Skip to content
Dabour HubLEARN · PRACTICE · EXPLORESign inStudent

3.2.3Unit 3. Practical Skills in Chemistry I

Propan-1-ol Oxidation — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions

5 min read 6 parts Lesson 9 of 10 Unit quiz

📚 IAL Edexcel Linear (Chemistry) Hub / Topical Revision
🩺
100% Curriculum Specification Match Lesson Doctor Verified
The only platform with 100% curriculum specification match and verified interactive question banks.
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
0%read

Part 1 of 6The Chemistry

A primary alcohol can be oxidised in two stages.

Stage 1
  • Stage 1 CH₃CH₂CH₂OH + [O] → CH₃CH₂CHO + H₂O: propan-1-ol is oxidised to the aldehyde propanal.
Stage 2
  • Stage 2 CH₃CH₂CHO + [O] → CH₃CH₂COOH: propanal is oxidised further to propanoic acid.
Oxidant
  • Oxidant Acidified potassium dichromate(VI) turns from orange to green as dichromate(VI) is reduced to chromium(III).
Boiling points
  • Boiling points Propanal boils at about 49 °C, propan-1-ol at 97 °C and propanoic acid at 141 °C.

Part 2 of 6Making the Aldehyde

The product is distilled off as soon as it forms.

1
Cool acidified potassium dichromate(VI) solution in a flask in an ice bath and add anti-bumping granules.
2
Add the propan-1-ol slowly, drop by drop, using a dropping funnel or pipette to control the exothermic reaction.
3
Warm the mixture gently with a water bath or electric heater, never a naked flame, because the alcohol is flammable.
4
Propanal has the lowest boiling point, so it vaporises first and passes through the condenser into the receiver.
5
Collect the distillate, which stops further oxidation because the aldehyde is removed from the oxidising agent.

Part 3 of 6Making the Acid

Making the Acid
Reflux
  • Reflux Heat the alcohol with excess acidified dichromate under reflux for about 20 minutes, with a vertical condenser fitted.
Why reflux
  • Why reflux The condenser returns propanal vapour to the flask, giving it time to be oxidised all the way to the acid.
Excess oxidant
  • Excess oxidant A surplus of dichromate(VI) ensures that the aldehyde is not left unoxidised.
Separation
  • Separation After the reflux, set the apparatus up for distillation to separate the carboxylic acid product from the reaction mixture.

Part 4 of 6Hazards and Precautions

Flammable alcohol
  • Flammable alcohol Propan-1-ol vapour is flammable and irritates the eyes, so avoid naked flames and use small quantities.
Oxidiser
  • Oxidiser Potassium dichromate(VI) is a strong oxidising agent and a health hazard, so avoid skin contact and clean up spills at once.
Ventilation
  • Ventilation Use a fume cupboard to avoid breathing in vapours of the alcohol, aldehyde or acid.
Heating
  • Heating Never heat with a naked flame, and always add the alcohol slowly to avoid a violent reaction.

Part 5 of 6Worked Example

Question

  • 1.00 cm³ of propan-1-ol (density 0.80 g cm⁻³, Mr = 60.0) is oxidised and 0.46 g of propanal (Mr = 58.0) is collected.
  • Calculate the percentage yield.

  1. Mass of propan-1-ol = 1.00 × 0.80 = 0.80 g.
  2. n = 0.80 ÷ 60.0 = 0.01333 mol; one mole of alcohol gives one mole of propanal.
  3. Theoretical mass of propanal = 0.01333 × 58.0 = 0.773 g.
  4. Percentage yield = 0.46 ÷ 0.773 × 100 = 59.5 %.

Answer Percentage yield = 59.5 %

Part 6 of 6Exam Checklist & Tips

3.2.3 – Key Points for the Exam

  • Reflux Heating a reaction mixture with a vertical condenser so that vapours return to the flask.
  • Distillation Separating a liquid by boiling it and condensing the vapour in a separate vessel.
  • Aldehyde A compound containing the –CHO group, formed by partial oxidation of a primary alcohol.
  • Anti-bumping granules Small pieces added to a liquid before heating to make boiling smooth.

Common Mistakes

  • Heating the mixture with the aldehyde under reflux when only partial oxidation to the aldehyde is required.
  • Adding the alcohol quickly to hot dichromate, which can cause a violent reaction.
  • Placing a thermometer incorrectly so it does not measure the vapour temperature at the condenser.
  • Using a naked flame to heat a flask containing flammable propan-1-ol.

Last updated:

\n