Selina Concise Class 7 Chemistry Solution Chapter No. 7- ‘Air and Atmosphere’ For ICSE Board Students.
Exercise –I Solution:
1)
a)
Answer : Argon :
- Argon gas used in museum to protect and preserve the old documents and materials.
- Argon gas fill in light bulb to protect filament.
b)
Answer : Helium :
- Helium gas used in extremely low temperature to achieve superconductivity position.
- It is used to fill in balloons .
c)
Answer : Neon :
- It is used forlighting , for example neon lamp and advertising sign.
- It is used to make high voltage indicator ,
d)
Answer : Radon :
- It is used in to preparation of ointment for the treatment of cancer and other disease .
- It is used in radiation therapy in hospital.
e)
Answer : Krypton :
- Krypton gas used in high efficiency minor’s cap lamp.
- It is used in filling luminous tube.
f)
Answer : Xenon :
- It is used in high speed discharge tube for producing high speed flash of bluish light uses in quick photography.
- It is used in arc lamp in projector .
2)
a)
Answer : Nitrogen :
Nitrogen is essential component for animals and plants , Through this Nitrogen plants convert it into protein and animals get this protein from plants, protein is very important for plants and animals for their growth and development.
b)
Answer : Oxygen :
Oxygen present 21% percent in the air , Oxygen called active air because it supports life on earth and also support in burning or combustion .
c)
Answer : Carbon dioxide :
Carbon dioxide is very important for all living beings plants and animals , without carbon dioxide plants would not get enough energy to survive because photosynthesis process need carbon dioxide gas to produce energy . In humans also need carbon dioxide for regulations of blood pH , and respiratory drive .
d)
Answer : Water Vapour :
Water vapour is the most important greenhouse gas which is help in the process of water cycle , It is control earth temperature , rat of evaporation of living beings , and also determined climate condition of earth .
3)
a)
Answer : Pollutants :
The elements , substance or contaminants that pollute the natural environment and cause harmful or undesirable effects to the living beings in a visible way known as Pollutants .
b)
Answer : Acid rain :
Natural rain water are chemically combine with acidic pollutants like sulphur dioxide , nitrogen oxides etc. to form acid in air which mix with nature water , it get acidic this acidic rain water known as acid rain .
c)
Answer : Global warming :
The phenomenon of rising the average temperature of earth surface due increase the level of carbon dioxide, chlorofluorocarbon., methane, and nitrous oxide etc absorbed sun light and solar radiation , known as global warming.
d)
Answer : Smog :
A pollutants nitrogen oxides, sulphur oxides etc form a mixture of smoke and fog , this mixture known as smog.
4)
Answer : “Air is a mixture”, following evidences support this statement .
- Air has different properties at different times and palaces.
- Air contain different types of gases which retain their properties .
- Constituent of air can be separate by physical separation method.
5)
Answer : Air Pollution :
Contamination and harmful undesirable substance present in the air and get air polluted known as air pollution .
Harmful effects of sulphur dioxide, Nitrogen dioxide , and hydrogen sulphide present in the air are following .
- Sulphur dioxide and Nitrogen dioxide can effect on lungs ,and cause serious respiratory infection , asthma , chronic lungs disease.
- Sulphur dioxide can destroyed ozone layer .
- Nitrogen dioxide form a smog which harmful for eyes.
- Due to hydrogen sulphide harmful effects occur in living beings likeheadache , vomiting , coughing , and breathing problems.
- Sulphur dioxide, nitrogen dioxide, hydrogen sulphide cause acid rain .
6)
a)
Answer : Causes of air pollutions are following .
- Sulphur dioxide , nitrogen dioxide , hydrogen sulphide are produced from burning of fossil fuel .
- Agriculture chemicals produced harmful constituent in the atmosphere and make air polluted.
- Industries , factories , power plants produce high amount of toxic gases , and harmful chemicals in the atmosphere.
- House hold cleaning products , painting materials emits toxic fumes in the indoor air .
b)
Answer : Prevention of air pollutions are following .
- Planting more trees around us .
- Preparing manure from dried leaves and other biodegradable wastes rather than burning them .
- Reducing vehicle exhaust .
- Using less pollution fuel.
- Avoid usage of crackers .
- Avoid using chemicals products.
- Reduced the use of fire and fire products.
Exercise -II Solution:
1)
a)
Answer : Oxygen .
b)
Answer : Hydrogen peroxide ( H₂O₂)
c)
Answer : Tin.
e)
Answer : Air and Water .
f)
Answer : Mercuric oxide and potassium chlorate
g)
Answer : Sodium and carbon
2)
a)
Answer : Oxygen is prepared in the laboratory by downward displacement process are following .
- Take a small quantity of Manganese dioxide powder in round bottom flask .
- In the Round bottom flask mouth fitted with small funnel and glass tube , this glass tube attached with flat beaker containing water .
- In This water containing flat beaker placed inverted gas jar .
- When hydrogen peroxide add to round bottom flask drop by drop through funnel .
- Round bottom flask contain Manganese dioxide decomposed hydrogen peroxide and produce oxygen which go to flat water break from glass tube attached with mouth of round bottom flask.
- From the water beaker oxygen goes upward and stored in inverted gas jar , in this way oxygen is get through downward displacement process from water beaker.
b)
Answer : Manganese dioxide act as a catalyst in the preparation of oxygen .
c)
Answer :
d)
Answer : Hydrogen peroxide is preferred in the preparation of oxygen because it’s not a harmful chemicals , or highly explosives chemical , it is a safe chemical , without heating we can prepare oxygen .
e)
Answer : Oxygen is collected by downward displacement of water because oxygen gas is slightly soluble in water and also less dense than water and heavier than air so it can collect by the process of downward displacement of water.
f)
Answer : When a glowing splinter is introduced in a jar containing oxygen , The glowing splinter conflagrate but does not catch fire.
g)
Answer : When oxygen gas is passed through Alkaline pyrogallol Solution , than Alkaline pyrogallol Solution turns brown colour.
3)
a)
Answer : (i) When mercuric oxide is heated it will break down or decomposed to give mercury and oxygen .
(ii) When Potassium Nitrate is heated decomposition reaction occur and it give potassium Nitride and oxygen
b)
Answer : Potassium chlorate is not used for the laboratory preparation of oxygen because potassium chlorate need strong heating , so it may cause crack or break of apparatus which is used in the preparation of oxygen.
4)
Answer : A binary chemical compounds of oxygen in which oxygen is chemically combine with another elements or substance known as oxide .
Example : Metallic oxide :
- Na₂O (Sodium oxide)
- CaO (Calcium oxide)
Non Metallic oxide :
- SO₂ (Sulphur dioxide)
- CO₂ (Carbon dioxide)
5)
Answer : Following are the three types of oxidation process in which large amount of heat and light produced .
1) Slow oxidation .
2) Fast oxidation .
3) Spontaneous oxidation.
6)
a)
Answer : Sulphur :
When sulphur is heated and testwith litmus paper , then moist blue litmus paper turn into red
b)
Answer : Phosphorus :
When Phosphorus is heated and test with litmus paper , then moist blue litmus paper turn into red
c)
Answer : Calcium :
When Calcium is heated and test with litmus paper , then moist red litmus paper turn into blue.
d)
Answer : Magnesium :
When sulphur is heated and test with litmus paper , then moist red litmus paper turn into blue.
8)
a) .
Answer : Following are uses of oxygen .
- Oxygen is used all living organisms for breathing .
- Oxygen is used in some medicine to treat respiratory problems.
- Oxygen (O3) is a part of ozone layer which protects us ultraviolet rays from sunlight.
- Oxygen is used many of steal industries.
- Oxygen is used for the burning of fuel .
b)
Answer : All living organisms need oxygen for breathing , oxygen level balance in the atmosphere due to the green plants, because green plants give oxygen to the atmosphere by the process of photosynthesis. When Carbon dioxide and water chemically react with each other in presence of sunlight than green plants produced glucose for themselves and oxygen gas released , in this way oxygen naturally renewed in the air.
9)
Answer :
Sr.No | Rusting | Burning |
1) | Rusting is process when iron or metal slowly react with oxygen to produce radish brown substance on metal called rust . | Burning is the fast Oxidation process in which large amount of heat and light produced. |
2) | It need air and moisture | It only need air |
3) | Rusting mainly occur on the surface of iron and it’s Alloys. | Burning can occur whole body of substance that is wood , paper , metal , plastic etc. |
4) | Heat is not required for rusting. | Heat is required for burning. |
OBJECTIVE TYPE QUESTIONS
1)
a) …………. Is the most abundant inert gas present in air.
Answer : Argon
Explanation: Argon gas is the most abundant Inert gas present in air of the stable nucleus and inert properties.
b) Oxide of sulphur and nitrogen combine with rain water to form …….…..and ……….. which cause ……….
Answer : Sulphuric acid , Nitric Acid , Acid rain
Explanation: When oxide of sulphur and nitrogen combine with rain in air to form Sulphuric acid and nitric acid which cause acid rain.
c) …………..and………..are most common air pollutions.
Answer : NO₂ and CO
Explanation: Nitrogen dioxide and carbon monoxide are the most common air pollutions because it produced in large amount through road vehicle burning fuel .
d) …………. Discovered the oxygen gas.
Answer : Joseph priestly
Explanation: Joseph Priestley discovered oxygen gas in 1774.
e) Oxygen occupies about………..of air volume.
Answer : 21%
Explanation: Oxygen gas occupies 21% in the air from total gas.
2)
Answer :
Column A | Column B |
a) Global warming |
iv) Methane |
b) Acid rain | v) Nitrogen dioxide |
c) Rust | i) Hydrated Ferric oxide |
d) Catalyst | ii) Manganese dioxide |
e) Photosynthesis | iii) Carbon dioxide |
MULTIPLE CHOICE QUESTIONS
1)
Answer : d) CNG
Explanation: Compressed natural gas (CNG) burn with less pollution as compared to other fuel that is why CNG also called clean gas or clean fuel.
2)
Answer : a) Photosynthesis
Explanation: When Carbon dioxide and water chemically react with each other in presence of sunlight than green plants produced glucose for themselves and oxygen gas released in the air , So photosynthesis is the natural way to adding oxygen to air in which green plants.
3)
Answer : c) an iron hammer
Explanation: Iron is most reactive transition elements which chemical react with oxygen and moisture present in the atmosphere and form radish brown counting of rust on its surface.