Maharashtra Board Class 9 Science Chapter 13 Carbon An important element Solution

Maharashtra Board Class 9 Science Solution Chapter 13 – Carbon An important element

Balbharati Maharashtra Board Class 9 Science Solution Chapter 13: Carbon An important element. Marathi or English Medium Students of Class 9 get here Carbon An important element full Exercise Solution.

Std	Maharashtra Class 9
Subject	Science Solution
Chapter	Carbon An important element

1.) Select the proper options and complete the statement.

(Single, all, double, ionic, carbon, give and take, hydrogen, multiple, share, most, covalent)

Ans:

a) A carbon atom forms a covalent bond with other atoms. In this bond the two atoms share

b) All the bonds in a saturated hydrocarbon share

c) At least one carbon bond in an unsaturated hydrocarbon is double.

d) Carbon is the essential element in all the organic compounds.

e) The element hydrogen is present in all organic compounds.

2.) Answer the following questions.

a) Why are carbon and it’s compounds are used as fuel?

Ans:

As carbon and it’s compounds after combustion produces large amount of heat and also energy. So to gain more heat and energy carbon and it’s compounds are mainly used as fuel.

b) In which compounds forms does carbon occurs?

Ans:

• Carbon exist in various forms in its compounds. Some of the carbon compounds are as follows.
• In hydrocarbons mainly hydrogen and carbon are the important element.
• Carbon also exist in the form of methane.
• The carbon dioxide gas which exist in free state also contains carbon.
• When fossil fuels and wood are burnt then carbon dioxide gas releases in environment.
• There are lot of compounds exist in nature which are made from carbon.

c) Write the uses of diamond?

Ans:

The following are the uses of diamond.

• We know that diamond is the allotropes of carbon which is the hardest in nature.
• Diamond is mostly used in ornaments which are most expensive.
• As diamond is hardest it is used in cutting glasses and also used in rock drilling machines.
• By using diamond dust other diamond are also polished.
• In space and in artificial satellites window are made from diamond to protect from harmful radiation’s coming from the sun.
• In eye surgery diamond knives are also used.
• Due to the hardest property of diamond it is used in most of the cases.

3.) Explain the difference.

a) Diamond and graphite:

Diamond and graphite both are the allotropes of the carbon but having some difference which are discussed below.

Diamond:

• In diamond each carbon atom is fixed in the place which is surrounded by other four carbon atoms and each side of diamond forms double pyramids.
• Diamond is the hardest and colourless allotropes of carbon existing in nature.
• The refractive index of diamond is high and near about 2.5
• Although diamond is hardest in nature but it is bad conductor of electricity.
• As there are no free electrons are easily available in diamond hence it is chemically inert under normal conditions.

Graphite:

• In graphite carbon atoms are situated in flat planes of hexagonal rings in a such way that they forms the stack.
• Graphite is soft in nature, greyish in colour and slippery when we touch to it.
• Graphite is an opaque substance.
• Graphite is good conductor of heat and also electricity.
• Graphite is slightly reactive than diamond as some free electrons are available for chemical reaction.

b) Crystalline and non crystalline forms of carbon

Ans:

Crystalline forms of carbon:

• These are having definite shape due to the periodic arrangement of its atoms.
• These are having long range order of its constituent particles.
• These solids are having sharp and high melting point.
• These are having definite heat of fusion.
• These solids are anisotropic in nature and these are the true solids.

Non crystalline forms of carbon:

• These are having irregular shape with short range order of its constituent particles.
• These solids may melt and soften over certain range of temperature.
• These solids are not having specific heat of fusion due to their irregular shape.
• These solids are isotropic in nature and they are pseudo solids or super cooled liquids.

 4.) Write scientific reasons.

a) Graphite is a conductor of electricity.

Ans:

In graphite some free electrons are available which are in between the layers.

As these free electrons are easily available for conduction and hence graphite acts as a good conductor of electricity.

b) Graphite is not used in ornaments.

Ans:

• We use those substances which are having lustre, which are easy to mould in making ornaments.
• Gold and silver are the substances having lustre, easy to mould in required shape so we use them for making jewellery.
• But, graphite is soft in nature, brittle and slippery. Also graphite does not have lustre so it can’t be used in making ornaments.

c) Limewater turns milky when CO2 is passed through it.

Ans:

• When CO₂ is passed through the limewater it turns milky because there is formation of calcium carbonate.
• The following chemical reaction shows the formation of calcium carbonate when carbon dioxide is passed through limewater.

Ca(OH)₂ + CO₂ -> CaCO3 + H2O

d) Bio gas is an eco-friendly fuel.

Ans:

• Biogas provides fuel which is due to the decomposition of organic waste.
• And it doesn’t enhance the greenhouse effect and helps in decaying the greenhouse gases.
• Also it is the best fuel as compared to other fuels because it is eco-friendly.

 5.) Explain the following.

1. a) Diamond, graphite and fullerenes are crystalline forms of carbon.

Ans:

• As we know that, carbon has the property of allotropy. That means it has three allotropes namely diamond, graphite and fullerenes.
• These are the crystalline solids which are having regular shape, sharp edges and plane surfaces.
• All these are the crystalline solids as they shows the property of crystalline solids.

b) Methane is called as marsh gas.

Ans:

Methane is used as the marsh gas because it is mostly occuring at the marshy places which are the lands surrounded by water for long period of time without trees.

c) Petrol, diesel, coal are fossil fuels.

Ans:

Petrol, diesel, coal are the fossil fuels as they are obtained from the dead plants and animals.

These fossil fuels are formed when the aquatic and terrestrial animals and plants get buried under the ground for many years. Hence these are the fossil fuels as they are formed from fossil

d) Uses of various allotropes of carbon.

Ans:

• There are various allotropes of carbon which are used in many ways.
• Diamond is used in cutting glasses and in drilling machines.
• It is used in ornaments also.
• In space and artificial satellites the windows are made from diamond to protect from the harmful radiation coming from sun.
• Diamond dust is also used in polishing the other diamond.

 

• Graphite is used mostly in making lubricant and in making carbon electrodes.
• It is also used in making pencils, in paints and also in polishes.
• Fullerenes are used as insulators and they are used as catalysts in water purification process.
• Coke and coal is used as fuel in factories and also in homes.
• All these are the uses of allotropes of carbon.

e) Use of CO₂ in the fire extinguisher.

Ans:

• Carbon dioxide is used in the fire extinguisher as it has cooling effect at high pressure.
• Also it removes the oxygen which is necessary for combustion process and thereby acts as the fire extinguisher.
• As it doesn’t conduct electricity hence it is used as ideal fire suppressant in electrical instruments like computers also.
• When it is used as fire extinguisher it doesn’t produces any harmful effects this is also the reason behind its use as fire extinguisher.

f) Practical uses of CO₂.

Ans:

• CO₂ is mainly used in making aerated drinks.
• Solid carbon dioxide is used to make milk and it’s products cool during the transportation.
• In dry cleaning liquid CO2 is used as solvent.
• CO₂ is also used as fire extinguisher under high pressure.
• Plants produces their own food by using carbon dioxide from air in the process of photosynthesis.

 6.) Write two physical properties of each.

a) Diamond:

• Diamond is the allotropes of carbon which is hardest in teh nature.
• It doesn’t conduct electricity and heat.
• It is colourless, transparent and brittle in pure form.

b) Charcoal:

• Charcoal is the brittle and highly porous material existing in nature.
• And it is also the bad conductor of electricity and heat.

c) Fullerenes:

• Fullerenes are the one of the allotropes of carbon which exist in the form of Bucky balls and Bucky tubes.
• Fullerenes are made from 60 C atoms.

 7.) Complete the following chemical reaction.

Ans:

a) CH4 + 2O2 -> CO2 + 2H2O + Heat

b) CH4 + Cl2 -> CH3Cl + HCl

c) 2NaOH + CO2 -> Na2CO3 + H2O

 8.) Write answers to he following in detail.

a) What are the different types of coal? What are their uses.

Ans:

• The different types of coal are peat, lignite, bituminous, anthracite etc.
• Lignite is used in the generation of electricity.
• Bituminous is used in all daily uses of coal.
• Anthracite is best suitable for the smelting of iron.

b) How will you prove experimentally that the graphite is a good conductor of electricity.

Ans:

• The following experiment should be performed to check whether graphite is good conductor or not.
• When we use two graphite ends of pencil in making circuit which contains bulb and cell also.
• When we complete the circuit and when both graphite ends of pencil are in the circuit, if at that time bulb glows then we say that graphite conducts electricity.
• Otherwise if bulb doesn’t glow then we can say that graphite does not conducts electricity.

c) Explain the properties of carbon.

Ans:

• Carbon is the soft, faint in greyish and it is the non metal.
• According to its existence that is crystalline or non crystalline it has property of allotropy.

Reaction with O₂:

• Carbon burns with oxygen to form CO2 and light, heat is evolved hence it is called as combustion reaction.

Oxidation of carbon:

• When pure carbon get oxidised it form CO2 showing combustion reaction.

Addition reaction:

• In the hydrocarbons contains carbon elements like hydrogen, chlorine and bromine are added across the double, triple bond exist in hydrocarbons.

Substitution reaction:

• In this reaction one of the atom or group of atom is replaced with the other atom.
• When methane reacts with Cl2 in the presence of sunlight, one of the hydrogen is replaced by the chlorine and methyl chloride with HCl us formed.

CH4 + Cl2 -> CH3Cl + HCl

d) Classify carbon.

Ans:

Carbon exist in nature in two different forms crystalline and amorphous forms.

Crystalline forms of carbon:

• These are having definite shape due to the periodic arrangement of its atoms.
• These are having long range order of its constituent particles.
• These solids are having sharp and high melting point.
• These are having definite heat of fusion.
• These solids are anisotropic in nature and these are the true solids.

For example: diamond, graphite, fullerenes are the crystalline forms of carbon.

Non crystalline forms of carbon:

• These are having irregular shape with short range order of its constituent particles.
• These solids may melt and soften over certain range of temperature.
• These solids are not having specific heat of fusion due to their irregular shape.
• These solids are isotropic in nature and they are pseudo solids or super cooled liquids.,

For example:

Charcoal, coal, lignite, bituminous, anthracite etc are the amorphous forms of the carbon.

9.) How will you verify the properties of carbon dioxide.

Ans:

By using following chemical methods we can verify the properties of carbon dioxide.

1) By using limewater:

• When a test tube filled with limewater is is inserted in the test tube containing baking soda and lemon juice then limewater turns milky and some effervescence are released which are of the carbon dioxide gas.
• The following chemical reaction shows the formation of carbon dioxide gas.

Ca(OH)2 + CO2 -> CaCO3 + H2O

2) When carbon dioxide is passed through the aqueous solution of sodium hydroxide then sodium carbonate is formed as shown in the following chemical reaction.

2NaOH + CO2 -> Na2CO3 + H2O

3) When carbon dioxide gas is passed through the aqueous solution of sodium carbonate then sodium bicarbonate is formed as shown in the following chemical reaction.

Na2CO3 + H2O + CO2 -> 2NaOHCO3