Practicals

• What is the aim of the experiment described in the study material?

  To obtain dry crystals of copper sulphate.
• What is the first step in making salts using copper oxide and sulphuric acid?

  1. Take a base (e.g., powdered copper oxide).
  2. Mix with heated acid (e.g., concentrated sulphuric acid).
  3. This causes a neutralisation reaction that produces a salt solution (copper sulphate solution).
• How can you indicate that excess copper oxide has been added to the reaction?

  By observing unreacted powder at the bottom of the beaker.
• What is the purpose of using a filter funnel and filter paper in the process?

  • To separate the unreacted copper oxide from the copper sulphate solution.
  • The solution is filtered into a conical flask.
• What is the next step after filtering the solution into a conical flask?

  1. Pour the filtrate into an evaporating basin.
  2. Place the basin on a beaker of water over a tripod, gauze, and Bunsen burner.
  3. Heat gently to evaporate the water.
• What equipment is used to heat the evaporating basin?

  A Bunsen burner, tripod, and gauze.
• What is the purpose of heating the solution in the evaporating basin?

  To evaporate the water and obtain dry crystals of copper sulphate.
• What type of acid is used in the experiment?

  Concentrated sulphuric acid.
• What is the base used in the experiment?

  Powdered copper oxide.
• What is the overall process of making salts as described in the study material?

  1. Mix base with heated acid to produce a salt solution.
  2. Add excess base to ensure complete reaction.
  3. Filter the solution to remove unreacted base.
  4. Evaporate the solution to obtain dry crystals of salt.
• What is the aim of the temperature change experiment described?

  To use temperature change to determine the volume needed to neutralise.
• What is the independent variable in the experiment?

  The volume of alkali needed.
• What is the dependent variable in the experiment?

  The maximum temperature needed.
• What is the aim of electrolysis?

  To determine the products made when a current is passed through a salt solution.
• What is the setup for electrolysis?

  • Place carbon electrodes (inert) in a salt solution.
  • Ensure electrodes do not touch.
  • Connect to a battery or DC power supply.
  • Identify electrodes: negative electrode is the cathode, positive electrode is the anode.
• What ions are present in a sodium chloride solution during electrolysis?

  H⁺, OH⁻, Na⁺, and Cl⁻ ions.
• What happens if the metal is more reactive than hydrogen during electrolysis?

  The metal will stay in solution, and hydrogen will be reduced at the cathode to make H₂ gas.
• What occurs if the metal is less reactive than hydrogen during electrolysis?

  The metal will be reduced instead of hydrogen.
• What are the steps involved in the temperature change experiment?

  1. Measure out volumes of acid and alkali.
  2. Place them in a polystyrene cup with a lid and thermometer (optionally in a beaker for stability).
  3. Record the maximum temperature reached.
  4. Repeat with increasing volumes of alkali.
  5. Plot maximum temperatures against the volume of alkali.
  6. Identify where the two lines of best fit (LOBF) meet to find the volume of alkali needed to neutralise the acid.
• What happens to halide ions during electrolysis?

  Halide ions (Cl, Br, I) will be oxidized at the anode, producing Cl₂ gas.
• What is produced when chloride ions are oxidized at the anode?

  Chlorine gas (Cl₂).
• What is produced at the anode if the non-metal ion is not a halide?

  Oxygen gas (O₂) is produced at the anode.
• What happens to the maximum temperatures as the volume of alkali increases?

  The maximum temperatures will decrease once the alkali is in excess.
• What are the half-equations for the electrolysis of sodium chloride solution?

  • At the cathode: $2H^+$$(aq) +$$2e^- \rightarrow H_2(g)$
  • At the anode: $2Cl^-(aq) \rightarrow Cl_2(g) +$$2e^-$
• What remains in solution after the electrolysis of sodium chloride?

  Sodium hydroxide (NaOH) remains in solution.
• How does the reactivity of metals affect the products of electrolysis?

  • More reactive metals: remain in solution, hydrogen gas produced at cathode.
  • Less reactive metals: reduced at cathode instead of hydrogen.
• Why do maximum temperatures decrease when alkali is in excess?

  Because the same amount of energy is distributed through a greater volume.
• Where do you find the volume of alkali needed to neutralise the acid on the graph?

  Where the two lines of best fit (LOBF) meet.
• What controls should be maintained during the experiment?

  • Concentration of reactants
  • Initial temperature
• What type of cup is used in the experiment to measure temperature changes?

  A polystyrene cup.
• Why might a beaker be used in the experiment?

  For stability of the polystyrene cup.
• What does the graph of maximum temperature plotted against volume of alkali typically show?

  • A peak indicating the maximum temperature reached.
  • A decrease in temperature after the alkali is in excess.