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*Revision Materials and Past Papers* 1 Atomic Structure and the Periodic Table 2 Bonding and Structure 3 Redox I 4 Inorganic Chemistry and the Periodic Table 5 Formulae, Equations and Amounts of Substance 6 Organic Chemistry I 7 Modern Analytical Techniques I 8 Energetics I 9 Kinetics I 10 Equilibrium I 11 Equilibrium II 12 Acid-base Equilibria 13 Energetics II 14 Redox II 15 Transition Metals 16 Kinetics II 17 Organic Chemistry II 18 Organic Chemistry III 19 Modern Analytical Techniques II RP Required Practicals

Required Practicals

1 Measuring the molar volume of a gas 2 Preparation of a standard solution from a solid acid 3 Finding the concentration of a solution of hydrochloric acid 4 Investigation of the rates of hydrolysis of halogenoalkanes 5 The oxidation of ethanol 6 Chlorination of 2-methylpropan-2-ol with concentrated hydrochloric acid 7 Analysis of some inorganic and organic unknowns 8 To determine the enthalpy change of a reaction using Hess’s Law 9 Finding the Ka value for a weak acid 10 Investigating some electrochemical cells 11 Redox titration 12 The preparation of a transition metal complex 13 Following the rate of the iodine-propanone reaction by titrimetric method and investigating a clock reaction (Harcourt-Esson iodine clock) 14 Finding the activation energy of a reaction 15 Analysis of some inorganic and organic unknowns 16 The preparation of aspirin

Core Practical 5: Investigate the Oxidation of Ethanol

Aim: To oxidise ethanol to ethanoic acid using acidified sodium dichromate, applying reflux and distillation, and to test the properties of the distillate.

Key Concepts

Primary alcohols like ethanol are oxidised in two steps

  1. Ethanol → Ethanal (distillation)
  2. Ethanol → Ethanoic acid (reflux)

In this practical, oxidation is carried out under reflux, then the product (mainly ethanoic acid) is isolated by distillation.

Reaction Equations

Oxidation: CH3CH2OH + 2[O] → CH3COOH + H2O

Test with Magnesium: 2CH3COOH + Mg → (CH3COO)2Mg + H2

Test with Calcium Carbonate: 2CH3COOH + CaCO3 → (CH3COO)2Ca + CO2 + H2O

Safety Notes

Apparatus and Chemicals

Apparatus

Chemicals

Procedure

Reflux Setup

Reflux setup for oxidising ethanol
  1. Cool 20 cm³ of acidified sodium dichromate in a pear-shaped flask (ice-water bath).
  2. Add anti-bumping granules.
  3. Using a pipette, add 1 cm³ ethanol drop by drop down the condenser.
  4. Allow to stand 5 minutes.
  5. Heat in a boiling water bath for 20 minutes under reflux.
  6. Allow to cool.

Distillation

Distillation setup for oxidising ethanol

Set up distillation apparatus and collect 3–4 cm³ of clear, colourless liquid.

Analysis of Product

  1. pH test: Use universal indicator → expected pH ~3.5 (acidic).
  2. Acidified potassium dichromate: No colour change (ethanol fully oxidised).
  3. Calcium carbonate: Effervescence → CO₂ present.
  4. Magnesium ribbon: Effervescence → H₂ gas present.
  5. Fehling’s solution: No red ppt → no aldehyde, full oxidation.

Sample Observations

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Matt’s exam tip

Reflux = complete oxidation (alcohol → carboxylic acid). Distillation = partial oxidation (alcohol → aldehyde).