Reaction of Acids and Bases with Metals - UNSOLVED PRACTICE SET

Q7. Write balanced chemical equations for the reaction of: (i) Zinc with dilute sulphuric acid, (ii) Magnesium with dilute hydrochloric acid, (iii) Iron with dilute sulphuric acid.

Q8. Why does copper not react with dilute hydrochloric acid or dilute sulphuric acid? Under what conditions can copper react with acids?

Q9. Your father stores pickles in a glass jar, not in an aluminium container. Explain the chemical reaction that would occur if pickles (which contain acids) were stored in an aluminium container.

Q10. Why is sodium metal stored under kerosene oil? What would happen if sodium is exposed to air or water?

Q11. Write the balanced chemical equation for the reaction of aluminium with: (i) dilute hydrochloric acid, and (ii) sodium hydroxide solution. What does this tell you about the nature of aluminium?

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

Q13. Describe the reactions of metals with acids and bases. Write balanced chemical equations for the reactions of zinc, iron, aluminium, and sodium with dilute HCl and dilute NaOH (where applicable). Why do some metals react with both acids and bases? Explain the concept of amphoteric nature with reference to aluminium and zinc.

Q14. A student performs experiments by adding different metals to dilute hydrochloric acid:

Experiment 1: Magnesium ribbon — vigorous bubbling, metal dissolves

Experiment 2: Zinc granules — moderate bubbling, metal dissolves slowly

Experiment 3: Iron filings — slow bubbling, metal dissolves very slowly

Experiment 4: Copper turnings — no reaction

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

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

(c) Explain why copper does not react with dilute HCl.

(d) If the student collects the gas evolved in Experiment 1 and brings a burning splinter near it, what happens? Write the chemical equation.

(e) How would the observations change if concentrated sulphuric acid were used instead of dilute HCl?

Q15. "The reaction of metals with acids and bases is not just a laboratory curiosity — it has practical applications in our daily lives and industries." Discuss this statement by explaining: (i) how the reactivity of metals with acids helps in extracting metals from their ores, (ii) why aluminium utensils should not be used to store acidic foods, (iii) the use of sodium metal in street lamps and nuclear reactors, and (iv) the role of acid-metal reactions in the preparation of hydrogen gas for industrial use.

Q16. In a chemistry laboratory, students react different metals with acids and measure the volume of hydrogen gas produced:

Table

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

Mg 0.24 Dilute HCl 224

Zn 0.65 Dilute HCl 224

Fe 0.56 Dilute H₂SO₄ 224

Al 0.18 Dilute HCl 224

(a) Write balanced chemical equations for each reaction.

(b) Verify whether the volume of H₂ produced is consistent with the amount of metal used. (Atomic masses: Mg = 24, Zn = 65, Fe = 56, Al = 27; 1 mole gas at STP = 22.4 L)

(c) Calculate the number of moles of hydrogen produced in each case.

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

(e) If 1.2 g of magnesium is used, what volume of hydrogen would be produced at STP?

Q17. A hydrogen gas generator in a school laboratory uses zinc and dilute sulphuric acid:

Zn + H₂SO₄ → ZnSO₄ + H₂

(a) If 13 g of zinc is used, calculate the volume of hydrogen gas produced at STP. (Atomic mass of Zn = 65; 1 mole gas at STP = 22.4 L)

(b) If the acid used is 0.5 M H₂SO₄, what minimum volume of acid is needed to completely react with 13 g of zinc?

(c) The hydrogen gas collected is used to reduce copper oxide: H₂ + CuO → Cu + H₂O. If all the hydrogen produced is used, calculate the mass of copper obtained. (Atomic mass of Cu = 63.5)

(d) Why is hydrogen gas called a "clean fuel"? What are its advantages and disadvantages as a fuel for vehicles in India?

Q18. In India, sodium metal is produced by the electrolysis of molten sodium chloride (Downs process). Sodium is highly reactive and has many uses.

(a) Write the chemical equation for the reaction of sodium with water. Why is this reaction dangerous?

(b) If 2.3 g of sodium reacts with excess water, calculate the volume of hydrogen gas produced at STP. (Atomic mass of Na = 23)

(c) Calculate the mass of sodium hydroxide produced in the above reaction. (Molar mass of NaOH = 40 g/mol)

(d) Sodium vapour lamps are used for street lighting. Explain why sodium lamps produce yellow light and why they are preferred over ordinary bulbs for street lighting in India.

(e) Why is sodium metal transported in sealed containers filled with kerosene, and what would happen if the container leaked during transport?