Some Gases (Tenset) 📚
B. Very Short Questions
11. Where is carbon dioxide found in nature?
→ Carbon dioxide is present at the lower level of the atmosphere and occurs in deep wells, mines, caves, etc. ⛰️
12. Write one physical property of carbon dioxide gas.
→ It is heavier than air. ⬇️
(Note: “It is an acidic gas” is a chemical property.)
13. Write the molecular formula of Ammonia.
→ NH₃
14. Which property of carbon dioxide helps to extinguish fire?
→ Carbon dioxide neither burns nor supports combustion, which helps to extinguish fire. 🔥
15. Ammonia gas cannot be collected in an erect gas jar. Why?
→ Ammonia is lighter than air (molecular weight 17 amu). If collected in an erect gas jar, it can escape easily. ⬆️
16. In which layer is the ozone layer found?
→ The ozone layer is found in the stratosphere layer of the atmosphere. ☁️
17. What is an ozone hole?
→ The ozone hole is the thinning of the ozone layer in the atmosphere that allows harmful UV rays to reach the Earth’s surface. ☀️
18. What happens when ammonia gas is passed into water containing a few drops of phenolphthalein solution?
→ The solution turns pink because ammonia dissolves in water to form ammonium hydroxide, which is basic. Phenolphthalein turns pink in a basic solution.
NH₃ + H₂O → NH₄OH
19. Name any two greenhouse gases.
→ Methane, Carbon dioxide, Chlorofluorocarbons, Ozone, Nitrous oxide (N₂O)
20. What is an artificial greenhouse?
→ An artificial greenhouse is a structure covered with polyethylene (plastic) or glass that traps solar rays inside. 🏠
— Page 1 —
21. Write any two effects of acid rain.
→ Acid rain:
Causes respiratory problems, skin and eye irritation in humans.
Kills aquatic and amphibian animals.
Increases soil acidity and decreases fertility.
22. Write one effect of ozone layer depletion.
→ It causes global warming, leading to natural disasters such as rising sea levels and irregular water cycles. It also causes respiratory problems and severe stress.
23. Why is it dangerous to clean a well that has remained closed for a long time?
→ A well closed for a long time may have a high concentration of carbon dioxide. Since CO₂ is heavier than air and can displace oxygen, it is dangerous and suffocating to enter. ⚠️
24. Write the uses of carbon dioxide.
→ Uses of carbon dioxide:
Used in making soft drinks and hard drinks like soda water, Coca-Cola, beer, etc.
Used by green plants during photosynthesis. 🌱
Used in fire extinguishers.
Used in the manufacture of fertilizers like urea and washing soda.
25. Which gas is obtained by reacting slaked lime and ammonium chloride?
→ Ammonia gas is obtained by reacting slaked lime and ammonium chloride.
26. Name two chemicals required to prepare CO₂.
→ Calcium carbonate (CaCO₃) and dilute hydrochloric acid (HCl).
27. Which gas is used to take out blueprints?
→ Ammonia gas is used to take out blueprints. 📐
28. Why is moist red litmus paper used for testing ammonia gas?
→ Ammonia is basic in nature. It turns moist red litmus paper blue, so moist red litmus paper is used for testing ammonia gas.
29. Carbon dioxide is not collected over water. Why?
→ Carbon dioxide is not collected over water because it is soluble in water and forms carbonic acid (H₂CO₃). This would result in loss of gas.
CO₂ + H₂O → H₂CO₃
— Page 2 —
30. A moist red litmus paper is used for testing ammonia gas. Why?
→ Ammonia is basic in nature. When it comes in contact with moist red litmus paper, it dissolves in the water and forms NH₄OH (ammonium hydroxide), which turns the red litmus paper blue, confirming the presence of ammonia.
31. How is carbon dioxide gas prepared in the laboratory?
→ Carbon dioxide is prepared in the laboratory by reacting calcium carbonate with dilute hydrochloric acid. ⚗️
CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O
32. Draw a neat and labeled diagram showing the laboratory preparation of ammonia gas.
→ The diagram should show:
A hard glass test tube inclined downward
Mixture of Ca(OH)₂ and NH₄Cl inside the tube
Burner heating the mixture
Delivery tube leading to gas jar
Lime tower with quicklime (CaO) to dry the gas
Gas jar inverted (upward displacement of air) ⬆️
33. Write any two uses of ammonia gas.
→ Uses of ammonia gas:
Used in refrigerators as a cooling agent instead of CFCs. ❄️
Used for the industrial preparation of plastics, washing soda, etc.
Used to make blueprints of maps, lands, buildings, etc.
Used to make ammonium salts for medicines.
34. How is urea prepared from ammonia gas?
→ Urea is prepared by reacting ammonia and carbon dioxide at about 150°C and under high pressure (about 30 atm).
2NH₃ + CO₂ →[150°C, 30 atm] (NH₂)₂CO + H₂O
35. In the given figure of preparing CO₂, how do you find out whether the gas jar is full or not? What will happen if the end ‘A’ of the delivery tube is dipped into the liquid in the bowl?
→ To check if the gas jar is full:
Bring a burning matchstick near the mouth of the jar. If it extinguishes, the jar is full of CO₂. 🔥
Alternatively, moist blue litmus paper turns red in the presence of CO₂.
→ If the end of the delivery tube is dipped into the liquid, CO₂ gas cannot be collected and will escape. Therefore, the delivery tube should not be dipped into the solution.
— Page 3 —
38. Write the differences between carbon dioxide and ammonia gas.
→ Carbon dioxide:
Made up of one carbon atom and two oxygen atoms.
Acidic in nature.
Heavier than air. ⬇️
→ Ammonia gas:
Made up of one nitrogen atom and three hydrogen atoms.
Basic in nature.
Has a strong pungent smell.
Lighter than air. ⬆️
39. Which gas is collected in the laboratory by downward displacement of air? Why?
→ Carbon dioxide is collected by downward displacement of air because it is heavier than air.
40. What happens when a burning magnesium ribbon is inserted inside a gas jar filled with carbon dioxide gas?
→ The burning magnesium ribbon continues to burn with a dazzling bright light and produces white ash of magnesium oxide and black particles of carbon. ✨
2Mg + CO₂ → 2MgO + C
43. Write two causative factors of ozone layer depletion.
→ Causes of ozone layer depletion:
Burning of fossil fuels, petrochemicals, wood, coal, etc.
Increase of greenhouse gases like CO₂, CH₄, CFCs, etc.
44. Write down the effects of acid rain.
→ Effects of acid rain:
Causes respiratory problems, skin and eye irritation.
Kills aquatic and amphibian animals.
Increases soil acidity and decreases fertility. 🌾
45. Which gases are produced when ammonium carbonate is heated in a hard-glass test tube?
→ Ammonia gas, carbon dioxide, and water vapor are produced.
(NH₄)₂CO₃ → 2NH₃ + CO₂ + H₂O
— Page 4 —
Section D: Long Questions
47(a). What happens when carbon dioxide gas is passed through lime water for a short time? Write with a balanced chemical equation.
→ When CO₂ is passed through lime water (calcium hydroxide) for a short time, it turns milky white due to the formation of insoluble calcium carbonate. 🥛
CO₂ + Ca(OH)₂ → CaCO₃ + H₂O
48. Draw a diagram of the laboratory preparation of ammonia gas and label it.
→ Diagram description:
Hard glass test tube inclined downward
Mixture of Ca(OH)₂ and NH₄Cl
Burner below the test tube
Delivery tube leading to lime tower
Lime tower with quicklime (CaO)
Gas jar inverted over the delivery tube ⚗️
49. How is ammonia gas prepared in the laboratory? Write the chemical equation.
→ Ammonia gas is prepared by heating a mixture of calcium hydroxide and ammonium chloride in a 1:2 molar ratio.
2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃
50. Answer the following questions based on the preparation of ammonia gas:
a) Write the balanced chemical reaction.
2NH₄Cl + Ca(OH)₂ → CaCl₂ + 2H₂O + 2NH₃
b) Why is the mouth of the hard glass test tube inclined downward?
→ To prevent condensed steam from flowing back into the hot part of the tube, which could crack it. 💧
c) Why cannot ammonia gas be collected over water?
→ Ammonia is highly soluble in water and forms ammonium hydroxide (NH₄OH).
d) Which litmus paper is used to confirm ammonia gas?
→ Red litmus paper turns blue in the presence of ammonia, confirming its basic nature.
— Page 5 —
51. Observe the diagram and answer:
i) Which gas is prepared using the given apparatus? Write the balanced chemical reaction.
→ Carbon dioxide gas is prepared by reacting calcium carbonate with dilute hydrochloric acid.
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂
ii) Write one use of that gas.
→ It is used in fire extinguishers and in the preparation of fertilizers like urea. 🧯
⭐ Study Tips ⭐
Remember: CO₂ is heavier → collected downward ⬇️
Remember: NH₃ is lighter → collected upward ⬆️
Red litmus → Blue = Basic (Ammonia) 🔵
Blue litmus → Red = Acidic (CO₂) 🔴
Good Luck with Your Revision! 📝✨
— Page 6 —