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) Calcium oxide is made by the thermal decomposition of calcium carbonate.
(i) State the meaning of the term thermal decomposition.
(ii) Describe a test for calcium ions.
test ……………………………………………………………………………………………………………………..
observations ………………………………………………………………………………………………………..
(b) Carbon dioxide is produced when dilute hydrochloric acid reacts with calcium carbonate.
\(CaCO_3 + 2HCl → CaCl 2 + CO_2 + H_2O\)
(i) Complete the diagram to show how to measure the volume of carbon dioxide produced during this reaction.
(ii) Describe the effect of each of the following on the rate of reaction of dilute hydrochloric acid with calcium carbonate.
● The concentration of hydrochloric acid is decreased.
All other conditions stay the same.
● The temperature is increased.
All other conditions stay the same.
(c) Carbon dioxide is also formed when the hydrocarbon \(C_3H_8\) is completely combusted.
(i) State the meaning of the term hydrocarbon.
(ii) The hydrocarbon \(C_3H_8\) is called propane.
Name the homologous series that propane belongs to.
(iii) Name two substances formed by the incomplete combustion of propane.
………………………………………………………. and ………………………………………………………
Answer/Explanation
Answer:
(a) (i) breakdown of substance / idea of one substance forming two or more substances (1)
using heat / on heating (1)
(ii) add (aqueous) sodium hydroxide (1)
white precipitate / white solid (1)
OR
add (aqueous) ammonia (1)
no precipitate / very slight white precipitate (1)
(b) (i) gas syringe / upturned measuring cylinder dipping into container (1)
apparatus is workable and airtight (1)
(ii) lower concentration of acid: decreases (in rate) / reaction slower / lower rate / slows down (1)
higher temperature: increases (in rate) / reaction faster / higher rate / speeds up (1)
(c) (i) compound containing hydrogen and carbon only / compound containing hydrogen and carbon and no other substance (2)
if two marks not scored, 1 mark for:
compound containing hydrogen and carbon / it contains hydrogen and carbon only
(ii) alkane(s)
(iii) 1 mark each for any 2 of:
• carbon monoxide
• carbon
• water