Question 1: Define oxidation in terms of electron transfer.

Answer: Oxidation is the loss of electrons by a substance.

Question 2: Explain what is meant by reduction in chemical reactions.

Answer: Reduction is the gain of electrons by a substance.

Question 3: Describe the role of oxidation and reduction in the reactivity series of metals.

Answer: In the reactivity series, metals higher up tend to be oxidised more easily (lose electrons), while metals lower down are more easily reduced (gain electrons). Oxidation involves electron loss, and reduction involves electron gain, which determines how metals react with acids, water, or other substances.

Question 1: Calculate the number of electrons transferred when 5 mol of magnesium (Mg) atoms are oxidised to Mg²⁺ ions.

Answer: 10 mol of electrons (since each Mg atom loses 2 electrons, total electrons = 5 mol × 2 = 10 mol).

Question 2: A copper electrode gains 0.5 mol of electrons during electrolysis. How many moles of copper ions (Cu²⁺) are reduced?

Answer: 0.25 mol of Cu²⁺ ions (since 1 mol of Cu²⁺ gains 2 mol of electrons, so 0.5 mol electrons reduce 0.25 mol of Cu²⁺).

Question 1: Describe a basic experiment to demonstrate oxidation of zinc using dilute hydrochloric acid.

Answer: Place a strip of zinc metal into dilute hydrochloric acid. Observe the formation of hydrogen gas bubbles on the zinc surface. The zinc will undergo oxidation, losing electrons to form zinc ions, while hydrogen ions gain electrons to form hydrogen gas. Ensure safety by wearing gloves and goggles, and conducting the experiment in a well-ventilated area.

Question 2: Identify at least two variables that must be controlled during a reduction experiment involving metal ions in solution.

Answer: Concentration of metal ion solution and temperature must be controlled to ensure consistent reduction conditions.

Question 3: List safety precautions to consider when handling reactive metals and acids in oxidation-reduction experiments.

Answer: Wear appropriate PPE such as gloves and goggles, work in a well-ventilated area, and handle acids with care to avoid spills and skin contact.

Question 1: A student records that when zinc reacts with copper sulphate solution, the blue colour of the solution fades, and a layer of zinc metal forms on the copper electrode. Explain the oxidation and reduction processes occurring in this reaction.

Answer: Zinc atoms lose electrons and are oxidised to Zn²⁺ ions, which enter the solution. Copper ions in the solution gain electrons and are reduced to copper metal, depositing onto the electrode. The overall process involves zinc oxidation and copper reduction, demonstrating a redox reaction.

Question 2: In a reactivity series test, a metal that readily oxidises in air is likely to be:

Answer: B) Sodium

Question 1: Explain how the process of galvanising protects iron from rusting.

Answer: Galvanising involves coating iron or steel with a layer of zinc. Zinc acts as a sacrificial anode, oxidising more readily than iron. When the zinc layer is scratched or damaged, zinc still corrodes preferentially, protecting the underlying iron from rusting by reduction of oxygen and water at the zinc surface.

Question 2: Identify a modern technology that relies on redox reactions and describe its function briefly.

Answer: Fuel cells use redox reactions where hydrogen is oxidised to produce electricity, water, and heat, providing a clean energy source for vehicles and power generation.