Ans: Carbon dioxide is prepared in the laboratory by the action of dilute hydrochloric acid on calcium carbonate.
2. Dilute sulphuric acid should not be used for the laboratory preparation of carbon dioxide gas. Why?
Ans: Dilute sulphuric acid should not be used for the laboratory preparation of carbon dioxide gas because calcium sulphate so formed being insoluble will cover the calcium carbonate and stops the reaction further.
3. Ammonia gas is collected in the gas jar by downward displacement of air. Why?
Ans: Ammonia gas is collected in the gas jar by downward displacement of air because it is lighter than air and highly soluble in water.
4. Draw a neat and labeled diagram showing laboratory preparation of ammonia gas. Also write the balanced chemical reaction of that gas formed.
Ans:
In the laboratory, ammonia gas can be prepared by heating a mixture of ammonium chloride and calcium hydroxide in the ratio of 2:1 to yield calcium chloride, water and ammonia gas.
Ammonium Calcium Calcium Water Ammonia
chloride hydroxide chloride
5. Write any four chemical properties of ammonia gas.
Ans: Four chemical properties of ammonia gas are as following:
i. Ammonia is highly soluble in water to give ammonium hydroxide. The resultant solution of ammonium hydroxide, which is basic in nature.
NH3 + H2O → NH4OH
Ammonia Water Ammonium hydroxide
ii. Since ammonia is basic gas it reacts gas so it reacts with acid to give salt. For example, ammonia gives ammonium chloride with hydrochloric acid.
NH3 + HCl → NH4Cl
Ammonia Hydrochloric Ammonium
acid chloride
iii. Ammonia reacts with carbon dioxide at 15000C to give urea.
2NH3 + CO2 → NH2CONH2 + H2O
Ammonia Carbon dioxide Urea Water
iv. Ammonia is a non-combustible gas and it does not support combustion but it burns in oxygen to give nitrogen and water.
4NH3 + 3O2 → 6H2O
Ammonia Oxygen Water
6. What is ammonia?
Ans: Ammonia is a compound made up of nitrogen and hydrogen.
7. Ammonia gas cannot be collected by downward displacement of water. Why?
Ans: Ammonia gas cannot be collected by downward displacement of water because ammonia gas is highly soluble in water.
8. What happens when a glass rod dipped in conc. HCl is introduced in a jar containing ammonia gas?
Ans: When a glass rod dipped in conc. HCl is introduced in a jar containing ammonia gas, it produces white dense fumes of ammonium chloride.
9. What happens when ammonia gas is dissolved in water?
Ans: When ammonia gas is dissolved in water, ammonium hydroxide is formed.
10. What is slaked lime?
Ans: A white alkaline substance consisting of calcium hydroxide, made by adding water to quick lime is called slaked lime.
11. How is carbon dioxide prepared in the laboratory?
Ans: Carbon dioxide is prepared in the laboratory by the action of dilute hydrochloric acid on calcium carbonate.
12. Dilute sulphuric acid should not be used for the laboratory preparation of carbon dioxide gas. Why?
Ans: Dilute sulphuric acid should not be used for the laboratory preparation of carbon dioxide gas because calcium sulphate so formed being insoluble will cover the calcium carbonate and stops the reaction further.
13. What happens when carbon dioxide gas is dissolved in water?
Ans: When carbon dioxide gas is dissolved in water, carbonic acid is formed.
14. What happens when carbon dioxide is passed through lime water?
Ans: When carbon dioxide is passed through lime water, lime water turns milky due to the formation of white suspension of insoluble calcium carbonate.
15. What is dry ice?
Ans: The solid form of carbon dioxide is called dry ice.
16. What happens when carbon dioxide is continuously passed through lime water?
Ans: When carbon dioxide is continuously passed through lime water, the milky solution becomes clear due to the formation of soluble calcium bicarbonate.
17. What happens when the clear solution of calcium bicarbonate is boiled?
Ans: When the clear solution of calcium bicarbonate is boiled, calcium bicarbonate decomposes into calcium carbonate, water and carbon dioxide and the milkiness reappears due to the formation of calcium carbonate.
18. Carbon dioxide solution has acidic nature. Why?
Ans: Carbon dioxide solution has acidic nature because when carbon dioxide is dissolved in water, it forms carbonic acid which turns blue litmus paper into red.
19. Why carbon dioxide gas is collected in a gas jar by upward displacement of air?
Ans: Carbon dioxide gas is collected in a gas jar by upward displacement of air because carbon dioxide gas is heavier than air.
20. Why is carbon dioxide gas not collected in a gas jar by displacement of water?
Ans: Carbon dioxide gas is not collected in a gas jar by displacement of water because carbon dioxide gas is soluble in water.
21. Carbon dioxide gas is used to extinguish the fire. Why?
Ans: Carbon dioxide gas is used to extinguish the fire because it is neither combustible nor helps in combustion and being heavier than air it settles down on the burning surface and forms a layer cutting off the supply of oxygen to fire.
22. What is lime water?
Ans: Saturated solution of slaked lime in water is called lime water.
23. What is carbonation?
Ans: Carbonation is the phenomenon in which carbon dioxide gas is suspended in liquid, creating small bubbles.
24. What happens when ammonia reacts with carbon dioxide gas at 1500oC under low pressure?
Ans: When ammonia reacts with carbon dioxide gas at 1500oC under low pressure, urea, a nitrogenous fertilizer is produced.
25. What happens in each of the given conditions? Write the chemical equations.
i. Carbon dioxide is passed into lime water for a while.
ii. Carbon dioxide is passed into lime water for a long time.
iii. Carbon dioxide dissolves in water.
iv. Calcium bicarbonate is heated.
Ans: ii. Carbon dioxide is passed into lime water for a long time.
iii. Carbon dioxide dissolves in water.
iv. Calcium bicarbonate is heated.
i. When carbon dioxide is passed into the lime water for a while, it turns lime-water into milky white due to the formation of insoluble calcium carbonate.
CO2 + Ca(OH)2 → CaCO3 + H2O
Carbon Dioxide Lime water Calcium carbonate Water
ii. When carbon dioxide is passed into lime water for a long time, it produces soluble bicarbonate. As a result of this, the milky white colour disappears.
CaCO3 + H2O + CO2 → Ca(HCO3)2 (Calcium bicarbonate)
iii. Carbon dioxide gives carbonic acid (H2CO3) when it is dissolved in water.
CO2 + H2O → H2CO3
iv. When calcium bicarbonate is heated, calcium carbonate, carbon dioxide and water are formed.
Ca(HCO3)2 → CaCO3 + C02 + H20
26. What is Haber’s process?
Ans: Haber’s process is the commercial method of producing ammonia in which a mixture of nitrogen and hydrogen (1:3) is heated at a temperature of 500oC under 200-600 atmospheric pressure in the presence of iron as catalyst and molybdenum as promoter.