Carbon & Its Compounds

petroleum

Reason — In combined state, carbon occurs in natural gas and petroleum.
Diamond is pure carbon. Graphite is pure carbon. Coal contains carbon mixed with impurities.

fullerene

Reason — Fullerene is a crystalline form of carbon.
Lamp black is amorphous carbon. Gas carbon is amorphous carbon. Sugar is not an elemental form of carbon.

has high melting point

Reason — Graphite is used to make crucibles because it has a high melting point.

cutting and drilling rocks and glass.

Reason — Diamond is used for cutting and drilling rocks and glass as it is very hard.
Graphite is used in making the electrodes of electric furnaces, crucibles for melting metals, carbon brushes for electric motors.

Both P and R are correct.

Reason — Carbon forms innumerable compounds because carbon atoms have the unique property of linking with one another to form very long chains of different sizes which may be straight, branched or cyclic. This property is called catenation. Carbon has four electrons in its outermost shell.

(a) Carbon

(b) Allotropy

(c) Graphite, Diamond

(d) Diamond

(e) Carbo

(a) True

(b) False
Correct statement — Diamond is the purest form of carbon.

(c) False
Correct statement — Colourless and transparent diamonds are costlier than coloured diamonds.

(d) True

(e) False
Correct statement — Diamond is insoluble in all solvents.

(a) Crystals

(b) Allotropy

(c) Catenation

(a) Diamond

(b) Graphite

(c) Fullerene

60 carbon atoms are there in Buckminster fullerene.

(a) Allotropy is defined as the phenomenon due to which an element exists in two or more forms in the same physical state with identical chemical properties but with different physical properties.

(b) The weight of a diamond is expressed in terms of carats, where 1 carat = 0.2 g.

(c) A crystal is a homogeneous solid in which particles are arranged in a definite pattern due to which they have a definite geometrical shape with a plane surface.

(d) Carbon atoms possess a unique property to link themselves together to form very long chains of different sizes which may be straight, branched or cyclic and this property is called catenation.

(a) In graphite, one valence electron of each carbon atom remains free, so it is a good conductor of electricity. But in diamond there are no free or mobile electrons so it does not conduct electricity.

(b) In diamond, a carbon atom has four valence electrons. Each carbon atom is linked with four neighbouring carbon atoms forming a rigid tetrahedral structure. Due to this strong bonding diamond is very hard.

(c) Fullerenes are the third crystalline allotrope of carbon. In fullerenes, many carbon atoms are held together in a cage-like structure. The most common fullerene is buckminster fullerene or buckyball.

(d) Black diamonds have copper oxide present in them as an impurity.

(a) The two uses of graphite are:

1. Used for making the electrodes of electric furnaces, since graphite is a good conductor of electricity.
2. Used for making crucibles for melting metals due to its high melting point.

(b) The two uses of diamond are:

1. For making jewellery because of its brilliant shine, pure diamond is used in jewellery as a gem.
2. Impure diamond (black diamond) is used for cutting and drilling rocks, glass or other diamonds due to its hard nature.

a superior type of coal

Reason — Anthracite is the purest variety of coal. Its carbon content is between 92-98%.

All of the above

Reason — Destructive distillation of coal produces coke, coal tar, coal gas and ammoniacal solution.

an amorphous form of carbon

Reason — Lamp black is an amorphous form of carbon which contains 98-99% carbon. Lamp black is a form of carbon that does not have a regular crystal structure rest all have specific structure.

carbonization

Reason — The process by which decayed plants slowly convert into coal is called carbonization.
Petrification means turning into stone (fossilization), not specifically forming coal. Fermentation is a biological process involving microorganisms (like making alcohol), not coal formation.

sugar charcoal

Reason — The purest form of amorphous carbon is sugar charcoal.
Wood charcoal contains impurities like ash and volatile substances, so not very pure. Bone charcoal contains calcium phosphate and other impurities. Lamp black contains impurities.

(a) Carbon monoxide

(b) amorphous

(c) Peat

(d) bad

(e) Lamp black (soot)

(a) True

(b) False
Correct statement— Coke is obtained by destructive distillation of coal.

(c) False
Correct statement — Activated charcoal is a bad conductor of electricity.

(d) True

(e) False
Correct statement — Ammoniacal solution is used in the preparation of artificial fertilizers.

(a) Amorphous substances

(b) Anthracite

(c) Sugar charcoal

(d) Coke

(e) Water gas

(a) The process of slow conversion of vegetable matter into carbon-rich substances is called carbonization.

(b) Adsorption is the property due to which a substance adsorbs gases, liquids and solids only on its surface.

(c) When a substance is heated in the absence of air, the process is called destructive distillation. It results in the decomposition of the substance into its constituent substances.

Wood charcoal has high adsorbing capacity, so it is used in water filters to remove impurities and in gas masks to adsorb harmful gases.

(a) Wood charcoal, wood tar, wood gas, pyroligneous acid.

(b) Bone charcoal, bone oil, pyridine.

(c) Carbon dioxide

(d) Artificial diamonds.

(a) Coal

1. It is used both as a domestic and industrial fuel.
2. It is used to prepare coke, coal gas and coal tar.

(b) Coke

1. It is used in the manufacture of water gas (CO + H₂), producer gas (CO + N₂) and artificial graphite.
2. It is used as a smokeless industrial and domestic fuel.

(c) Wood charcoal

1. It is an important constituent of gun powder.
2. Due to its high adsorbing capacity, it is used in military and industrial gas masks to adsorb harmful gases and in water purifier filters.

(d) Sugar charcoal

1. It is used to prepare artificial diamonds.
2. It is used mostly as a reducing agent to extract metals from their respective oxides.

(e) Bone charcoal

1. It is used to decolourise cane sugar in the process of manufacturing sugar.
2. It is used to remove excess of fluoride from water which causes tooth decay.

(f) Lamp black

1. It is used in making black shoe polish, carbon paper, printing ink, black paint etc.
2. It is used in manufacture of tyres and gun powder.

When a substance is heated in the absence of air, the process is called destructive distillation. It results in the decomposition of the substance into its constituent substances. Destructive distillation of coal produces coke, coal tar, coal gas and ammoniacal solution.

Locally, wood charcoal is prepared by the following steps:

1. Logs of wood are piled one above the other with a gap in the centre of the pile.
2. The pile is covered with wet clay to prevent the entry of air.
3. A few holes are left at the bottom of the pile.
4. The wood is set on fire.
5. When the fire dies out a greyish-black, brittle, porous solid is left behind which is wood charcoal.

The other substances formed are wood tar, wood gas and pyroligneous acid.

The process of formation of coal is described below:

1. Coal was formed by the bacterial decomposition of ancient vegetable matter buried under successive layers of the earth.
2. Under the action of high pressure and temperature, in the absence of air, the decayed vegetable matter was converted into coal through a series of steps as shown in the figure below.
3. With each successive layer of coal formed, the amount of carbon present in the deposit increased and the level of impurities decreased.
4. This process of formation of coal is known as carbonization which took millions of years.

The four types of coal are:

1. Peat — It contains about 50 to 60% carbon.
2. Lignite — It contains more than 60% carbon.
3. Bituminous — There are high, medium and low varieties of bituminous coal with carbon content 90%, 80% and 70-75% respectively.
4. Anthracite — It contains 92-98% carbon content.

CO₂

Reason — CO₂ is a greenhouse gas. It traps some of the heat coming from Earth and helps keep our planet warm.
O₂ is needed for respiration, but does not trap heat significantly. N₂ is a major component of air, but does not contribute to warming. Ne is an inert gas but has no role in warming.

dil. hydrochloric acid

Reason — The acid used in the laboratory preparation of carbon dioxide gas is dil. hydrochloric acid.
Conc. sulphuric acid forms a coating of calcium sulphate on the marble chips, stopping the reaction. Dil. sulphuric acid forms calcium sulphate (insoluble), which slows/stops the reaction. Conc. hydrochloric acid is too strong and not typically used in lab preparation; dilute acid is preferred for controlled reaction.

Magnesium

Reason — Magnesium metal burns in the presence of carbon dioxide to give magnesium oxide and carbon (black).
Iron does not burn in carbon dioxide because it is not reactive enough to take oxygen from CO₂. Aluminium does not burn in carbon dioxide because it is covered by a protective oxide layer (Al₂O₃). Copper is even less reactive as it cannot take oxygen from CO₂ at all.

carbogen

Reason — A mixture of 5% carbon dioxide and 95% oxygen, called carbogen, is used for artificial respiration.
Carbon is an element; it is not used in respiration. Carbon dioxide alone is not used because excess CO₂ can be harmful. Carbonization is the slow process by which dead plant material turns into coal.

dry ice

Reason — Dry ice is a sublimable substance, and it directly changes into gaseous carbon dioxide, from its solid state, i.e., without passing through its liquid state.
Sodium bicarbonate does not sublime; it decomposes on heating instead. Marble does not sublime; it decomposes at high temperature. Lime water is a liquid, so it cannot sublime.

(a) CaCO₃ $\xrightarrow{\enspace\Delta\enspace}$ CaO + CO₂ (g)

(b) NaHCO₃ + CH₃COOH ⟶ CH₃COONa + H₂O + CO₂ (g)

(c) 2NaHCO₃ + H₂SO₄ ⟶ Na₂SO₄ + 2H₂O + 2CO₂

(d) Na₂CO₃ + 2HCl ⟶ 2NaCl + H₂O + CO₂

(a) When a lit splinter is introduced into a jar containing carbon dioxide, it extinguishes as carbon dioxide is a non-supporter of combustion.

(b) Carbon dioxide turns moist blue litmus red. This shows that the gas is acidic in nature.

(c) When carbon dioxide is passed through lime water first in small amounts it turns lime water milky. This is due to the formation of insoluble calcium carbonate. When excess of the gas is passed through the solution milkiness disappears. This is due to the formation of soluble calcium bicarbonate.

(d) Baking soda, i.e., sodium bicarbonate reacts with vinegar (acetic acid) to form sodium acetate, water, and releases carbon dioxide gas.

(e) Carbon dioxide gas is dissolved in water under pressure to give soda water. When a soda water bottle is opened, the pressure is released and the bottled gas escapes with a brisk effervescence that adds a fizz to the drink.

Carbon dioxide gas traps the long-wave radiations reflected by the earth and keeps our earth warm. But due to air pollution and deforestation excess carbon dioxide gas is emitted and, along with other greenhouse gases, has created a thermal blanket around the earth, trapping more heat and thus the temperature of the earth increases.

In both soda-acid and foam-type of fire extinguishers, the solutions are prepared in water which conducts electricity. As a result, it may generate an electric shock leading to short circuit and another fire.

Solid carbon dioxide (dry ice) serves as a coolant and a refrigerant so it is used for the refrigeration of food like fruits, vegetables, meat, etc. which otherwise perish easily.

(a) The chemicals required for the preparation of carbon dioxide in the laboratory are:

1. Marble chips (CaCO₃)
2. Dilute hydrochloric acid

(b) CaCO₃ + 2HCl ⟶ CaCl₂ + H₂O + CO₂ (g)

(c) The gas is collected by the upward displacement of air.

(d) Laboratory preparation of carbon dioxide :

(e) Dilute sulphuric acid when reacts with marble chips (CaCO₃) forms calcium sulphate. It is insoluble in water so it covers the marble chips and stops the reaction.

CaCO₃ + H₂SO₄ ⟶ CaSO₄ + H₂O + CO₂ (g)

(f) When carbon dioxide is passed through limewater, the latter turns milky and when excess of gas is passed through the solution, milkiness disappears. This test is often used to check for the presence of carbon dioxide gas.

Fire extinguishers are devices in which carbon dioxide is produced in different forms to be used as an extinguishing agent.

Liquid carbon dioxide is the substance used in the modern type of fire extinguishers.

Modern type of fire extinguisher is an improvement over the soda-acid and foam-type fire extinguishers in the following ways:

1. Soda-acid fire extinguishers cannot be used for oil fire as the solution ejected being heavier than oil sinks below oil and does not work whereas modern type of fire extinguishers can be used to put out both oil-fed fires and electrical fires.
2. Both the soda-acid and foam-type fire extinguishers solutions are prepared in water which conducts electricity. It might generate an electric shock leading to short circuit and another fire. But in modern type fire extinguishers, liquid carbon dioxide is used which does not conduct electricity. So, it can be used to put out electrical fires.

The trapping of the earth's radiated energy by carbon dioxide present in the air so as to keep the earth warm is called the greenhouse effect.

Benefits of greenhouse effect are:

1. In colder regions, this principle is applied to grow plants.
2. It makes the surface of the earth warm which provides a suitable environment for survival of living organisms.

Due to deforestation and air pollution, the total amount of carbon dioxide in the air has increased. Carbon dioxide gas along with other greenhouse gases have created a thermal blanket around the earth, trapping more heat and increasing the greenhouse effect. This further warming of the earth is known as global warming, which is harmful. Global warming has serious consequences like:

1. It will cause melting of glaciers and ice in polar regions causing floods.
2. Ecological balance will get disturbed, rainfall patterns will be changed.
3. Pattern of crop cultivation will be changed.
4. Many species of plants and animals will get extinct.

The three ways by which carbon dioxide gas is added into the atmosphere are:

1. Combustion of fuels.
2. Respiration of human beings, animals and plants.
3. By volcanic eruptions.

The steps taken to balance carbon dioxide in the atmosphere are:

1. Growing more trees and plants.
2. Reducing the consumption of fossil fuels.
3. Using filters in the chimneys of factories and power houses.
4. Using smokeless sources of energy like solar energy, biogas etc.

(a) Carbon monoxide

(b) pale blue

(c) incomplete

(d) carbogen

(e) reducing agent

Both A and R are true and R is the correct explanation of A.

Explanation — A is true as carbon Carbon forms a huge number of compounds and is studied under organic chemistry. R is true as carbon atoms can form a large number of compounds because carbon can form long chains with each other.

Therefore, Both A and R are true and R is the correct explanation of A is the correct answer.

Both A and R are true but R is not the correct explanation of A.

Explanation — A is true as coal is rich in carbon and releases a large amount of heat on burning.
R is true as coal is an amorphous form of carbon, but this is not the reason why coal is used as a fuel.

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

A is true but R is false.

Explanation — A is true as diamond and graphite are crystalline allotropes of carbon. R is false as diamond is a bad conductor of electricity because it has no free or mobile electrons, but it is used for making gems. Graphite is a good conductor of electricity, but it is not used for making gems.

Therefore, A is true but R is false is the correct option.

Both A and R are true and R is the correct explanation of A.

Explanation — A is true as an increase in the impurities means lesser clarity of diamonds, which reduces their value.
R is true as colourless, transparent diamonds are the costliest as they are used for making gems and various jewellery.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Both A and R are true and R is the correct explanation of A.

Explanation — A is true as pencil leads are made up of graphite.
R is true as graphite leaves a black mark on paper.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Both A and R are true and R is the correct explanation of A.

Explanation — A is true as carbon dioxide is used in fire extinguishers.
R is true as CO₂ gas cuts off the supply of oxygen to fire, thus helping to extinguish it.

Therefore, Both A and R are true and R is the correct explanation of A is the correct option.

Both A and R are true but R is not the correct explanation of A.

Explanation — A is true as carbon monoxide is an extremely poisonous gas because carbon monoxide combines with the haemoglobin present in the red blood cells of our body to form a stable compound called carboxyhaemoglobin.
R is true as this stable compound does not allow haemoglobin to absorb or carry oxygen, thus depriving our body cells of oxygen. This causes paralysis of the respiratory organs and results in death due to suffocation (asphyxiation).

Therefore, Both A and R are true but R is not the correct explanation of A is the correct option.

Carbon monoxide gas is formed from:

1. Incomplete burning of fuels
2. Exhaust gases of automobiles.

Carbon monoxide is a product of incomplete burning or combustion of carbon and fuels.

2C + O₂ $\xrightarrow{\enspace\Delta\enspace}$ 2CO

Carbon monoxide is used in the extraction of metals from their ores.

The two remedies for carbon monoxide poisoning are:

1. The victim should be given artificial respiration with carbogen to restore normal breathing.
2. The victim should be immediately brought out into the open.

(a) CuO + CO $\xrightarrow {\text{heat}}$ Cu + CO₂

(b) Fe₂O₃ + 3CO $\xrightarrow {\text{heat}}$ 2Fe + 3CO₂

1. Carbon monoxide is a highly poisonous gas. Air containing 0.5% carbon monoxide by volume if inhaled could result in death.
2. Carbon monoxide combines with haemoglobin present in RBCs of our body to form a stable compound carboxyhaemoglobin.
3. This stable compound does not allow haemoglobin to absorb or carry oxygen, thus our body cells get deprived of oxygen. This causes paralysis of respiratory organs and results in death due to suffocation.

It is very dangerous to sleep in a room where coal or wood is burning and its doors and windows are closed. Owing to the limited supply of air in such a room, carbon monoxide is produced. Since the gas is colourless and has a barely detectable smell, people sleeping in the room do not feel its presence and run the risk of carbon monoxide poisoning. That is why carbon monoxide is also called a silent killer.

Carbon monoxide (CO) acts as a reducing agent because it removes oxygen from metal oxides. In doing so, the metal oxide is reduced to the metal, while CO is oxidised to carbon dioxide (CO₂).

Example:

CuO + CO $\xrightarrow{\enspace\Delta\enspace}$ Cu + CO₂

Here, CuO loses oxygen (so it is reduced to Cu) and CO gains oxygen (so it is oxidised to CO₂).

(a) The gas released by fire extinguishers is carbon dioxide.

(b) Carbon dioxide helps to put out fire by:

1. Cutting off oxygen supply as fire needs oxygen to burn.
2. Forming a blanket over the fire, which prevents further burning.

(c) Types of fire extinguishers used are:

(i) Oil fire: Foam fire extinguisher

(ii) Electrical fire: Carbon dioxide fire extinguisher

(d) It is dangerous to use water on an electrical fire because of the following reasons:

1. Water is a good conductor of electricity.
2. It can cause electric shock to the person using it.
3. It may also spread the fire if live current is present.