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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 4: Investigate the Hydrolysis of Halogenoalkanes

Aim: To compare the relative rates of hydrolysis of halogenoalkanes with different halogen atoms (Cl, Br, I) and different carbon chain structures (primary, secondary, tertiary).

Chemical Background

Halogenoalkanes undergo nucleophilic substitution when hydrolysed. The rate of hydrolysis depends on:

  1. C–X bond strength (C–I < C–Br < C–Cl):
    Weaker bonds break more easily → faster reaction.
  2. Carbon structure (tertiary > secondary > primary):
    Carbocation stability influences rate.

General Reaction:
R–X + H₂O → R–OH + HX
HX + AgNO₃ → AgX(s) + HNO₃

A precipitate of silver halide (AgX) confirms hydrolysis has occurred.

Safety Notes

Apparatus and Chemicals

Equipment

Chemicals

Procedure

Part 1 – Compare Different Halogens

Halogenoalkane hydrolysis set-up showing formation of silver halide precipitate.
  1. Fill a 250 cm³ beaker with ~50 °C hot water.
  2. Add 5 cm³ ethanol to 3 test tubes.
  3. Add 4 drops of each halogenoalkane:
    • Tube 1: 1-iodobutane
    • Tube 2: 1-bromobutane
    • Tube 3: 1-chlorobutane
  4. Loosely bung each tube and place them in the hot water bath.
  5. In separate tubes, add 5 cm³ silver nitrate solution. Warm in the water bath.
  6. When both solutions reach temperature, mix one pair (e.g. 1-iodobutane + AgNO₃), replace the bung, and start timing.
  7. Record time when first cloudiness (precipitate) appears.
  8. Repeat for other halogenoalkanes.

Part 2 – Compare Carbon Structure

Repeat the above steps with:

Sample Tables of Results

Part 1 – Effect of Halogen

Halogenoalkane Time to first precipitate / s Observed precipitate
1-iodobutane — Yellow (AgI)
1-bromobutane — Cream (AgBr)
1-chlorobutane — White (AgCl)

Part 2 – Effect of Structure

Halogenoalkane Classification Time to first precipitate / s
2-bromo-2-methylpropane Tertiary —
2-bromobutane Secondary —
1-bromobutane Primary —

Analysis of Results

Learning Tips