Chemical Properties of Metals - UNSOLVED PRACTICE SET

Q7. Write balanced chemical equations for the reaction of: (i) Sodium with oxygen, (ii) Calcium with water, (iii) Zinc with dilute sulphuric acid.

Q8. Why do metals generally form basic oxides while non-metals form acidic oxides? Explain with examples.

Q9. Your mother stores leftover curry in an aluminium container. After a few hours, she notices a grey-black coating on the inside. Explain the chemical reaction that has occurred and why aluminium containers are not ideal for storing acidic foods.

Q10. What is an amphoteric oxide? Give two examples and write chemical equations showing their reaction with both acid and base.

Q11. Why does iron react with steam but not with cold water? Write the balanced chemical equation for the reaction of iron with steam.

Q12. Why does copper not displace hydrogen from dilute acids? What happens when copper is heated with concentrated sulphuric acid?

Q13. Describe the chemical properties of metals. Explain how metals react with: (i) oxygen, (ii) water, (iii) dilute acids, and (iv) other metal salts. Write balanced chemical equations for each type of reaction. What is an amphoteric oxide? Give examples.

Q14. A student performs experiments with four metals: sodium, magnesium, zinc, and copper.

(a) Describe what happens when each metal is added to cold water. Write chemical equations where reactions occur.

(b) Describe what happens when each metal is heated in air. Write chemical equations.

(c) Describe what happens when each metal is added to dilute hydrochloric acid. Write chemical equations.

(d) Arrange the metals in order of decreasing reactivity based on these observations.

(e) Explain why copper does not react with dilute HCl but reacts with concentrated nitric acid.

Q15. "The chemical properties of metals determine their usefulness and their limitations in everyday applications." Discuss this statement by explaining: (i) why aluminium utensils should not be used to cook acidic foods, (ii) why iron pipes are galvanised before being used for water supply, (iii) why sodium and potassium are stored under kerosene, and (iv) why gold and platinum are used for making dental fillings and jewellery.

Q16. A chemistry teacher demonstrates the reaction of metals with acids in the laboratory:

Table

Metal Mass Used (g) Acid Used Volume of H₂ at STP (mL)

Mg 0.24 Dilute HCl 224

Al 0.27 Dilute HCl 336

Zn 0.65 Dilute HCl 224

Fe 0.56 Dilute H₂SO₄ 224

(a) Write balanced chemical equations for each reaction.

(b) Calculate the number of moles of hydrogen produced in each case. (1 mole gas at STP = 22.4 L)

(c) Verify whether the volume of H₂ produced is consistent with the stoichiometry of each reaction.

(d) Calculate the equivalent weight of each metal based on the hydrogen displaced.

(e) Which metal is the most reactive based on the mass required to produce the same volume of hydrogen?

Q17. A metal extraction company in India processes metal ores using chemical reactions.

(a) When iron oxide (Fe₂O₃) is reduced by carbon monoxide: Fe₂O₃ + 3CO → 2Fe + 3CO₂. If 160 kg of Fe₂O₃ is processed, calculate the mass of iron produced. (Molar masses: Fe₂O₃ = 160 g/mol, Fe = 56 g/mol)

(b) Calculate the volume of CO₂ produced at STP.

(c) Aluminium is extracted by electrolysis of Al₂O₃. If 102 kg of Al₂O₃ is electrolyzed, calculate the mass of aluminium obtained. (Molar masses: Al₂O₃ = 102 g/mol, Al = 27 g/mol)

(d) Why is aluminium extracted by electrolysis while iron is extracted by reduction with carbon?

(e) If the company produces 100 tonnes of iron per day, calculate the daily requirement of Fe₂O₃.

Q18. A farmer in rural India uses various metals for agricultural tools and storage.

(a) The farmer has an iron plough that weighs 50 kg. If it rusts and loses 5% of its iron mass annually, calculate the mass of rust (Fe₂O₃·3H₂O) formed in one year. (Molar masses: Fe = 56 g/mol, Fe₂O₃·3H₂O = 214 g/mol)

(b) The farmer stores water in a copper vessel. Explain the chemical reaction that occurs when water is stored in copper, and why copper vessels are considered beneficial for health in Ayurveda.

(c) The farmer uses zinc-coated (galvanized) iron buckets for carrying water. Write the chemical reaction that would occur if the zinc coating is damaged and iron is exposed.

(d) If the farmer needs to replace 10 kg of iron tools with aluminium tools, and aluminium costs ₹200 per kg while iron costs ₹50 per kg, calculate the additional cost. Why might the farmer still prefer aluminium despite the higher cost?

(e) The farmer applies slaked lime (Ca(OH)₂) to acidic soil. If the soil contains 0.1 moles of H⁺ ions per square metre, calculate the mass of Ca(OH)₂ needed to neutralize 1000 square metres of soil. (Molar mass of Ca(OH)₂ = 74 g/mol)