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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 6: Investigating Chlorination of 2-Methylpropan-2-ol

Aim: To produce and purify a sample of 2-chloro-2-methylpropane by reacting 2-methylpropan-2-ol with concentrated hydrochloric acid, and to isolate the product using separation, drying, and distillation techniques.

Reaction Equation

(CH3)3COH + HCl → (CH3)3CCl + H2O

This is a substitution reaction, where the –OH group is replaced by a Cl atom.

Safety Notes

Apparatus and Chemicals

Equipment

Chemicals

Procedure

Reaction and Separation

Separation funnel setup for chlorination of 2-methylpropan-2-ol
  1. In a fume cupboard, add 10 cm³ 2-methylpropan-2-ol and 35 cm³ conc. HCl to a conical flask. Swirl gently.
  2. Bung the flask, swirl again, then briefly release the pressure.
  3. Repeat gentle swirling and venting for 20 minutes – two layers should form.
  4. Add ~6 g anhydrous calcium chloride to absorb unreacted alcohol.
  5. Transfer mixture to a separating funnel.
  6. Allow layers to settle. Remove and discard the lower aqueous layer.
  7. Add ~20 cm³ sodium hydrogencarbonate solution to neutralise excess acid. Vent frequently due to CO₂.
  8. Remove and discard aqueous layer again.
  9. Dry the organic layer by adding anhydrous sodium sulfate. Swirl and leave until clear.
  10. Decant the dry organic layer into a flask.

Purification – Distillation

Distillation apparatus setup for purification of chloroalkane

Set up for distillation and collect the fraction boiling between 50–52 °C (boiling point of 2-chloro-2-methylpropane). Place purified product into a labelled sample tube.

Test for Chloroalkane (Product Identity)

Silver nitrate test for chloride ions in chloroalkane
  1. Add a few drops of distillate to a test tube with 5 cm³ ethanol and 1 cm³ aqueous sodium hydroxide. Warm in a water bath.
  2. Add nitric acid to acidify.
  3. Add a few drops of silver nitrate solution.
  4. White precipitate = presence of Cl⁻ confirms chloroalkane formation.

Learning Tips

Explanations and Questions

What is removed during sodium hydrogencarbonate washing?
Unreacted HCl (HCl + NaHCO₃ → NaCl + CO₂ + H₂O)

Why is 2-chloro-2-methylpropane insoluble and volatile?
Cannot form hydrogen bonds with water.
Weaker intermolecular forces (dipole and London only).
Lower boiling point (51 °C) vs 82 °C for alcohol.