UNIT 16: SOME GASES
Multiple Choice Question [1 mark each]
1. What is the percentage of carbon dioxide in the
atmosphere by volume?
a) 78.8 b)
21.8 c) 0.3 d)
0.03
2. The gas jar in the laboratory preparation of carbon
dioxide is erect because …………………
a) Carbon dioxide is lighter than air.
b) Carbon dioxide is heavier than air.
c) Carbon dioxide is soluble in water.
d) Carbon dioxide is insoluble in water.
3. When carbon dioxide react with water, it forms
………………..
a) Water gas b)
carbolic acid c)
Carbonic acid d)
glucose
4. Which of the correct molecular formula of urea?
a) NH3-CH2-NH3 b)
NH2-CO-NH2 c) CH3-NH3 d) None of
these
5. Why is Haber’s process carried out in an iron
container?
a) To create 200-600 atmospheric pressure.
b) Iron can withstand 5000C temperature.
c) Iron container is rigid and strong.
d) Iron increases the rate of the combination of
nitrogen and hydrogen.
6. Which of the following is responsible for greenhouse
effect?
a) water vapour b)
nitrogen c) oxygen d)
Sulphur dioxide
7. Hard glass test tube is slanted during the laboratory
preparation of ammonia gas. Why?
a) To balance the centre of gravity so that the hard
glass test tube won’t fall.
b) To maintain uniform heating of reaction.
c) To avoid falling of condensed water-droplets on the
reactants.
d) To align the hard glass test tube with the delivery
tube.
8. How is carbon dioxide manufactured?
a) dissolving limestone in acid b) heating limestone in the furnace
c) burning coal in excessive oxygen d) burning coal in minimum
oxygen
9. At what temperature does ammonia boil?
a) -780C b)
00C c)
-250C d) -33.40C
10. At what temperature does CO2 change into dry ice?
a) -780C b)
00C c)
-250C d) -33.40C
11. Which of the condition is not required for the
manufacture of ammonia gas by Haber’s process?
a) temperature of 5000C b)
Pressure of 250 atmosphere
c) Presence of MnO2 d) Powdered Fe and Mo
12. Which of the following is used for extinguishing fire?
a) Carbon dioxide b)
Nitrogen c) Oxygen d)
Ammonia
13. The aqueous solution of gas that turns red litmus
paper to blue is
a) Carbon dioxide b)
Nitrogen c) Ammonia d)
Oxygen
14. Carbon dioxide is …………….. in nature.
a) Acidic b)
Basic c)
Neutral d) None of these
15. Carbon dioxide reacts with ammonia to produce …………….
a) Uric acid b)
Urea c)
Phosphate d) Sodium hydroxide
16. What does Carbon dioxide form after dissolving in
water?
a) Carbonyl sulphate b)
Carbonic acid c)
Carbon monoxide d) None of the above
17. What is colour of the carbon dioxide?
a) Blue b)
Yellow c)
Cololurless d) None of
these
18. Sodium hydrogren carbonate when added to acetic acid
evolves a gas. Which of the following statement is true about the evolved gas?
a) It turns lime milky white.
b) It extinguishes a burning sphincter.
c) It dissolves in the solution of sodium hydroxide.
d) It has a pungent odour.
a) i and ii b)
i, ii and iii c) ii, iii and
iv d)
i and iv
19. Which gas is manufactured by Haber’s process?
a) Carbon dioxide b)
Nitrogen c) Ammonia d)
Hydrogen
20. Ammonia dissolves in water to form ……………
a) Ammonium Chloride b)
Ammonium sulphate c) Ammonium
hydroxide
d) Ammonium nitrate
21. Ammonium is used for which of the mentioned processes?
a) Manufacture of nitrogen fertilizers.
22. b) Manufacture of nitric acid.
c) Manufacture of nitrogen chemical compounds.
d) All of the above.
23. Which of the mentioned statements regarding the
solubility of ammonia is true?
a) Insoluble in water.
b) Highly soluble in water.
c) Soluble in chloroform.
d) Highly soluble in water and soluble in chloroform.
24. Which of the mentioned statements regarding the
solubility of ammonia is true?
a) Insoluble in water.
b) Highly soluble in water
c) Soluble in chloroform
d) Highly soluble in water and soluble in Chloroform.
25. What is the catalyst used in manufacture of ammonia by
Haber’s process?
a) Fe b)
Mo c) Si d) Aluminium
26. Ammonia gas is collected by
a) Upward displacement of water.
b) Upward displacement of air.
c) Upward displacement of water.
d) Downward displacement of air.
27. In what ratio should ammonium chloride and calcium
hydroxide be mixed for the laboratory preparation of ammonia gas?
a) 3:1 b)
2:3 c) 1:2 d) 2:1
28. Greenhouse gases present in a very high quantity is
a) ethane b)
Carbon dioxide c) propane d)
Methane
29. Gas molecules absorbing thermal radiation and present
in large quantity to change the climate system is known as
30. a) Ozone gases b)
beta radiation c) alpha radiation d) greenhouse gases
31. Which green house gas is not produced naturally?
32. a) CFCs b)
Methane c) Carbon dioxide d) Nitrous oxide
33. The word acid rain was coined in ……………
34. a) 1853 b)
1852 c) 1851 d)
1850
35. Who coined the term acid rain?
36. a) Christer Ralph b)
Elmer Joseph Cklark c) Ernest
Flower d) Robert Angus Smith
37. The main cause of acid rain is …………………
38. a) Soil pollution b)
Water pollution c) Air pollution d) All of these
39. Acid rain cause
damage to ………….
40. a) big sculpture and marble construction
41. b) flora and fauna
42. c) growth of trees
43. d) All of the above
Answer:
1(d), 2(b), 3(c), 4(b), 5(d), 6(a), 7(c), 8(b), 9(d), 10(a), 11(c)
Very Short Answer Question [1 mark each]
1. Write down the molecular formula and molecular weight of carbon dioxide.
The molecular formula and molecular weight of carbon dioxide is CO2 and 44 amu respectively.
2. What happens when carbon dioxide is cooled to -780C?
When carbon dioxide is cooled to -780C, it changes into ice called dry ice.
3. Write down the molecular formula and molecular weight of ammonia.
The molecular formula and molecular weight of ammonia are NH3 and 17 amu respectively.
4. Which gas is obtained by reacting slaked lime and ammonium chloride?
5. Ammonia gas is obtained by reacting slaked lime and ammonium chloride.
6. Name two chemicals required for the preparation of Carbon dioxide gas in the laboratory.
Two chemicals required for the preparation of carbon dioxide gas in the laboratory are dilute hydrochloric acid and and calcium carbonate.
7. Name the chemical that are required to prepare ammonia gas in laboratory with their ratio.
Ammonium chloride and calcium hydroxide are the two chemicals required to prepare ammonia gas in the laboratory. It is taken in the ratio 2:1
8. Which chemical compound is kept in lime tower?
Calcium oxide is kept in lime tower.
9. Name two greenhouse gases.
Two green house gases are carbon dioxide and methane.
10. What is an artificial house made of glass to trap heat called?
An artificial house made of glass to trap heat is called a greenhouse.
11. Name two industrial gases.
Two industrial gases are oxygen and nitrogen.
12. Which gas is used as a coolant in refrigerator?
Ammonia (NH₃) gas is commonly used as a coolant in refrigerators.
13. What is liquor ammonia?
Liquor ammonia is a solution of ammonia gas (NH₃) dissolved in water. It is also called ammonium hydroxide.
14. What is dry ice?
Dry ice is the solid form of carbon dioxide (CO₂).
15. Which two gases are formed when ammonium carbonate is heated?
When ammonium carbonate is heated, it decomposes to form ammonia (NH₃) and carbon dioxide (CO₂) gases (along with water vapor).
16. Which gas is used to produce blueprint of map?
Ammonia gas (NH₃) is used to produce blueprints of maps (in the diazotype or blueprinting process).
17. Name two chemicals required to prepare CO2 in a laboratory.
Two chemicals required to prepare CO2 in a laboratory are: lime stone (Calcium carbonate ) and (Dilute hydrochloric acid)
18. State the laboratory preparation principle of CO2 gas.
The laboratory preparation principle of CO2 gas is: Carbon dioxide is prepared in the laboratory by treating dilute Hydrochloric acid on marble chips (Calcium carbonate).
19. How does carbon dioxide help in extinguishing fire?
Carbon dioxide extinguishes fires by displacing oxygen (as it is denser than air) and cooling the fuel through rapid expansion
20. Write the chemical formula of lime water.
The Chemical formula of lime water is Ca(OH)2.
21. Which gas is obtained by reacting slaked lime with ammonium chloride?
Ammonia gas is obtained by reacting slaked lime with ammonium chloride.
Short Answer Questions [2 marks each]
1. Where is carbon dioxide found in nature? What is its source?
Ans: Carbon dioxide (CO₂) is naturally found in the atmosphere, oceans, groundwater, lakes, ice caps, and seawater, originating from sources like volcanic outgassing, decomposing organic matter, wildfires, and respiration from organisms.
2. What happens when burning magnesium ribbon is inserted in the gas jar containing carbon dioxide? Write the chemical equation.
Ans: When a burning magnesium ribbon is inserted into a CO₂-filled gas jar, a vigorous reaction occurs, producing magnesium oxide (MgO) and carbon (C). The chemical equation is:
2Mg+CO2→2MgO+C
3. What will happen to the life if the earth stops working as a natural greenhouse?
Ans: If Earth lost its natural greenhouse effect, temperatures would drop, rendering the planet inhospitable. The greenhouse effect traps heat, maintaining a habitable climate. Without it, Earth’s average temperature would drop below freezing, disrupting ecosystems and making liquid water scarce
4. Why is carbon dioxide not used to fill balloons?
Ans: CO₂ is not used to fill balloons because it is denser than air, causing balloons to sink. Lighter gases like helium or hydrogen are preferred for buoyancy
5. How is ammonium sulphate prepared from ammonia? Write with a chemical reaction.
Ans: Ammonium sulfate is prepared by reacting ammonia (NH₃) with sulfuric acid (H₂SO₄):
2NH3+H2SO4→(NH4)2SO4
6. Write the balanced chemical equation for the laboratory preparation of carbon dioxide gas.
Ans: The equation is: CaCO3 (s)+2HCl(aq)→CaCl2 (aq)+H2O(l)+CO2 (g).
7. List the apparatus required for the laboratory preparation of carbon dioxide.
Ans: The required apparatus includes a Woulfe's bottle, gas jar, thistle funnel, delivery tube, rubber cork, and test tubes.
8. Why is carbon dioxide gas collected by the upward displacement of air?
Ans: It is collected this way because carbon dioxide is 1.5 times heavier than air.
9. State two precautions to be taken during the laboratory preparation of CO2
Ans: The end of the delivery tube should not be dipped into the acid, while the end of the thistle funnel must be dipped into the acid.
10. How can you test for the presence of carbon dioxide using a matchstick?
Ans: A burning matchstick brought near the mouth of the jar will extinguish because CO2 is neither combustible nor a supporter of combustion.
11. What observation is made when CO2 is passed through lime water for a short time?
Ans: The lime water turns milky white due to the formation of insoluble calcium carbonate (CaCO3)
12. Why does the milky color of lime water disappear when carbon dioxide is passed for a long time?
Ans: The milkiness disappears because the insoluble calcium carbonate reacts further to form soluble calcium bicarbonate [Ca(HCO3)2 .
13. Mention two physical properties of carbon dioxide gas.
Ans: It is a colourless and odourless gas that is slightly soluble in water.
14. What is dry ice and what is one of its primary uses?
Ans: Dry ice is solid carbon dioxide formed at temperatures below −78 ∘ C, and it is used to preserve fruits and vegetables at low temperatures.
15. Name two industrial chemicals manufactured using carbon dioxide.
Ans: Carbon dioxide is used to manufacture urea (NH2CONH2) and washing soda (Na2CO3).
16. Explain the chemical reason why CO2 is effective in fire extinguishers.
Ans: It forms a thick blanket over the fire that cuts off the oxygen supply, as it is heavier than air and does not support combustion.
17. Write the balanced chemical equation for the laboratory preparation of ammonia gas.
Ans: The balanced chemical equation for the laboratory preparation of ammonia gas is:
2NH4Cl(s)+Ca(OH)2 (s)→CaCl2 (s)+2H2O(l)+2NH 3 (g).
18. Why is ammonia gas collected by the downward displacement of air?
Ans: Ammonia is collected by the downward displacement of air because it is lighter than air and highly soluble in water.
19. What is the purpose of the lime tower in the laboratory preparation of ammonia?
Ans: The lime tower, filled with calcium oxide (CaO), is used to absorb moisture and obtain dry ammonia gas.
20. Why is the hard glass test tube kept slightly inclined downward during ammonia gas preparation?
Answer: Hard glass test tube is kept slightly inclined downwards during ammonia gas preparation to prevent water vapour produced during the process from trickling back into the hot tube and cracking it.
21. Describe the test for ammonia using concentrated hydrochloric acid.
Ans: When a glass rod dipped in concentrated HCl is brought near the gas jar, dense white fumes of ammonium chloride are produced.
22. What are the physical properties of ammonia regarding smell and solubility?
Ans: Ammonia has a strong and pungent odour like rotten eggs and is highly soluble in water.
23. What is the nature of ammonia gas according to its effect on litmus paper?
Ans: Ammonia is basic in nature, which causes it to change moist red litmus paper to blue8.
24. State two important uses of ammonia gas.
It is used to produce chemical fertilizers like urea and ammonium nitrate, and it serves as a cooling agent in refrigerators.
26. What does the ammonia fountain experiment prove?
Ans: This experiment proves that ammonia gas is highly soluble in water and possesses basic properties.
Long Answer Questions [4 marks each]
1. Write any four physical properties of carbon dioxide.
Four Physical Properties of Carbon
Dioxide (CO2) are:
a) It
is a colourless and odourless gas. •
b) It
is 1.5 times heavier than air.
c) It is slightly soluble in water,
and when dissolved, it forms carbonic acid, which has a sour taste
d) It can be liquefied at high
pressure and low temperature; when cooled below −78 ∘ C, it changes into a solid form
known as dry ice.
2. Write any four chemical properties of carbon dioxide.
Four Chemical Properties of Carbon
Dioxide (CO2 ) are as follows:
a) It is neither combustible nor a
supporter of combustion, which makes it useful for extinguishing fires.
b) It reacts with water to form a
weak acid called carbonic acid (H2CO3)2.
c) When passed through lime water,
it forms insoluble calcium carbonate, turning the water milky white. If passed
for a long time, the milkiness disappears as soluble calcium bicarbonate is
formed.
d) Green plants use carbon dioxide
as a raw material, reacting it with water in the presence of sunlight and
chlorophyll to prepare glucose and oxygen.
3. Write any four physical properties of ammonia.
Four Physical Properties of Ammonia
(NH3) include:
a) It is a colourless gas with a
strong, pungent odour similar to rotten eggs.
b) It is lighter than air.
c) It is highly soluble in water.
d) It is basic in nature, which
causes it to change moist red litmus paper to blue.
4. Write any four chemical properties of ammonia.
Four Chemical Properties of Ammonia
(NH3) include:
a) It reacts with water to form a
base called ammonium hydroxide (NH4OH).
b) Ammonia reacts with various acids
to form ammonium salts (for example, reacting with hydrochloric acid to produce
ammonium chloride).
c) At a high temperature of 1500∘ C and high pressure, it reacts with
carbon dioxide to form urea (NH2CONH2), a vital chemical
fertilizer.
d) Combustion: When ammonia burns in
an atmosphere of oxygen, it produces nitrogen gas and water.
5. Write the uses of carbon dioxide gas.
Uses of Carbon Dioxide Gas Carbon
dioxide has several important applications:
a) It is dissolved in soft drinks
under high pressure to provide a sour taste.
b) It is used in fire extinguishers
to put out fires by cutting off the oxygen supply.
c) It is used to manufacture dry
ice, which is essential for preserving fruits, vegetables, and meat at low
temperatures.
d) It is an industrial raw material
for producing chemicals like urea, washing soda, and baking soda.
e) In the medical field, it is mixed
with oxygen to create carbogen, which is used to treat patients with pneumonia
or respiratory issues.
6. Write the uses of ammonia gas.
Ammonia gas is utilized in the
following ways:
a) It is primarily used to produce
chemical fertilizers such as urea, ammonium sulphate, and ammonium nitrate.
b) It is used in the industrial
manufacture of nitric acid and plastics.
c) It serves as a cooling agent in
refrigerators7.
d) It is used to produce the
blueprints of maps7.
e) It acts as a cleansing agent used
to remove stains of grease or oil7.
7. Write the precaution that should be adopted during the
laboratory preparation of ammonia.
When preparing ammonia in a
laboratory, the following precautions must be observed:
a) The mouth of the hard glass test
tube must be slightly inclined downward. This prevents water vapour produced
during the reaction from trickling back into the hot part of the tube, which
could cause the glass to crack.
b) The apparatus must be made
airtight using a rubber cork.
c) The generated gas must be passed
through a lime tower filled with calcium oxide (CaO) to absorb moisture and
ensure the collected ammonia is dry.
d) The gas should be collected by
the downward displacement of air because it is lighter than air and highly
soluble in water (making collection over water impossible).
8. How is carbon dioxide prepared in the laboratory?
Write with the balanced chemical equation.
Carbon dioxide (CO2) is
prepared in the laboratory by the chemical reaction of limestone (calcium
carbonate, CaCO3) with dilute hydrochloric acid (HCl).
The balanced chemical equation for
this laboratory preparation is:
CaCO3 (s) + 2HCl(aq)→CaCl2
(aq) + H2O (l) + CO2 (g).
Laboratory Procedure
a) Pieces of limestone, marble, or
egg shells are placed into a Woulfe's bottle.
b) A thistle funnel and a delivery
tube are fitted into the openings of the bottle using rubber corks to make the
apparatus airtight.
c) Dilute hydrochloric acid is
poured through the thistle funnel until it completely covers the limestone and
the end of the thistle funnel is submerged within the acid layer. Reaction: Once the acid comes into contact
with the limestone, the chemical reaction begins, and carbon dioxide gas is
evolved.
It is collected in a gas jar through
the upward displacement of air
Testing: The presence of the gas can
be confirmed using a burning matchstick, which will extinguish because carbon
dioxide does not support combustion, or by passing it through lime water, which
will turn milky white.
9. Draw a neat labeled diagram showing laboratory
preparation of carbon dioxide gas in laboratory. Also describe the process.
A neat labeled diagram showing laboratory
preparation of carbon dioxide gas in laboratory is shown below:
The process of preparation
of the gas is
a) Pieces of limestone, marble, or
egg shells are placed into a Woulfe's bottle.
b) A thistle funnel and a delivery
tube are fitted into the openings of the bottle using rubber corks to make the
apparatus airtight.
c) Dilute hydrochloric acid is
poured through the thistle funnel until it completely covers the limestone and
the end of the thistle funnel is submerged within the acid layer.
Reaction: Once the acid comes into
contact with the limestone, the chemical reaction begins, and carbon dioxide
gas is evolved.
CaCO3 (s) + 2HCl(aq)→CaCl2
(aq) + H2O (l) + CO2 (g).
It is collected in a gas jar through
the upward displacement of air.
10. How is urea prepared from ammonia? Describe.
Urea is prepared industrially
through the chemical reaction between ammonia gas (NH3) and carbon
dioxide gas (CO2).
The preparation of urea requires
specific extreme conditions to facilitate the chemical change. The process
involves:
• Reactants: Ammonia and carbon
dioxide are used as the primary raw materials.
• Temperature: The reaction must
take place at a very high temperature of 1500∘C.
• Pressure: The gases must be
subjected to high pressure to react effectively.
•Result: Under these conditions,
the gases combine to form solid urea and liquid water.
The balanced chemical equation for
the preparation of urea is:
2NH3 (g) + CO2
(g) pressure/500∘C Ã NH2−CO−NH2
(s)+H2O (l).
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