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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 12: Preparation of a Transition Metal Complex

Objective: To prepare a transition metal complex: tetraamminecopper(II) sulfate monohydrate, Cu(NH₃)₄SO₄·H₂O.

Reaction Equation

CuSO₄·5H₂O + 4NH₃ → Cu(NH₃)₄SO₄·H₂O + 4H₂O

Safety

Apparatus and Chemicals

Apparatus

Chemicals

Procedure

Formation of tetraamminecopper(II) complex in the lab using copper (II) sulfate, concentrated NH3, ethanol and an ice bath Edexcel A-Level chemistry core practical 12
  1. Weigh between 1.4 g and 1.6 g of copper(II) sulfate.
    • Weigh the empty test tube first, then again after adding the solid.
    • The difference is the mass of copper(II) sulfate used.
  2. Dissolve the solid in 4 cm³ of water using a graduated pipette.
    • Stand the test tube in a 100 cm³ beaker containing hot water to gently heat it.
    • Stir to aid dissolution, then remove from water bath once dissolved.
  3. In a fume cupboard, add 2 cm³ concentrated ammonia solution slowly while stirring.
  4. Transfer the contents into 6 cm³ cold ethanol in a beaker. Mix and cool the mixture in an ice bath.
  5. Filter the blue crystals using a Büchner funnel. Buchner filtration of tetraamminecopper(II) complex from copper (II) sulfate, concentrated NH3, ethanol and an ice bath Edexcel A-Level chemistry core practical 12
    • Rinse the original test tube with cold ethanol and add washings to the funnel.
    • Rinse crystals with cold ethanol.
  6. Dry the product:
    • Transfer crystals to dry filter paper, cover with another, and pat dry.
    • Repeat with fresh paper until dry.
  7. Weigh the dried crystals and record the mass.

Calculations

Example based on 1.5 g starting material

Moles of CuSO₄·5H₂O used = 1.5 ÷ 249.5 = 0.00601 mol
Theoretical yield = 0.00601 × 245.5 = 1.48 g
Actual yield (example) = 1.2 g
% yield = (1.2 ÷ 1.48) × 100 = 81%

Possible Reasons for Yield Loss or Gain