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*Revision Materials and Past Papers* 1 Atomic Structure 2 Amounts of Substance 3 Bonding 4 Energetics 5 Kinetics 6 Chemical Equilibria & Kc 7 Redox Equations 8 Thermodynamics 9 Rate Equations 10 Kp (Equilibrium Constant) 11 Electrode Potentials & Cells 12 Acids and Bases 13 Periodicity 14 Group 2: Alkaline Earth Metals 15 Group 7: The Halogens 16 Period 3 Elements & Oxides 17 Transition Metals 18 Reactions of Ions in Aqueous Solution 19 Intro to Organic Chemistry 20 Alkanes 21 Halogenoalkanes 22 Alkenes 23 Alcohols 24 Organic Analysis 25 Optical Isomerism 26 Aldehydes & Ketones 27 Carboxylic Acids & Derivatives 28 Aromatic Chemistry 29 Amines 30 Polymers 31 Amino Acids, Proteins & DNA 32 Organic Synthesis 33 NMR Spectroscopy 34 Chromatography RP1–RP12 Required Practicals

7.2 Required Practicals

1 Make up a volumetric solution and carry out a simple acid–base titration 2 Measurement of an enthalpy change 3 Investigation of how the rate of a reaction changes with temperature 4 Carry out simple test-tube reactions to identify cations anions 5 Distillation of a product from a reaction 6 Tests for alcohol, aldehyde, alkene and carboxylic acid 7 Measuring the rate of reaction, by an initial rate method, by a continuous monitoring method 8 Measuring the EMF of an electrochemical cell 9 Investigate how pH changes when a weak acid reacts with a strong base and when a strong acid reacts with a weak base 10 Preparation of, a pure organic solid and test of its purity, a pure organic liquid 11 Carry out simple test-tube reactions to identify transition metal ions in aqueous solution 12 Separation of species by thin-layer chromatography

Disclaimer:
The exact reagents, reactions, processes and equipment used in practical activities may vary between schools, colleges, and exam board exemplar methods. The essential techniques, skills, and learning objectives remain the same. Always follow the instructions, risk assessments, and safety guidance provided by your teacher or centre.


PRACTICAL 8 – Electrochemical Cells

Aim:
To measure the EMF (electromotive force) of an electrochemical cell and to compare the electrode potentials of different metals.

Overview:
Investigate and compare electrode potentials by measuring EMFs of standard and comparative electrochemical cells under controlled conditions.


Part 1: Measuring the EMF of a Standard Cell

Key Concepts

Apparatus and Chemicals

Method Summary

AQA A-Level Chemistry copper–zinc electrochemical cell with CuSO4, ZnSO4, salt bridge, and voltmeter setup.
  1. Clean copper and zinc strips using emery paper and degrease with propanone.
  2. Place each metal in its respective solution in separate beakers (50 cm3 each).
  3. Fill U-tube with NaCl(aq) and stopper ends with NaCl(aq) soaked cotton wool to act as a salt bridge.
  4. Insert each end of U-tube into the beakers.
  5. Connect copper and zinc to the voltmeter using crocodile clips.
  6. Record the EMF reading and sign.

Cell Notation:
Zn(s)|Zn2+(aq)||Cu2+(aq)|Cu(s)

Part 2: Measuring Comparative Electrode Potentials

Aim: To compare the electrode potential of various metals against a copper reference electrode.

Apparatus and Method Summary

AQA A-Level Chemistry comparative electrode potential setup using copper as reference electrode and other metals pressed against salt-soaked filter paper.
  1. Clean a piece of copper foil and connect it to the positive terminal of the voltmeter.
  2. Moisten filter paper with NaCl(aq) and place on the copper.
  3. Connect another metal to the negative terminal and press against the paper.
  4. Record the EMF and sign.
  5. Repeat with different metals (e.g. Ag, Fe, Mg) and tabulate results.
  6. Write conventional cell representations and identify the cell with the largest EMF.

Safety Notes