Displacement Reactions - UNSOLVED PRACTICE SET

Q7. Define displacement reaction. Write the general equation for a displacement reaction where a metal A displaces metal B from its salt solution.

Q8. Write balanced chemical equations for the following displacement reactions:

(a) Zinc added to copper sulphate solution.

(b) Iron added to dilute sulphuric acid.

Q9. Your grandmother stores pickles in brass (copper-zinc alloy) containers. After some time, she notices a green coating on the inside. Explain the displacement reaction involved and why brass containers are not suitable for storing pickles.

Q10. Why can copper displace silver from silver nitrate solution, but cannot displace zinc from zinc sulphate solution? Explain using the reactivity series.

Q11. A student adds magnesium ribbon to a solution of iron sulphate. What colour change would she observe? Write the balanced chemical equation and identify the type of reaction.

Q12. Arrange the following metals in decreasing order of reactivity: K, Na, Ca, Mg, Al, Zn, Fe, Pb, Cu, Ag, Au. Which of these metals can displace hydrogen from dilute acids?

Q13. Define displacement reaction and explain it with reference to the reactivity series of metals. Describe the reaction between zinc and copper sulphate solution with observations. Why can a more reactive metal displace a less reactive metal from its compound? Give two more examples of displacement reactions.

Q14. A student performs three experiments:

Experiment 1: Places an iron nail in copper sulphate solution

Experiment 2: Places a copper wire in zinc sulphate solution

Experiment 3: Places a zinc strip in lead nitrate solution

(a) Predict the observations for each experiment.

(b) Write balanced chemical equations for the reactions that occur.

(c) Identify which experiments show displacement reactions and which do not.

(d) Explain your predictions using the reactivity series.

(e) What would happen if a silver coin is placed in copper sulphate solution? Give a reason.

Q15. "Displacement reactions have been used by humans for thousands of years, from ancient metal extraction to modern industrial processes." Discuss this statement by explaining: (i) how displacement reactions are used in the extraction of metals from their ores, (ii) the thermite reaction and its applications, (iii) how displacement reactions help in understanding the reactivity series, and (iv) their role in corrosion and preventive measures.

Q16. In a chemistry laboratory, a student performs displacement reactions with the following metals and solutions:

Table

Metal Solution Observation

Zinc CuSO₄ Blue colour fades, reddish-brown deposit

Copper ZnSO₄ No change

Iron CuSO₄ Blue colour fades, reddish-brown deposit

Silver CuSO₄ No change

(a) Write balanced chemical equations for the reactions that occur.

(b) If 6.5 g of zinc is added to excess copper sulphate solution, calculate the mass of copper displaced. (Atomic masses: Zn = 65, Cu = 63.5)

(c) If 5.6 g of iron is added to excess copper sulphate, calculate the mass of copper displaced. (Atomic mass: Fe = 56)

(d) Arrange the four metals (Zn, Cu, Fe, Ag) in order of decreasing reactivity based on these experiments.

(e) If the student wants to recover 31.75 g of copper by displacement, what mass of zinc should be used?

Q17. The thermite reaction is used to weld railway tracks:

Fe₂O₃ + 2Al → Al₂O₃ + 2Fe

(a) Is this a displacement reaction? Give a reason.

(b) If 160 kg of iron(III) oxide reacts with excess aluminium, calculate the mass of iron produced. (Molar masses: Fe₂O₃ = 160 g/mol, Fe = 56 g/mol)

(c) Calculate the mass of aluminium required for complete reaction. (Atomic mass: Al = 27)

(d) Why is this reaction called the thermite reaction? What is its practical application in railway track welding?

(e) In India, railway tracks are welded using this method in remote areas. Why is this method preferred over conventional welding?

Q18. A farmer has iron tools that he wants to protect from rusting. He learns that coating iron with zinc (galvanization) prevents rusting because zinc is more reactive than iron.

(a) If zinc coating is damaged and iron is exposed, will iron rust? Explain using the concept of displacement reactions.

(b) If the farmer has 100 kg of iron tools and wants to coat them with a 2% zinc layer by mass, calculate the mass of zinc needed.

(c) Write the balanced equation for the reaction of zinc with dilute hydrochloric acid.

(d) If 13 g of zinc reacts with excess HCl, calculate the volume of hydrogen gas produced at STP. (Molar masses: Zn = 65 g/mol, H₂ = 2 g/mol; 1 mole gas at STP = 22.4 L)

(e) Why is galvanization more effective than painting for protecting iron structures in coastal areas of India?