Edexcel IGCSE Chemistry Alcohols questions

Revise the key specification points for Alcohols, then try focused exam-style questions with worked explanations.

Edexcel IGCSE Chemistry Subtopic 4.e

What You Need To Know

Alcohols questions can test recall, explanation, calculations, practical method, or data handling. For this subtopic, you should be able to:

  • 4.29C know that alcohols contain the functional group −OH
  • 4.30C understand how to draw structural and displayed formulae for methanol, ethanol, propanol (propan-1-ol only) and butanol (butan-1-ol only), and name each compound the names propanol and butanol are acceptable
  • 4.31C know that ethanol can be oxidised by: burning in air or oxygen (complete combustion) reaction with oxygen in the air to form ethanoic acid (microbial oxidation) heating with potassium dichromate(VI) in dilute sulfuric acid to form ethanoic acid
  • 4.32C know that ethanol can be manufactured by: reacting ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300 ºC and a pressure of about 60–70 atm the fermentation of glucose, in the absence of air, at an optimum temperature of about 30 ºC and using the enzymes in yeast
  • 4.33C understand the reasons for fermentation, in the absence of air, and at an optimum temperature

How To Answer Alcohols Questions

  1. Start by identifying exactly which specification point the question is testing.
  2. Use the command word carefully: state and identify need a direct answer, while describe and explain need linked detail.
  3. For tables, graphs, diagrams, and practical questions, quote the relevant observation or reading before drawing a conclusion.
  4. When a question asks for a calculation, show the key substitution and include units where they are needed.

Example Questions With Worked Explanations

Example 1: Core Knowledge

Question 1

This question is about the unsaturated hydrocarbon, ethene.
The displayed formula of ethene is
Displayed formula of ethene showing two carbon atoms joined by a double bond (C=C), each carbon bonded to two hydrogen atoms (H2C=CH2). Ethanol is produced industrially by the reaction between ethene and steam.
The equation for the reaction is
CH2CH2(g) + H2O(g) → CH3CH2OH(l)
State the temperature and pressure used in this reaction.
temperature
pressure

Final answer

temperature = 300 °C
pressure = 60–70 atm

Mark scheme points

  1. M1 Temperature stated as 300 °C.
  2. M2 Pressure stated as 60–70 atmospheres (atm).

Explanation

For the industrial production of ethanol from ethene and steam, you need the standard hydration conditions:

  • Write the temperature as 300 °C.
  • Write the pressure as 60–70 atm.

These are the values to learn and use in an exam. A value in the accepted range would also gain credit, but the safest full-mark answer is the standard pair above.

temperature: 300 °C
pressure: 60–70 atm

Common mistakes

  • Confusing this process with fermentation and giving about 30 °C instead of 300 °C.
  • Giving only one condition and losing the other mark.
  • Writing a very low pressure such as 1 atm instead of 60–70 atm.
  • Adding other facts, such as the catalyst, but forgetting to state the actual temperature and pressure.

Example 2: Core Knowledge

Question 2

Compounds containing C C double bonds are used to manufacture alcohols such as ethanol and addition polymers such as PVC.
The table shows the formulae of some compounds containing C C bonds.
A B
CH2 CH2 Displayed formula for compound B: three carbon atoms in a chain with a C=C double bond between the first and second carbon; hydrogens shown attached (propene-type displayed structure).
C D
C4H8 C2H3Cl
(b) Ethanol can be manufactured from compound A using reaction 1.
Ethanol can also be manufactured from glucose using reaction 2.
The equations for these reactions are
reaction 1  C2H4 + H2O → C2H5OH
reaction 2  C6H12O6 → 2C2H5OH + 2CO2
Give two advantages of using each reaction to manufacture ethanol.
reaction 2

Final answer

Any two from each list:

  • reaction 1
    • produces pure(r) ethanol
    • is faster
    • has greater atom economy
    • does not produce CO2
  • reaction 2
    • uses renewable / sustainable resources
    • uses atmospheric pressure / does not need high pressure
    • works at low temperature / does not need much heating energy

Mark scheme points

  1. M1 Reaction 1 produces pure(r) ethanol / alcohol / product.
  2. M2 Reaction 1 is a faster reaction.
  3. M3 Reaction 1 has greater atom economy.
  4. M4 Reaction 1 does not produce carbon dioxide, so there is less pollution.
  5. M5 Reaction 2 uses renewable / sustainable resources, rather than finite resources.
  6. M6 Reaction 2 uses atmospheric pressure / does not need high pressure.
  7. M7 Reaction 2 works at low temperature / just above room temperature, so little heat energy is needed.

Explanation

You need four separate advantages in total: two for reaction 1 and two for reaction 2.

  • For reaction 1, the accepted ideas are about the product being purer, the process being faster, having better atom economy, or producing no CO2.
  • For reaction 2, the accepted ideas are that it uses renewable raw materials, works at low pressure, and works at low temperature.

A very safe full-mark answer would be:

  • reaction 1: produces purer ethanol; faster reaction
  • reaction 2: uses renewable resources; works at low temperature / pressure

Keep each point short and distinct. Do not repeat the same idea in different words.

Common mistakes

  • Giving only two advantages in total instead of two for each reaction.
  • Writing vague answers such as “better” without saying why.
  • Saying “lower cost” or “cheaper” — this is not credited.
  • For reaction 1, saying “more concentrated ethanol” — this is ignored.
  • For reaction 2, forgetting that the valid advantages are mainly renewable resources, low pressure, and low temperature.

Practise This Subtopic

Build a focused practice set on alcohols, with questions selected from this part of the Edexcel IGCSE Chemistry specification.

Generate Alcohols questions View Organic chemistry Topic Page