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Topic: Organic Chemistry
Level: OL/HL
Exam Focus: Section A Practical Skills
1. Experiment Snapshot
Feature
Details
Experiment
Preparation of Ethanoic Acid
Difficulty
⭐⭐⭐ Practical exam standard
Exam Importance
⭐⭐⭐⭐ Organic practicals are common Section A targets
Typical Marks
5–15 marks
2. Aim
To prepare ethanoic acid by oxidising ethanol under reflux.
3. Quick Theory
Ethanol can be oxidised to ethanoic acid using an oxidising agent such as acidified potassium dichromate. Reflux allows heating without losing volatile reactants.
Examiner Tip: Link the practical step to its purpose. This is where students gain easy explanation marks.
Ethanol, acidified potassium dichromate solution or another suitable oxidising mixture.
Safety: Wear goggles. Take care with hot apparatus, organic liquids, bromine water, acids, alkalis and flammable substances.
5. Labelled Practical Diagram
6. Step-by-Step Procedure
Place ethanol and oxidising agent in a reflux flask.
Add anti-bumping granules.
Attach a condenser vertically for reflux.
Heat the mixture gently.
Observe the colour change if dichromate is used.
Collect or identify ethanoic acid product as directed.
7. Observations / Results
Stage
Expected Observation
Dichromate colour
Orange changes to green.
Product smell
Vinegar-like smell may be noticed.
Purpose of reflux
Prevents loss of volatile reactants/products during heating.
8. Sources of Error and Improvements
Source of Error
Improvement
Incorrect heating or poor timing.
Heat gently and follow the sequence carefully.
Product loss or contamination.
Use clean apparatus and correct collection/filtration technique.
Incorrect observation wording.
Use exact exam words such as colourless, precipitate, crystals, reflux, or melting range.
9. Student Common Mistakes
Forgetting that reflux prevents loss of volatile substances.
Writing reduction instead of oxidation.
Not mentioning the orange to green dichromate colour change.
Confusing ethanoic acid with ethanol.
Heating without anti-bumping granules.
10. Examiner Tips and Traps
Examiner Tip: Organic practicals often ask why a step is done, not just what was done.
Examiner Trap: Do not write vague observations like “changed colour” or “gas formed” without the exact result.
11. 🎮 Interactive Simulator
Try It Yourself
What type of reaction converts ethanol to ethanoic acid?
What colour change occurs with acidified dichromate?
Result Window
Ready
Choose the correct actions to complete the practical.
Score:0/0
12. Past Paper Style Questions
State the aim of this experiment. [2]
Describe the preparation method in correct order. [4]
State one safety precaution. [2]
State one observation and its conclusion. [3]
State one common source of error and one improvement. [4]
13. Mark Scheme
Aim correct [2].
Method in correct order with key apparatus/chemicals [4].
Safety point suitable for chemicals/heating [2].
Observation and conclusion linked correctly [3].
Valid error and improvement [4].
14. Quick Revision Card
Aim: To prepare ethanoic acid by oxidising ethanol under reflux.
Key theory: Ethanol can be oxidised to ethanoic acid using an oxidising agent such as acidified potassium dichromate. Reflux allows heating without losing volatile reactants.
Most common mistake: Forgetting that reflux prevents loss of volatile substances.
Exam rule: Use exact observations and state the purpose of key steps.