Question
(a) The structures of four organic compounds, P, Q, R and S, are shown.
Answer the following questions about these structures.
Each structure may be used once, more than once or not at all.
(i) State which structure, P, Q, R or S, has a carboxylic acid functional group.[1]
(ii) State which structure, P, Q, R or S, is in the same homologous series as ethane.[1]
(iii) State which structure, P, Q, R or S, decolourises aqueous bromine.[1]
(iv) Deduce the molecular formula of structure Q to show the number of carbon, hydrogen and oxygen atoms.[1]
(b) Structure S is produced by cracking petroleum fractions.
(i) Complete the sentence using a word from the list.
acids alkenes alcohols nitrogen
During cracking, long-chain alkanes are converted to shorter chain alkanes and[1]
(ii) Cracking is an example of thermal decomposition.
State the meaning of the term thermal decomposition.[2]
(c) Link each petroleum fraction on the left to its use on the right.
The first one has been done for you.
Answer/Explanation
Ans:
(a)(i) Q
(a)(ii) S
(a)(iii) R
(a)(iv) C4H8O2
(b)(i) alkenes
(b)(ii) breakdown of a compound (1)
using heat / by heat (1)
(c) naphtha → making chemicals
lubricating fraction → waxes and polishes
kerosene → jet fuel
all 3 correct (2)
1 or 2 correct (1)
Question
(a) The structures of four organic compounds, C, D, E and F, are shown.
Answer the following questions about these compounds.
Each compound may be used once, more than once or not at all.
State which compound, C, D, E or F:
(i) decolourises aqueous bromine [1]
(ii) is an alcohol [1]
(iii) is unsaturated [1]
(iv) is in the same homologous series as ethane. [1]
(b) Petroleum is a mixture of hydrocarbons which can be separated into fractions with different boiling points.
Name the method used to separate these fractions.[1]
(c) Complete the table to show the name and uses of some petroleum fractions.[3]
(d) Some hydrocarbons are formed by the process of cracking.
(i) State the meaning of the term cracking.[2]
(ii) Describe the conditions needed for cracking.[2] [Total: 12]
Answer/Explanation
Ans:
(a)(i) C
(a)(ii) D
(a)(iii) C
(a)(iv) E
(b) (fractional) distillation
(c) refinery gas: heating / cooking (1)
gasoline: fuel for cars / fuel for vehicles (1)
waxes: lubricating (fraction) (1)
(d)(i) breakdown / decomposition of hydrocarbons (1)
idea of long chain hydrocarbons being converted to short chain hydrocarbons (1)
(d)(ii) heat / thermal (decomposition) / high temperature (1)
catalyst (1)
Question
(a) Biogas is a mixture of gases produced when agricultural waste is broken down in the absence of oxygen.
The table compares the percentage by mass of the gases present in two samples of biogas, X and Y.
Answer these questions using only the information in the table.
(i) Deduce the percentage by mass of the other gases in biogas X.[1]
(ii) Describe two major differences in the compositions of biogas X and biogas Y.[2]
1
2
(b) Complete the diagram to show the electronic structure in a methane molecule.
Show only the outer shell electrons.[1]
(c) Hydrogen sulfide burns in air to produce sulfur dioxide and water.
(i) Complete the chemical equation for this reaction.
…..H2S + …..O2 → 2H2O + 2SO2 [2]
(ii) Explain how this equation shows that hydrogen sulfide is oxidized.[1] [Total: 7]
Answer/Explanation
Ans:
(a)(i) 1 (%)
(a)(ii) 1 mark each for any two of:
-
-
- less carbon dioxide in X / more carbon dioxide in Y
- more methane in X / less methane in Y
- less nitrogen in X / more nitrogen in Y
-
(b) 2 electrons in each of the four overlap areas
AND
no unpaired electrons on the hydrogen atoms
(c)(i) 2 (H2S) (1)
3 (O2) (1)
(c)(ii) sulfur has gained oxygen / hydrogen sulfide has gained oxygen