1.
State what is meant by a hydrocarbon.
[1 mark]
- compound of H and C only
JD SCIENCE
Unit 7 answers — Organic chemistry
Indicative marking points. Award marks for equivalent scientific or mathematical wording. Do not issue this sheet with the student worksheet.
2.
State what is meant by an alkane.
[1 mark]
- saturated hydrocarbon CₙH₂ₙ₊₂
3.
State what is meant by an alkene.
[1 mark]
- unsaturated hydrocarbon CₙH₂ₙ
4.
State what is meant by fractional distillation.
[1 mark]
- separating crude oil by boiling point
5.
State what is meant by cracking.
[1 mark]
- breaking long alkanes into shorter alkanes and alkenes
6.
State what is meant by complete combustion.
[1 mark]
- hydrocarbon + O₂ → CO₂ + H₂O
7.
State what is meant by incomplete combustion.
[1 mark]
- produces CO and/or C
8.
State what is meant by a polymer.
[1 mark]
- long chain of monomers
9.
State what is meant by a functional group.
[1 mark]
- the reactive part of a molecule
10.
State what is meant by an ester.
[1 mark]
- from alcohol + carboxylic acid
11.
Amira is asked about a hydrocarbon in a AQA Chemistry paper.
(a) [2 marks]
- alkanes and alkenes
(b) [3 marks]
- crude oil is a mixture of hydrocarbons
12.
Amira is asked about an alkane in a AQA Chemistry paper.
(a) [2 marks]
- single C–C bonds only
(b) [3 marks]
- used as fuels
13.
Amira is asked about an alkene in a AQA Chemistry paper.
(a) [2 marks]
- contains C=C
(b) [3 marks]
- bromine water decolourises
14.
Amira is asked about fractional distillation in a AQA Chemistry paper.
(a) [2 marks]
- fractionating column
(b) [3 marks]
- larger molecules have higher BP
15.
Amira is asked about cracking in a AQA Chemistry paper.
(a) [2 marks]
- high T and catalyst
(b) [3 marks]
- meets demand for petrol and alkenes
16.
Amira is asked about complete combustion in a AQA Chemistry paper.
(a) [2 marks]
- blue flame
(b) [3 marks]
- plenty of oxygen
17.
Write the formula of the alkane with 5 carbons.
[3 marks]
- Final answer: C5H12
18.
Balance C₃H₈ + O₂ → CO₂ + H₂O
[3 marks]
- Final answer: C₃H₈ + 5O₂ → 3CO₂ + 4H₂O
19.
Mr of C₂H₄ (C=12, H=1)
[3 marks]
- Final answer: 28
20.
A 100 cm³ sample of alkene decolourises bromine water. What does this show?
[3 marks]
- Final answer: C=C present / unsaturated
21.
Percentage of C in CH₄
[3 marks]
- Final answer: 75%
22.
Moles of CO₂ from 2 mol C₂H₆ complete combustion (2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O)
[3 marks]
- Final answer: 4 mol
23.
Amira carries out a AQA-style required practical linked to organic chemistry and fuels. This is a typical AQA required-practical style question.
(a) [2 marks]
- Independent: the independent variable for this topic
- Dependent: the measured outcome
(b) [2 marks]
- keep all other variables constant
- so the test is fair / only one variable is changed
(c) [2 marks]
- repeat and calculate a mean / use a tighter method
24.
Amira carries out collecting valid data for organic chemistry and fuels. This is a typical AQA required-practical style question.
(a) [2 marks]
- Independent: a chosen factor
- Dependent: a quantitative measurement
(b) [2 marks]
- calibrated instrument
- so the test is fair / only one variable is changed
(c) [2 marks]
- systematic error from zero error
25.
Amira carries out drawing a graph for organic chemistry and fuels. This is a typical AQA required-practical style question.
(a) [2 marks]
- Independent: x-variable
- Dependent: y-variable
(b) [2 marks]
- same scale / same apparatus
- so the test is fair / only one variable is changed
(c) [2 marks]
- not drawing a line of best fit through the trend
26.
Amira carries out evaluating a method about organic chemistry and fuels. This is a typical AQA required-practical style question.
(a) [2 marks]
- Independent: method change
- Dependent: precision / accuracy
(b) [2 marks]
- same sample size
- so the test is fair / only one variable is changed
(c) [2 marks]
- too few repeats
27.
Compare a hydrocarbon with an alkane.
[4 marks]
- compound of H and C only
- saturated hydrocarbon CₙH₂ₙ₊₂
- give one linked difference
28.
Compare an alkane with an alkene.
[4 marks]
- saturated hydrocarbon CₙH₂ₙ₊₂
- unsaturated hydrocarbon CₙH₂ₙ
- give one linked difference
29.
Compare an alkene with fractional distillation.
[4 marks]
- unsaturated hydrocarbon CₙH₂ₙ
- separating crude oil by boiling point
- give one linked difference
30.
Compare fractional distillation with cracking.
[4 marks]
- separating crude oil by boiling point
- breaking long alkanes into shorter alkanes and alkenes
- give one linked difference
31.
Apply your knowledge of incomplete combustion to this situation: yellow flame
[3 marks]
- yellow flame
32.
Apply your knowledge of a polymer to this situation: addition polymers from alkenes
[3 marks]
- addition polymers from alkenes