. [1] • Use nuclear energy
Reduce the amount of oxygen transported to • Use solar energy
the body. [1] • Use hydrogen-oxygen fuel cells
Carbon monoxide will bond with haemoglobin. Less
haemoglobin can take up oxygen for the body. Cells
die of oxygen starvation.
Cambridge IGCSE TM
166 Ace Your Chemistry

Answers.indd 166 3/4/22 3:54 PM