Kerala Syllabus Class 9 Chemistry Chapter 7 Non Metals Notes Solutions

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Kerala SCERT Class 9 Chemistry Chapter 7 Solutions Non Metals

Kerala Syllabus Std 9 Chemistry Chapter 7 Non Metals Notes Solutions Questions and Answers

Class 9 Chemistry Chapter 7 Let Us Assess Answers Non Metals

Question 1.
Some gases are given in the following box. Choose suitable answers from the box and answer
the questions below.
Hydrogen, Chlorine, Oxygen, Nitrogen
a. Which gas is formed in the thermal decomposition of KMn04?
b. Which gas is used for the purification of water?
c. Which element is essential for the growth of plants?
d. Which is the inflammable gas obtained during the electrolysis of water?
Answer:
a. Oxygen.
b. Chlorine.
c. Nitrogen.
d. Hydrogen.

Question 2.
Find examples of allotropes of carbon and complete the table.

Crystalline allotropes	Amorphous allotropes

Answer:

Crystalline allotropes	Amorphous allotropes
Diamond, Graphite, Fullerenes, Graphene	Charcoal, Carbon Black, Soot, Lampblack

Question 3.
An experiment is given to identify chloride salt. Write down the observations and inferences.

Experiment	Observation	Inference
i. Add AgNO3 solution to the given salt solution.
ii. Add NH4OH solution to the precipitate formed

Answer:

Experiment	Observation	Inference
i. Add AgNO3 solution to the given salt solution.	A white precipitate forms.	The formation of this white precipitate indicates the presence of Cl– ions in the original salt solution.
ii. Add NH4OH solution to the precipitate formed	The white precipitate of AgCl dissolves in the NH4 OH solution, forming a colouriess solution.	This solubility of AgCl in NH4OH is a characteristic property of AgCl. It confirms the presence of Cl– ions in the original salt solution.

Question 4.
Find the suitable gas for each of the following situations. (Chlorine, nitrogen, CFC, oxygen)
• As an oxidising agent in rocket fuels.
• Depletion of ozone.
• To inflate the tyres of vehicles.
Answer:
As an oxidising agent in rocket fuels – Oxygen
Depletion of ozone – CFC, Chlorine
To inflate the tyres of vehicles – Nitrogen

Question 5.
Potassium permanganate is heated in a boiling tube.
a. A burning matchstick is inserted into the mouth of the boiling tube. Write down your observation.
b. Which gas is produced?
Answer:
a. Observation: When a burning matchstick is inserted into the mouth of the boiling tube containing heated potassium permanganate, the matchstick will reignite with a bright flame.

b. The gas produced during the decomposition of potassium permanganate is oxygen. The oxygen gas supports combustion, hence the reignite of the matchstick.

Question 6.
Write the answers to the following questions on the preparation of chlorine gas in the laboratory.
a. What are the chemicals required to prepare chlorine gas?
b. Chlorine gas is collected by passing it through water. Why?
c. Chlorine gas is passed through concentrated sulphuric acid. Why?
Answer:
a. Potassium permanganate (KMnO₄)

Concentrated hydrochloric acid (HCl)

b. To remove the HCl vapours.

c. Chlorine gas is passed through concentrated sulphuric acid to remove any water vapour that may have been carried over from the reaction mixture. Concentrated sulphuric acid is a dehydrating agent, which means it can absorb water from other substances.

Question 7.
The bleaching action of chlorine requires moisture. Give reason
Answer:
Chlorine gas reacts with water to form hypochlorous acid.

• Hypochlorous acid is the active bleaching agent.
• The reaction between chlorine gas and water requires moisture.
• Without moisture, chlorine gas will not have any bleaching action.

Question 8.
“Chemical fertilisers must be banned completely, and organic fertilisers must be promoted.” What is your opinion about this argument? Justify your answer.
Answer:
Reasons to Ban:

• Environmental Health: Chemical fertilisers can harm soil and water, so reducing them can help ecosystems.
• Sustainability: Organic fertilisers are often better for long-term soil health
• Human Health: Less chemical use means fewer harmful residues in food and water.

Reasons Against Ban:

• Food Production: Chemical fertilisers help increase crop yields, which is vital for feeding a growing population.
• Farmer Struggles: Farmers who rely on chemicals may have a hard time switching to organic
  methods without support.

Question 9.
a. What are the chemicals required for preparing hydrogen in the laboratory? b. How will you identify that the gas obtained is hydrogen?
Answer:
a. Zinc granules: A reactive metal that reacts with acids to produce hydrogen.
Dilute hydrochloric acid: The acid reacts with the zinc to produce hydrogen gas
Zn + 2HCl → ZnCl₂ + H₂

b. Hydrogen gas can be identified by a simple test known as the “pop” test.
Collect the gas produced in a test tube.
Bring a lighted splint near the mouth of the test tube.
Observe the reaction: If the gas is hydrogen, it will ignite with a “pop” sound

Question 10.
a. What are the merits of hydrogen when it is used as a fuel?
b. What are the isotopes of hydrogen?
c. Which among these is an isotope without a neutron?
Answer:
a. High calorific value.
Clean combustion.
Abundant availability.
Possibility of pollution is low.

b. Hydrogen has three isotopes:
Protium: The most common isotope, with one proton and no neutrons in its nucleus.
Deuterium: An, isotope with one proton and one neutron in its nucleus.
Tritium: An isotope with one proton and two neutrons in its nucleus.

c. Protium

Question 11.
a. What is meant by calorific value?
b. Some fuel is given in the box. Which has the highest calorific value?
Petrol, Coal, Ethanol, Hydrogen, Methanol
c. Hydrogen is not used as a domestic fuel. What are the reasons for this limitation?
Answer:
a. The calorific value of a fuel is the heat energy released from unit mass of the fuel on complete combustion.

b. Hydrogen.

c. Hydrogen is a gas that bums with an explosion.
It is difficult to store and distribute hydrogen.
Safety concerns.
High Cost.
Technological limitations.

Question 12.
One of the crystalline forms of carbon is diamond. Diamond does not conduct electricjty. Why?
Answer:
In diamond, each carbon atom is covalently bonded to four other carbon atoms surrounding it. This
strong bond is responsible for the hardness of the diamond. Due to the absence of free electrons in this crystalline structure, diamond does not conduct electricity.

Question 13.
a. Which allotrope of carbon is a conductor of electricity?
b. Give a reason for this.
c. Write down any two uses of this allotrope.
Answer:
a. Graphite

b. The reason for graphite’s electrical conductivity lies in its unique structure:
Layered Structure: Graphite has a layered structure, where each layer consists of carbon atoms arranged in hexagonal rings.

Free Electrons: Within each layer, one of the carbon atom’s valence electrons is delocalised and can move freely between the hexagonal rings. These delocalised electrons act as charge carriers, allowing graphite to conduct electricity.

c) Graphite is used as the “lead” in pencils.
Graphite is used as an electrode in various types of batteries, such as lithium-ion batteries.

Question 14.
Match the following

A	B
Diamond	Nanotechnology
Graphite	Making of ornaments
Graphene	Lubricants

Answer:

A	B
Diamond	Making of ornaments
Graphite	Lubricants
Graphene	Nanotechnology

Question 15.
a. Dilute hydrochloric acid and calcium carbonate are taken in a test tube. Which gas is produced? b. Complete the chemical equation of the reaction.
CaCO₃ + 2HCl → CaCl₂ + …………… + ……………
c. The gas obtained is passed through clear lime water. Write down the observation.
Answer:
a. Carbon dioxide (CO₂) gas is produced.

b. CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

c. When the gas obtained r(carbon dioxide) is passed through clear lime water (calcium hydroxide solution), it turns the lime water milky.

Extended Activities

Question 1.
Write a short note on the bleaching property of chlorine and present it.
Answer:
Chlorine is a powerful oxidising agent, which means it can remove electrons from other substanCes. This property allows chlorine to act as a bleaching agent, breaking down coloured compounds and making them colourless.
When chlorine comes into contact with a coloured compound, it oxidises the coloured molecules, breaking down their chemical structure.
The oxidation process results in the loss of colour, as the coloured molecules are transformed into colourless products.

Applications of Chlorine Bleaching:
Textile Industry: Chlorine is used to bleach cotton, linen, and other fabrics.
Paper Industry: Chlorine is used in the pulp and paper industry to bleach wood.
Water Treatment: Chlorine is added to drinking water and swimming pools to disinfect and remove impurities.

Question 2.
Prepare a table showing the use of oxygen, nitrogen and hydrogen in daily life.
Answer:

Gas	Common use
Oxygen	Breathing, medical treatments, industrial processes (combustion, steelmaking), rocket fuel, oxyacetylene flames is used for welding.
Nitrogen	Fertilizer production, food packaging (to prevent spoilage), industrial gases (creating inert atmospheres), automotive airbags, In the production of ammonia.
Hydrogen	Fuel cells (generating electricity), rocket fuel, production of ammonia (fertilizers), hydrogenation of fats and oils, used as an reducing agent in metal production.

Question 3.
Visit any chemical fertiliser factory, prepare a project report and present it
Answer:
Guidelines for Preparing Your Chemical Fertiliser Factory Project Report
1. Introduction:

• Clearly state the purpose of your visit and the overall goal of the report.
• Provide a brief overview of the factory, including its name, location, and any relevant background information.

2. Factory Tour:

• Describe the physical layout and facilities of the factory.
• Discuss the production process, step-by-step, including any diagrams or flowcharts to illustrate the process

3. Raw Materials and Production:

• Identify the primary raw materials used in fertiliser production.
• Explain the chemical reactions involved in the manufacturing process.
• Discuss any specific equipment or machinery used.

4. Environmental Impact:

• Assess the potential environmental impacts of fertiliser production (Eg: water pollution, airpollution, soil contamination).
• Discuss any sustainability initiatives or measures taken by the factory to minimise
  environmental harm.

5. Safety Measures:

• Describe the safety precautions and regulations implemented at the factory.
• Discuss any potential hazards or risks associated with fertiliser production.

6. Technology and Innovation:

• Highlight any advanced technologies or innovative practices used by the factory.
• Discuss the potential benefits of these technologies.

7. Challenges and Future Outlook:

• Identify any challenges or obstacles faced by the factory.
• Discuss the factory’s future plans and goals.

8. Conclusion:

• Summarize the key findings and observations from your visit.
• Offer your personal reflections or insights.
• Provide any recommendations or suggestions for improvement.

Non Metals Class 9 Notes Questions and Answers Kerala Syllabus

Question 1.
Examine the periodic table, find out some examples of metals, non metals and metalloids, and

Metals	Non metals	Metalloids

Answer:

Metals	Non metals	Metalloids
Sodium Potassium Magnesium Calcium Aluminium Iron Copper Gold	Carbon Nitrogen Oxygen Hydrogen Chlorine Sulphur Fluorine	Metalloids Boron Silicon Germanium Arsenic Antimony Tellurium

Hydrogen, carbon, oxygen, nitrogen and chlorine are some important non-metals. Let us examine the methods of their preparation and some of their physical and chemical properties.

Hydrogen is the most abundant element in the universe. It is the major component of the sun and other stars. Hydrogen is seen in the atmosphere in a very small quantity in free state.

Question 2.
Complete the given table and write a short note on hydrogen.
Answer:

Atomic Number	1
Mass number	1
No. of electrons	1
No. of protons	1
No. of neutrons	No neutrons
Solubility in water	Insoluble in water
Isotopes	Protium, Deuterium, Tritium

Question 3.
Take 5 mL of dilute hydrochloric acid in a test tube. Add some zinc granules to it. Record your observation.
a) Is the gas produced hydrogen? How do you confirm it? Insert a burning splint to the mouth of the test tube. What do you observe?
Answer:
Yes, the hydrogen gas bums with a pop sound. Hydrogen is a flammable gas.

b) Write the balanced chemical equation of the above reaction.
Answer:
Zn + 2HCl → ZnCl₂ + H₂
Hydrogen is industrially prepared by the electrolysis of water.

Question 4.
To which category do the above reactions belong?
(Combination reaction, displacement reaction, decomposition reaction)
Answer:
Combination reaction.

Question 5.
The graph given below shows some fuels and their calorific values.

a. Which fuel has the lowest calorific value?
Answer:
Carbon monoxide.

b. Which fuel has the highest calorific value?
Answer:
Hydrogen.

c. What is the product obtained when hydrogen burns in air?
Answer:
Water.
The calorific value of hydrogen is higher than that of other fuels.

The merits of hydrogen as a fuel:

• When hydrogen is used as a fuel, the possibility of pollution is very low since water is the only product formed.
• High calorific value

In spite of these merits, hydrogen is not used as a domestic fuel due to the below-given limitations:

• Hydrogen is a gas that bums with an explosion.
• It is difficult to store and distribute hydrogen.

If these limitations are overcome, hydrogen will become a universal fuel. The problems like the scarcity of fossil fuels and environmental pollution can thus be resolved.

Question 6.
Which compounds of hydrogen are known to you?
Answer:
Water, Acids, Alkalies, Carbohydrates, Oils, Sugar

Question 7.
Which properties of hydrogen are used in the following situations?
a. Balloons filled with hydrogen fly high in the air.
b. Used as fuel.
Answer:
a. Hydrogen has less density than air

b.

• High calorific value
• The possibility of pollution is very low.
• Ease in preparing.

Question 8.
Prepare a note on the possibility of using hydrogen as a fuel.
Answer:
Hydrogen as a fuel:
Hydrogen is a colourless, odourless, tasteless gas that is highly flammable. It is the most abundant element in the universe and is found in water, natural gas, and other sources. Hydrogen can be used as a fuel in a variety of ways, including in fuel cells, internal combustion engines, and gas turbines.

Advantages of Hydrogen as a Fuel

• Hydrogen is a clean fuel that produces no greenhouse gases when burned.
• Hydrogen has a high energy density, which means that it can be stored in a small space and used to generate a large amount of energy.
• Hydrogen can be used in a variety of engines and fuel cells, making it a versatile fuel option.
• Hydrogen can be produced from a variety of sources, including renewable energy sources such as wind, solar, and geothermal power.

Disadvantages of Hydrogen as a Fuel:

• Hydrogen is a flammable gas, which means that it must be stored and handled carefully.
• Hydrogen is currently more expensive to produce than other fuels, such as gasoline and diesel.
• Hydrogen infrastructure is not yet widely available, which can make it difficult to refuel hydrogen-powered vehicles.

Future of Hydrogen as a Fuel:
Despite the challenges, hydrogen has the potential to become a major source of energy in the future. As technology advances and the cost of producing hydrogen decreases, it is likely that hydrogen will become a more viable option for transportation and other applications.

• Almost all substances around us contain carbon.
• Carbon is found both in an elemental state and a combined state in nature.

Question 9.
Examine the periodic table and record the position, atomic number and electronic configuration of carbon in your science diary.
Answer:
Atomic number – 6
Electronic configuration – 2, 4
Period – 2
Group – 14

Question 10.
In diamond, each carbon atom is covalently bonded to how many surrounding carbon atoms?
Answer:
In diamond, each carbon atom is covalently bonded to four surrounding carbon atoms.

Question 11.
What is the valency of carbon?
Answer:
The valency of carbon is 4.

Question 12.
Are free electrons present in the diamond?
Answer:
No, free electrons are not present in diamonds.

Properties of diamond

• Hardness is very high.
• Do not conduct electricity.
• High thermal conductivity.
• High refractive index.

Question 13.
Find out the reason for using diamonds for making ornaments and cutting glasses.
Answer:
Diamonds are used for making ornaments and cutting glasses due to their unique properties:

• Hardness
• Durability
• Precision

Question 14.
Some uses of graphite are given below. Find out and write the characteristics and properties that facilitate it.
a) Used as an electrode in dry cell
b) Used to make pencil lead
c) Used as a lubricant
Answer:
a) Used as an electrode in dry cell
Property: Good electrical conductivity
Characteristic: Graphite’s layered structure allows for the easy movement of electrons, making it an excellent conductor of electricity. This property is essential for its use as an electrode in dry cells, where it facilitates the flow of electrical current.

b) Used to make pencil lead
Property: Soft and easily markable
Characteristic: Graphite’s layered structure allows the layers to slide over each other easily, making it soft and easily markable. This property is ideal for pencil lead, as it allows the graphite to leave a mark on paper with minimal pressure.

c) Used as a lubricant
Property: Low friction between layers.
Characteristic: The force of attraction between these layers is weak. Hence, one layer can slide over the other. So, graphite is used as a lubricant

Question 15.
List out and compare the properties of graphite and diamond
Answer:

Graphite	Diamond
Layered structure with hexagonal rings of carbon atoms	Three-dimensional network structure with tetrahedral arrangement of carbon atoms
Soft	Extremely hard
Good conductor	Insulator
High thermal conductivity	High thermal conductivity
Lubricant, pencils, electrodes	Cutting tools, jewellery, abrasives

Question 16.
What are the carbon compounds that you know?
Answer:
Carbon dioxide (CO₂)
Carbon monoxide (CO)
Carbonates (CO₃^2-)
Bicarbonates

Question 17.
Which of these compounds contain carbon and oxygen?
Answer:
Carbon dioxide (CO₂)
Carbon monoxide (CO₂)
Carbonates (CO₃^2-)
Bicarbonates

Question 18.
What is the major compound produced when carbon or carbon compounds burn in the air?
Answer:
Carbon dioxide (CO₂).
C + O₂ → CO₂
Preparation of carbon dioxide in the laboratory

Question 19.
What are the reactants used here?
Answer:
Calcium carbonate, Diluted HCl

Question 20.
Complete the chemical equation of the reaction.
Answer:
CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

Question 21.
How can we identify that the gas formed here is CO₂?
Answer:
When the gas formed is passed through lime water (Ca(OH)₂), if it turns milky we can say that the gas is Carbon dioxide (CO₂).

Carbon dioxide gas is produced when calcium carbonate and dilute hydrochloric acid react with each other. When this gas is passed through lime water Ca(OH)2, it turns milky.

Uses of Carbon dioxide

• In fire extinguishers.
• To make soda water and soft drinks.
• In the manufacture of washing soda (Na₂CO₃.10H₂O), and baking soda (NaHCO₃).
• In the manufacture of chemical fertilisers like urea.
• In Carbogen (95% oxygen and 5% carbon dioxide), which is used for artificial respiration.
• Solid carbon dioxide is known as dry ice. It is used to create a smoky effect in stage shows etc.

Question 22.
Tick the properties of carbon dioxide from the following.
Answer:

• Coloured / colourless (√)
• Helps combustion / does not help combustion (√)
• Odourous / odourless (√)
• Denser than air (√) / lighter than air
• Aqueous solution – Acidic (√) / Basic

Question 23.
Match the columns A and B suitably.

A	B
Washing soda	NaHCO3
Carbon monoxide + Hydrogen	Na2CO3.10H2O
Baking soda	Producer gas
	Water gas

Answer:

A	B
Washing soda	Na2CO3.10H2O
Carbon monoxide + Hydrogen	Water gas
Baking soda	NaHCO3

 

• Nitrogen is the most abundant gas in the atmosphere.
• Nitrogen is present in all living beings.
• Nitrogen is an element that is essential for the growth of plants.

Question 24.
Under normal circumstances, atmospheric nitrogen is inert. Write down the reason.
Answer:
Inert behaviour refers to the tendency of a substance to resist chemical reactions. An inert substance is relatively unreactive and does not readily combine with other elements or compounds.

Reason:

• Triple Covalent Bond: Nitrogen atoms share three pairs of electrons, forming a very stable bond. This bond is much stronger than a single or double bond.
• High, Activation Energy: Breaking this triple bond requires a high activation energy, which is the minimum amount of energy needed to start a chemical reaction. This high energy barrier makes it difficult for nitrogen to react with other substances.

Question 25.
Which gas helps combustion?
Answer:
Oxygen.

Question 26.
Which gas helps to control the rate of combustion?
Answer:
Nitrogen.
Plants cannot absorb nitrogen directly from the atmosphere. It involves following steps

Step: 1
Through thunder and lightning: The triple bond in the nitrogen molecule is broken down during thunder and lightning, and nitrogen combines with atmospheric oxygen to form nitric oxide (NO). N₂ + O₂ → 2NO
The nitric oxide thus produced combines with more oxygen to form nitrogen dioxide (NO₂).
2NO + O₂ → 2NO₂
In the presence of oxygen, nitrogen dioxide dissolves in rainwater and reaches the soil as nitric acid (HNO₃).
4NO₂ + 2H₂O + O₂ → 4HNO₃
This nitric acid reacts with the minerals in the soil and forms nitrate salts which are absorbed by plants.

Step: 2
Through nitrogen fixation: Rhizobium bacteria in the roots of leguminous plants absorb atmospheric nitrogen and convert it into compounds that can be absorbed by the plants.

Question 27.
What are the methods by which we can supply the elements required for plant growth in large amounts?
Answer:
Use of organic fertilisers
Use of chemical fertilisers
Merits and demerits of chemical and organic fertilisers

Organic fertilisers	Chemical fertilisers
Eco friendly	Increase crop yield
Maintain the original nature of the soil	Easily available
Delay in making the nutrients available	Quick supply of the three nutrients (N, P, K)
Do not destroy microorganisms in the soil	Change the organic structure of the soil.
More quantity is required.	Increase the acidity of the soil.
Reduce the possibility of pollution.	Cause pollution.

Question 28.
Observe the picture of the preparation of oxygen in the laboratory.
a. Which is the reactant in this chemical reaction?
Answer:
Potassium permanganate

b. Heat the boiling tube containing potassium permanganate.
Insert a burning matchstick to the mouth of the boiling tube. What is the observation?
Answer:
The glowing matchstick flares up.

c. Complete the chemical equation of the reaction.
Answer:

d. Pick out from the following the physical properties suitable to oxygen. Write them down.
Answer:

Colour	Yes/ No √
Odour	Yes/ No √
Solubility in water	Soluble √ / Insoluble
Nature of combustion	Bums/ Helps to burn

Oxygen is manufactured by the electrolysis of water.

Question 29.
Haven’t you noticed that some metals lose lustre in the course of time due to their reaction with oxygen? Write the reason.
Answer:
Oxygen reacts with metals and non-metals to produce their oxides. Due to this, metals lose lustre in the course of time.

Question 30.
Prepare a note on the role of plants in maintaining the level of oxygen in the atmosphere. Present it in the class.
Answer:
Plants play a crucial role in maintaining the oxygen levels in our atmosphere. Through the process of photosynthesis, plants convert carbon dioxide into oxygen, a gas essential for the survival of most life on Earth.

Photosynthesis is a complex process that occurs in the chloroplasts of plant cells. It involves the use of sunlight, water, and carbon dioxide to produce glucose and oxygen. The chemical equation for photosynthesis is:
6CO₂ + 6H₂O + sunlight → C₆H₁₂O₆ + 6O₂

The oxygen produced by plants is released into the atmosphere, where it is used by animals, humans, and other organisms for respiration. During respiration, these organisms consume oxygen and release carbon dioxide back into the atmosphere. This creates a continuous cycle of oxygen and carbon dioxide exchange.

Question 31.
Conduct a seminar on ozone depletion and its solutions.
Answer:
Seminar: Ozone Depletion and Its Solutions

Introduction:
The ozone layer, a vital shield in Earth’s atmosphere, is facing a serious threat: depletion. This depletion has far-reaching consequences for human health, ecosystems, and the planet as a whole. In this seminar, we will explore the causes, effects, and potential solutions to ozone depletion.

Causes of Ozone Depletion:
Chlorofluorocarbons (CFCs): These man-made chemicals, once widely used in refrigerants, aerosols, and foam insulation, are the primary culprits in ozone depletion. When released into the atmosphere, CFCs rise to the stratosphere and react with ozone molecules, destroying them.

Effects of Ozone Depletion:
Increased UV Radiation: Ozone depletion allows more harmful ultraviolet (UV) radiation to reach Earth’s surface.
This can lead to:

• Skin cancer
• Cataracts
• Weakened immune systems
• Damage to plants and marine ecosystems

Climate Change: Ozone depletion can indirectly contribute to climate change by affecting atmospheric circulation and temperature patterns.

Solutions to Ozone Depletion:

• Raising awareness about the importance of the ozone layer and the consequences of its depletion.
• Encouraging people to choose products that are ozone-friendly.
• Strict regulations and enforcement are essential.
• Develop advanced monitoring techniques to track ozone levels.

Question 32.
Complete the table about chlorine after analysing the periodic table.
Answer:

Atomic number	17
Electronic configuration	2, 8, 7
Mass number/Atomic mass	35
No. of electrons	17
No. of neutrons	18
Valency	1
Name of the element family	Halogen

Question 33.
Analyse the given figure depicting chlorine preparation and write answers to the questions given below.

a. What are the chemicals required to prepare chlorine in the laboratory?
Answer:
Potassium permanganate (KMnO₄), Concentrated Hydrochloric acid (Con. HCl)

b. What are the products formed?
Answer:
Potassium chloride (KCl), Manganese chloride (MnCl₂), Water (H₂O), Chlorine gas (Cl₂).

Question 34.
The chlorine gas obtained is collected in the jar after passing it first through water and then through sulphuric acid. Why is it done so?
Answer:
A small amount of hydrogen chloride vapour is also released along with the chlorine gas. Hydrogen chloride vapours dissolve in water when passed through it. Sulphuric acid can absorb the water vapour in the chlorine gas. So it is passed through concentrated sulphuric acid.

PROPERTIES OF CHLORINE

• Greenish yellow in colour
• Pungent smelling.
• Denser than air.

Question 35.
Take two jars filled with chlorine gas. Take a coloured cloth and cut it into two pieces. Put a wet piece into one jar and the other dry piece of cloth into the second jar. What happens to the colour of the cloth in the two jars?
Answer:
The cloth in the first jar remains unchanged in colour. The colour of the wet cloth in the second jar disappears. This is because of the bleaching properties of chlorine. Chlorine bleaches coloured materials into colourless materials in the presence of moisture.
H₂O + Cl₂ → HCl + HOCl
HOCl → HCl + [O]
Water reacts with chlorine to form hydrochloric acid and hypochlorous acid. Hypochlorous acid is unstable. So, it decomposes to form hydrochloric acid and nascent oxygen. Nascent oxygen acts as a powerful oxidising agent to decolourise the coloured substances.

Question 36.
Some questions are given below. Find suitable answers from the box given. Write them down.
Nitrogen, Nitric oxide, Oxygen, Carbon, Carbon dioxide
a) Which gas is obtained when potassium permanganate is heated?
b) What is the product formed when nitrogen combines with oxygen at high temperatures?
c) Which reactant is used along with hydrogen for the manufacture of ammonia?
Answer:
a) Oxygen
b) Nitric oxide
c) Nitrogen