Unit 16: Gases
Complete Exercise Solutions — Class 10 Science & Technology
A. Multiple Choice Questions
1. Which property of CO₂ makes it suitable for use in fire extinguishers?
2. When carbon dioxide dissolves in water, which of the following compounds is formed?
3. What is A in the following chemical equation?
CaCO₃ + 2HCl → A + H₂O + CO₂
CaCO₃ + 2HCl → A + H₂O + CO₂
4. What does the increased concentration of CO₂ in the atmosphere mainly responsible for?
5. Dry ice is the solid form of carbon dioxide. Which property of dry ice makes it widely used for cooling?
6. Which of the following matches correctly between Column A and Column B?
Reference Mapping: a. CaCO₃ + dil HCl → Carbon dioxide (3) | b. CO₂ + H₂O → Carbonic acid (4) | c. NH₃ + HCl → Ammonium chloride (2) | d. Red litmus to blue → Ammonia (1).
7. What would be the product when ammonia gas burns in the presence of oxygen?
8. Carbon dioxide gas is collected by upward displacement of air. Which of the following is the best reason for it?
9. In which ratio by weight do we mix ammonium chloride and calcium hydroxide to prepare ammonia in the laboratory?
10. What does a layout covered with transparent plastic/glass indicate in standard sustainable crop protection farming?
B. Very Short Answer Type Questions
11. Write the chemical equation of the laboratory preparation of carbon dioxide gas.
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ ↑
12. What is the chemical nature of carbon dioxide gas?
It is acidic in nature (it turns moist blue litmus paper red).
13. The gas jar is kept erect during the laboratory preparation of carbon dioxide gas, why?
Because carbon dioxide gas is heavier than air, so it settles downward and replaces air upward.
14. How would you test for carbon dioxide gas? Give an example.
Pass the gas through lime water; it turns the lime water milky due to the formation of insoluble calcium carbonate (CaCO₃).
15. If you are given ammonium chloride and calcium hydroxide, which gas can be prepared from these chemicals?
Ammonia gas (NH₃).
16. Ammonia is basic in nature. How do you prove this?
Bring a moist red litmus paper near a gas jar filled with ammonia; it will immediately turn blue, proving its basic nature.
17. What is acid rain?
Acid rain is precipitation containing high levels of nitric and sulfuric acids caused by atmospheric pollutants like SO₂ and NOₓ.
18. What does uncontrolled high greenhouse emissions cause globally?
It causes Global Warming and rapid climate change.
19. What does an enclosed plastic shelter farming system indicate?
It indicates an Artificial Greenhouse setup.
20. What major balanced environmental action can be taken from our side to mitigate rising earth temperatures?
Large-scale afforestation (planting trees) and switching to clean, renewable energy alternatives.
C. Short Answer Type Questions
21. Write any two properties of carbon dioxide.
1. It is a colorless, odorless gas that is heavier than air.
2. It dissolves in water to produce weak carbonic acid (H₂CO₃).
2. It dissolves in water to produce weak carbonic acid (H₂CO₃).
22. Describe the apparatus setup for the laboratory preparation of carbon dioxide gas.
In a Woulfe's bottle, marble chips (CaCO₃) are placed. Dilute hydrochloric acid (HCl) is poured through a thistle funnel. The chemical reaction produces carbon dioxide gas, which passes through a delivery tube and is collected in an upright gas jar via upward displacement of air.
23. What are the common setup mistakes in an incorrect Ammonia lab preparation diagram?
1. The gas jar is kept upright (Ammonia is lighter than air and must be collected using an inverted jar).
2. The boiling hard-glass test tube is tilted upward (it must be slanted slightly downward towards its mouth to prevent condensed water droplets from cracking the hot tube).
2. The boiling hard-glass test tube is tilted upward (it must be slanted slightly downward towards its mouth to prevent condensed water droplets from cracking the hot tube).
24. A lime tower containing CaO is used to prepare ammonia in the laboratory. What would happen when the tower is not used?
If the lime tower is omitted, the collected ammonia gas will remain moist and mixed with water vapor. Quicklime (CaO) acts as an essential basic drying agent to absorb moisture.
25. Which two tests are done to confirm ammonia gas in the laboratory?
1. Litmus Test: It changes moist red litmus paper into blue.
2. HCl Dense Fume Test: A glass rod dipped in concentrated hydrochloric acid brought near the gas produces dense white fumes of ammonium chloride (NH₄Cl).
2. HCl Dense Fume Test: A glass rod dipped in concentrated hydrochloric acid brought near the gas produces dense white fumes of ammonium chloride (NH₄Cl).
26. A gas produced from coal purification (CO₂) is used with ammonia to manufacture nitrogenous urea fertilizer. Write the balanced chemical equation.
2NH₃ + CO₂ ⎯⎯High Temp & Pressure⎯→ NH₂CONH₂ (Urea) + H₂O
D. Long Answer Type Questions
27. Study the laboratory setup for Carbon Dioxide Gas and answer:
a. What is X? X represents the Thistle Funnel (or dilute HCl reactant being poured).
b. Major Mistake: Collecting the gas in an inverted jar or using a delivery tube that doesn't reach the bottom. Carbon dioxide must be collected in an erect gas jar because it is heavier than air.
c. Process: Place calcium carbonate pieces in the flask, pour dilute HCl through the thistle funnel, ensure the funnel tip is submerged under the acid solution, and collect the escaping gas via upward displacement of air.
b. Major Mistake: Collecting the gas in an inverted jar or using a delivery tube that doesn't reach the bottom. Carbon dioxide must be collected in an erect gas jar because it is heavier than air.
c. Process: Place calcium carbonate pieces in the flask, pour dilute HCl through the thistle funnel, ensure the funnel tip is submerged under the acid solution, and collect the escaping gas via upward displacement of air.
28. Write any four major effects of global warming.
1. Rapid melting of polar ice caps and Himalayan glaciers leading to rising sea levels.
2. Shifting ecosystems and loss of biodiversity due to temperature stress.
3. Increase in extreme, unpredictable weather hazards (severe droughts, sudden floods).
4. Decreased global agricultural productivity and crop yields.
2. Shifting ecosystems and loss of biodiversity due to temperature stress.
3. Increase in extreme, unpredictable weather hazards (severe droughts, sudden floods).
4. Decreased global agricultural productivity and crop yields.
29. What advantages can we get by using an artificial greenhouse? Explain.
• Off-season farming: Warm temperatures are trapped inside, allowing farmers to grow summer crops during winter.
• Extreme Weather Shielding: It protects fragile, valuable plants from strong storms, frost, and driving rain.
• Enhanced Plant Growth: It helps retain optimal humidity and warmth levels, maximizing yield.
• Extreme Weather Shielding: It protects fragile, valuable plants from strong storms, frost, and driving rain.
• Enhanced Plant Growth: It helps retain optimal humidity and warmth levels, maximizing yield.
30. Write any four chemical properties of ammonia gas.
1. Basic Property: Reacts with acids to produce ammonium salts: NH₃ + HCl → NH₄Cl
2. Reaction with Water: Readily dissolves to form ammonium hydroxide base: NH₃ + H₂O → NH₄OH
3. Combustion: Burns in oxygen with a greenish-yellow flame to produce nitrogen gas: 4NH₃ + 3O₂ → 2N₂ + 6H₂O
4. Urea Production: Reacts with CO₂ at high pressures to produce urea fertilizer.
2. Reaction with Water: Readily dissolves to form ammonium hydroxide base: NH₃ + H₂O → NH₄OH
3. Combustion: Burns in oxygen with a greenish-yellow flame to produce nitrogen gas: 4NH₃ + 3O₂ → 2N₂ + 6H₂O
4. Urea Production: Reacts with CO₂ at high pressures to produce urea fertilizer.
31. Find missing variables W, X, Y, and Z from the reaction data table.
| Reactants | Products | Solved Variable Value |
|---|---|---|
| 2Na + 2NH₃ | 2NaNH₂ + H₂ | W = NaNH₂ (Sodium amide) |
| CO₂ + 2NaOH | Na₂CO₃ + H₂O | X = NaOH (Sodium hydroxide) |
| 8NH₃(excess) + 3Cl₂ | 6NH₄Cl + N₂ | Y = N₂ (Nitrogen gas)* |
| 2Mg + CO₂ | 2MgO + C | Z = CO₂ (Carbon dioxide gas) |
*Note: Textbook equation specifies NH₄Cl as product which happens when Ammonia is in excess, hence Y is N₂ gas.
32. How do you draw the corrected laboratory preparation figure for Ammonia?
To correct the standard textbook mistake diagram for Ammonia gas preparation:
- Change the posture of the hard glass test tube containing the reactants to slant slightly downwards towards its mouth.
- Flip the collection gas jar completely upside down (inverted position) over the delivery tube line to correctly secure the gas via downward displacement of air.