O-LevelChemistryBonding & Structure5070/21 · Oct/Nov 2022 · Q28 Marks
Carbon dioxide is a gas at room temperature.
- (a)(i)Draw a dot-and-cross diagram to show the arrangement of electrons in a carbon dioxide molecule. Show only the outer shell electrons.[2]
- (a)(ii)Describe the motion and separation of the particles in a gas. motion separation[2]
- (b)(i)The main processes in the carbon cycle are combustion, respiration and photosynthesis. Name the products of photosynthesis.[1]
- (b)(ii)Some of the reactions in photosynthesis involve enzymes. State the meaning of the term enzyme.[1]
- (c)(i)Carbon dioxide is formed when hydrocarbons are completely combusted. Name the other product of the complete combustion of hydrocarbons.[1]
- (c)(ii)The paraffin (kerosene) fraction from the fractional distillation of petroleum (crude oil) contains hydrocarbons. State one use of the paraffin (kerosene) fraction.[1]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.
- [2] 2 bonding pairs between the C atom and each O atom (1)
- [2] 4 non-bonded electrons on each O atom (1)
- [2] motion: random / fast / rapid (1)
- [2] separation: far apart (1)
- [1] glucose AND oxygen
- [1] biological catalyst / catalyst in organisms
- [1] water
- [1] (fuel) for heating / for cooking / for aircraft engines / lighting / lamps
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