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O Level Chemistry Organic Chemistry Quiz

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Questions

O-Level Chemistry Quiz - Organic Chemistry

Name: __________________________
Class: __________________________
Date: __________________________
Score: ________ / 40

Duration: 45 minutes
Total Marks: 40

Instructions:

Answer all questions.
Write your answers in the spaces provided.
The number of marks is given in brackets [ ] at the end of each question or part question.
You may use a calculator.

Section A: Multiple Choice & Short Concepts (10 Marks)

1. Which statement about homologous series is incorrect?
A. Members have the same general formula.
B. Members have similar chemical properties.
C. Members show a gradation in physical properties.
D. Members have the same molecular formula.
[1]

2. Which compound is an isomer of butane?
A. Propane
B. Pentane
C. 2-methylpropane
D. Butene
[1]

3. Ethene reacts with steam to form ethanol. What type of reaction is this?
A. Addition
B. Substitution
C. Polymerisation
D. Combustion
[1]

4. Which reagent is used to distinguish between ethane and ethene?
A. Aqueous sodium hydroxide
B. Aqueous bromine
C. Dilute hydrochloric acid
D. Limewater
[1]

5. What is the general formula for the homologous series of alcohols?
A. $C_nH_{2n}$
B. $C_nH_{2n+2}$
C. $C_nH_{2n+1}OH$
D. $C_nH_{2n}O_2$
[1]

6. Name the process used to separate crude oil into fractions such as petrol and diesel.

[1]

7. State the name of the functional group present in ethanoic acid.

[1]

8. Complete the equation for the complete combustion of methane:
$CH_4 + 2O_2 \rightarrow$ _______________ + _______________
[1]

9. What is the product formed when ethanol is oxidised using acidified potassium manganate(VII)?

[1]

10. Define the term saturated as applied to hydrocarbons.

[1]

Section B: Structured Questions (20 Marks)

11. The table below shows some properties of the first four members of the alkene homologous series.

Name	Molecular Formula	Boiling Point (°C)	State at r.t.p.
Ethene	$C_2H_4$	-104	Gas
Propene	$C_3H_6$	-47	Gas
Butene	$C_4H_8$	-6	Gas
Pentene	$C_5H_{10}$	30	Liquid

(a) Deduce the molecular formula of hexene.

[1]

(b) Describe the trend in boiling points as the number of carbon atoms increases.

[1]

[2]

(d) Write a balanced chemical equation for the reaction of propene with hydrogen.

[2]

12. Ethanol can be produced by two different methods: fermentation of glucose and the catalytic addition of steam to ethene.

(a) Write the chemical equation for the fermentation of glucose ( $C_6H_{12}O_6$ ).

[2]

(b) State two conditions required for fermentation.

[2]

[1]

(d) Ethanol reacts with ethanoic acid in the presence of concentrated sulfuric acid to form an ester.
(i) Name the ester formed.

[1]
(ii) Draw the structural formula of this ester, showing all atoms and bonds.
 
[2]

13. Poly(ethene) is a widely used plastic.

(a) Draw the structure of the monomer used to make poly(ethene).
 
[1]

(b) Draw the structure of the repeating unit of poly(ethene).
 
[1]

[1]

(d) Suggest one method, other than landfill, for disposing of waste plastics and state one environmental benefit of this method.
Method: ___________________________________________________________________
Benefit: __________________________________________________________________
[2]

14. A student performs a test on an unknown liquid X.

Liquid X burns with a clean blue flame.
Liquid X reacts with sodium metal to produce hydrogen gas.
Liquid X turns acidified potassium dichromate(VI) from orange to green upon heating.

(a) Identify the homologous series to which liquid X belongs.

[1]

(b) Write the equation for the reaction of liquid X (assume it is ethanol) with sodium.

[2]

15. Cracking is an important process in the petroleum industry.

(a) Define cracking.

[2]

(b) Decane ( $C_{10}H_{22}$ ) is cracked to produce ethene and another hydrocarbon Y.
$C_{10}H_{22} \rightarrow C_2H_4 + Y$
Determine the molecular formula of Y.

[1]

(d) Explain why cracking is necessary in the oil industry.

[2]

16. The following scheme shows the conversion of ethene into various products.

$\text{Ethene} \xrightarrow{\text{Reaction 1}} \text{Poly(ethene)}$ $\text{Ethene} \xrightarrow{\text{Reaction 2}} \text{Ethanol}$ $\text{Ethanol} \xrightarrow{\text{Reaction 3}} \text{Ethanoic Acid}$

(a) Name the type of polymerisation occurring in Reaction 1.

[1]

(b) State the reagent and conditions for Reaction 2.
Reagent: __________________________
Conditions: ________________________
[2]

17. Consider the reaction of ethene with hydrogen bromide.

(a) Name the product formed.

[1]

(b) What type of reaction is this?

[1]

18. Methane is the primary component of natural gas.

(a) Write the equation for the reaction of methane with chlorine in the presence of ultraviolet light to form chloromethane.

[2]

(b) Name the type of reaction described in 18(a).

[1]

19. Esters are used as flavourings and solvents.

(a) Name the alcohol and carboxylic acid required to make propyl ethanoate.
Alcohol: __________________________
Carboxylic Acid: __________________________
[2]

(b) State one physical property characteristic of esters.

[1]

20. Polymers can be classified as thermoplastics or thermosetting plastics.

(a) State one difference between thermoplastics and thermosetting plastics regarding their response to heat.

[1]

(b) Give one example of a thermosetting plastic.

[1]

Answers

O-Level Chemistry Quiz - Organic Chemistry (Answer Key)

Total Marks: 40

Section A: Multiple Choice & Short Concepts

1. D
Reasoning: Members of a homologous series have different molecular formulas (differing by $CH_2$ ). Same molecular formula implies isomers, not a series. [1]

2. C
Reasoning: Butane is $C_4H_{10}$ . 2-methylpropane is also $C_4H_{10}$ but with a branched structure. [1]

3. A
Reasoning: The double bond opens up to add water molecules. [1]

4. B
Reasoning: Alkenes decolourise aqueous bromine (orange to colourless); alkanes do not. [1]

5. C
Reasoning: Alcohols contain the -OH group attached to a saturated carbon chain. [1]

6. Fractional distillation [1]

7. Carboxyl group (or Carboxylic acid group) [1]

8. $CO_2 + 2H_2O$ [1]
(Accept $CO_2$ and $H_2O$ separately)

9. Ethanoic acid [1]

10. Contains only single bonds between carbon atoms (or contains the maximum number of hydrogen atoms per carbon). [1]

Section B: Structured Questions

11. (a) $C_6H_{12}$ [1] (b) Boiling point increases as the number of carbon atoms increases. [1] (c) As the chain length/size of the molecule increases, the strength of the intermolecular forces (van der Waals forces) increases. More heat energy is required to overcome these forces. [2] (d) $C_3H_6 + H_2 \rightarrow C_3H_8$ [2]
(1 mark for correct formulas, 1 mark for balancing)

12. (a) $C_6H_{12}O_6 \rightarrow 2C_2H_5OH + 2CO_2$ [2]
(1 mark for correct products, 1 mark for balancing) (b) Any two:

Temperature around 30-40°C (warm)
Absence of oxygen (anaerobic conditions)
Presence of yeast (enzymes)
[2] (c) Any one:
The process is continuous (fermentation is batch).
The product is pure (fermentation produces dilute solution requiring distillation).
Faster reaction rate.
[1] (d) (i) Ethyl ethanoate [1]
(ii)

      H   O
      |   ||
H - C - C - O - C - H
      |       |
      H       H

(Must show all atoms and bonds. Correct linkage -COO- is essential.) [2]

13. (a)

[1] (b)

      H   H
      |   |
  - C - C -
      |   |
      H   H

(Brackets and 'n' are not strictly required for the repeating unit drawing unless asked for the polymer formula, but bonds must extend outwards.) [1] (c) It is non-biodegradable (does not rot/decompose easily by bacteria). [1] (d) Method: Recycling (or Incineration with energy recovery).
Benefit: Conserves crude oil resources (or Generates electricity/heat). [2]

14. (a) Alcohols [1] (b) $2C_2H_5OH + 2Na \rightarrow 2C_2H_5ONa + H_2$ [2]
(1 mark for correct organic salt formula, 1 mark for balancing including $H_2$ )

15. (a) The breaking down of long-chain hydrocarbons (alkanes) into shorter-chain hydrocarbons (alkanes and alkenes) by heat/catalyst. [2] (b) $C_8H_{18}$ [1]
(Conservation of mass: C: 10-2=8, H: 22-4=18) (c)

    H   H   H   H   H   H   H   H
    |   |   |   |   |   |   |   |
H - C - C - C - C - C - C - C - C - H
    |   |   |   |   |   |   |   |
    H   H   H   H   H   H   H   H

(Octane structure. Accept condensed structural formula $CH_3(CH_2)_6CH_3$ if clear.) [2] (d) To match supply and demand; short-chain hydrocarbons (like petrol) are in higher demand than long-chain fractions. Or: To produce alkenes for polymer production. [2]

16. (a) Addition polymerisation [1] (b) Reagent: Steam (or Water) [1]
Conditions: Catalyst (Phosphoric acid), High Temperature (300°C), High Pressure (60-70 atm). [1]
(Accept "Catalyst and Heat" for 1 mark if specific details missing, but O-Level usually requires specific catalyst mention for full credit in some schemes, here 1 mark for conditions broadly).

17. (a) Bromoethane [1] (b) Addition [1]

18. (a) $CH_4 + Cl_2 \rightarrow CH_3Cl + HCl$ [2]
(1 mark for correct organic product, 1 mark for balancing/including HCl) (b) Substitution [1]

19. (a) Alcohol: Propanol (or Propan-1-ol) [1]
Carboxylic Acid: Ethanoic acid [1] (b) Volatile / Sweet smell / Fruity smell / Low boiling point. [1]

20. (a) Thermoplastics soften/melt on heating and can be remoulded; Thermosetting plastics do not soften/melt on heating (they char/decompose). [1] (b) Melamine / Bakelite / Urea-formaldehyde. [1]