Important Compounds CaO Ca(OH)2 CaCO3 Plaster of Paris - UNSOLVED PRACTICE SET

Q7. Write the chemical equation for the slaking of lime. Why is this reaction exothermic? Mention one use of slaked lime in agriculture.

Q8. Explain why calcium carbonate (limestone) is used in the extraction of iron in blast furnaces. What role does it play?

Q9. Your school is being whitewashed using slaked lime. Explain the chemistry behind whitewashing — why does the wall appear white after some time, and what happens when CO₂ from air reacts with it?

Q10. Why is Plaster of Paris used for setting fractured bones in hospitals? What property makes it ideal for this purpose?

Q11. Write the chemical reactions involved in the manufacture of bleaching powder from slaked lime. Why is bleaching powder called "chloride of lime"?

Q12. Why is cement called a "hydraulic cement"? What is the role of gypsum (CaSO₄·2H₂O) in the manufacture of Portland cement?

Q13. Describe the preparation, properties, and uses of calcium oxide (quicklime). Include:

(a) Preparation from limestone by calcination

(b) Reaction with water (slaking) and its exothermic nature

(c) Reaction with carbon dioxide and acids

(d) Uses in steelmaking, manufacture of calcium carbide, and as a drying agent

Write balanced chemical equations for all reactions.

Q14. Discuss the preparation, properties, and uses of Plaster of Paris (POP). Include:

(a) Preparation from gypsum by controlled heating

(b) The setting process and formation of gypsum

(c) Why it is called "Plaster of Paris"

(d) Uses in surgery, making toys, decorative items, and false ceilings

(e) The chemistry behind its setting and hardening

Q15. Calcium compounds are the backbone of the Indian construction industry. Discuss:

(a) The role of limestone in cement manufacture and why India is one of the largest cement producers

(b) How slaked lime is traditionally used in Indian villages for whitewashing houses and disinfecting surfaces

(c) The environmental impact of limestone mining and cement production (CO₂ emissions)

(d) Sustainable alternatives being explored in green construction in India

Q16. In a lime kiln, 100 kg of pure calcium carbonate (CaCO₃) is heated strongly.

(a) Write the decomposition reaction.

(b) Calculate the mass of quicklime (CaO) produced.

(c) Calculate the volume of CO₂ evolved at STP.

[Given: Atomic masses: Ca = 40, C = 12, O = 16; Molar volume at STP = 22.4 L]

Q17. A hospital uses Plaster of Paris for setting a fractured bone. The doctor uses 50 g of Plaster of Paris (CaSO₄·½H₂O).

(a) Write the setting reaction when POP is mixed with water.

(b) Calculate the mass of gypsum (CaSO₄·2H₂O) formed when 50 g of POP sets completely.

(c) Calculate the mass of water required for complete setting.

[Given: Atomic masses: Ca = 40, S = 32, O = 16, H = 1]

Q18. A construction company in Jaipur needs to whitewash a building. They have 100 kg of quicklime (CaO).

(a) Calculate the mass of slaked lime (Ca(OH)₂) that can be produced from 100 kg of CaO.

(b) When this slaked lime is applied to walls, it reacts with atmospheric CO₂. Calculate the mass of CaCO₃ formed if all the slaked lime reacts completely.

(c) If the cost of quicklime is ₹ 8 per kg and the labour cost for whitewashing is ₹ 500, calculate the total cost for this project.

[Given: Atomic masses: Ca = 40, O = 16, H = 1, C = 12]