Question 1: Define a displacement reaction in the context of chemical changes involving metals.

Answer: A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its compound in solution.

Question 2: Explain why aluminium does not displace iron from its salt solution, despite being more reactive than many other metals.

Answer: Aluminium does not displace iron because aluminium forms a protective oxide layer that prevents it from reacting further, despite its position in the reactivity series.

Question 3: Describe the mechanism of a typical displacement reaction between zinc and copper sulphate.

Answer: Zinc displaces copper from copper sulphate because zinc is more reactive. Zinc atoms lose electrons to form Zn²⁺ ions, which enter the solution, while copper ions gain electrons and deposit as copper metal on the zinc surface.

Question 4: Identify the metal in the reactivity series that can displace both magnesium and zinc from their salts.

Answer: Aluminium.

Question 5: Calculate the amount of zinc required to displace 0.5 mol of copper in a reaction. (Use the molar ratio 1:1, Zn : Cu).

Answer: 0.5 mol of zinc (since molar ratio is 1:1).

Question 6: In an experiment, a strip of magnesium is placed in dilute hydrochloric acid. Write the word equation for the reaction.

Answer: Magnesium + Hydrochloric acid → Magnesium chloride + Hydrogen gas

Question 7: Identify the variables involved in the practical experiment of placing a metal strip in salt solution to observe displacement.

Answer: Variables include the type of metal (independent), concentration of salt solution (controlled), temperature (controlled), and observation of the reaction (dependent).

Question 8: Describe the safety precautions necessary when performing displacement reactions involving acids and reactive metals.

Answer: Wear safety goggles and gloves, work in a well-ventilated area, handle acids carefully to avoid spills and burns, and dispose of chemicals according to safety guidelines.

Question 9: A solution contains dissolved zinc ions. Which metal (from copper, silver, platinum) can displace zinc, and why?

Answer: Copper and silver can displace zinc because they are more reactive than zinc in the reactivity series.

Question 10: Explain how displacement reactions are used in galvanising steel to prevent rusting.

Answer: Galvanising involves coating steel with a layer of zinc. When the steel is scratched, zinc reacts with oxygen and moisture in the environment, forming a protective layer of zinc oxide. Zinc also displaces any corrosion-causing substances, preventing rusting of the steel underneath, thus extending its lifespan.