Question 1

Question 13Starting from carbon dioxide how would you obtain(a) A weak acid(b) A fertilizer(c) A highly poisonous gas(d) Black particles of carbon.[Give balanced equations for the same]

Accepted Answer

(a) CO2 dissolves in water under pressure to give a weak acid called carbonic acid [H2CO3].CO2 + H2O ⟶ H2CO3(b) CO2 reacts with ammonia gas at elevated temperatures & pressures forming Urea [(NH2)2CO], an important nitrogenous fertilizer.2NH3 + CO2 ⟶ (NH2)2CO + H2O(c) CO2 when passed over heated coke [carbon] is reduced to Carbon monoxide [CO] which is a highly poisonous gas.CO2 + C ⟶ 2CO(d) Burning magnesium burns in CO2 producing Magnesium oxide [MgO] & black particles of carbon [C].2Mg + CO2 ⟶ 2MgO + C

Question 2

Question 15'When carbon dioxide is bubbled into lime water, the lime water turns milky and when bubbled in excess the milkiness disappears'. Give balanced equations to support the statement.

Accepted Answer

When carbon dioxide is bubbled into lime water, the lime water turns milky due to the formation of insoluble calcium carbonate.Ca(OH)2 + CO2 ⟶ CaCO3 ↓ + H2OWhen CO2 is bubbled in excess the milkiness disappears due to the formation of soluble calcium bicarbonate [Ca(HCO3)2]CaCO3 + H2O + CO2 ⟶ Ca(HCO3)2

Question 3

Question 18State the function of conc. sulphuric acid in the laboratory preparation of carbon monoxide from oxalic acid.

Accepted Answer

Conc. sulphuric acid acts as a dehydrating agent & removes a molecule of water from oxalic acid to produce carbon monoxide and carbon dioxide. The reaction is given below:HOOC-COOH →Conc. H2SO4\xrightarrow{	ext{Conc. H}_2	ext{SO}_4}Conc. H2​SO4​​ H2O + CO + CO2

Question 4

Question 7(a)Why is graphite a good conductor of electricity but not diamond?

Accepted Answer

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

Question 5

Question 7(c)What are fullerenes? Name the most common fullerene.

Accepted Answer

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

Question 6

Question 9Write three differences between graphite and diamond.

Accepted Answer

GraphiteDiamondGraphite is greyish black, opaque and shiny.Pure diamond is colourless and transparent.Graphite is soft and greasy to touch.Diamond is the hardest naturally occurring substance.Graphite is a good conductor of electricity.Diamond is a bad conductor of electricity.

Question 7

Question 6(a)What is destructive distillation? What are the products formed due to the destructive distillation of coal?

Accepted Answer

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.

Question 8

Question 6(c)How is wood charcoal made locally? What other substances are formed in the process?

Accepted Answer

Locally, wood charcoal is prepared by the following steps:Logs of wood are piled one above the other with a gap in the centre of the pile.The pile is covered with wet clay to prevent the entry of air.A few holes are left at the bottom of the pile.The wood is set on fire.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, pyroligneous acid.

Question 9

Question 7(a)Describe the formation of coal.

Accepted Answer

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

Question 10

Question 7(b)Name four types of coal with the percentage of carbon present in each.

Accepted Answer

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

Question 11

Question 9Give two uses for each of the following:(a) coal(b) coke(c) wood charcoal(d) sugar charcoal(e) bone charcoal(f) lamp black

Accepted Answer

(a) CoalIt is used both as a domestic and industrial fuel.It is used to prepare coke, coal gas and coal tar.(b) CokeIt is used in the manufacture of water gas (CO + H2), producer gas (CO + N2) and artificial graphite.It is used as a smokeless industrial and domestic fuel.(c) Wood charcoalIt is an important constituent of gun powder.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 charcoalIt is used to prepare artificial diamonds.It is used mostly as a reducing agent to extract metals from their respective oxides.(e) Bone charcoalIt is used to decolourise cane sugar in the process of manufacturing sugar.It is used to remove excess of fluoride from water which causes tooth decay.(f) Lamp blackIt is used in making black shoe polish, carbon paper, printing ink, black paint etc.It is used in manufacture of tyres and gun powder.

Question 12

Question 2Write the balanced chemical equations for the preparation of carbon dioxide by:(a) heating calcium carbonate.(b) the action of acetic acid on sodium bicarbonate.(c) the action of dilute sulphuric acid on sodium bicarbonate.(d) the action of dilute hydrochloric acid on sodium carbonate.

Accepted Answer

(a) CaCO3 →Δ\xrightarrow{\enspace\Delta\enspace}Δ​ CaO + CO2 (g)(b) NaHCO3 + CH3COOH ⟶ CH3COONa + H2O + CO2 (g)(c) NaHCO3 + H2SO4 ⟶ NaHSO4 + H2O + CO2(d) Na2CO3 + 2HCl ⟶ 2NaCl + H2O + CO2

Question 13

Question 6Explain the term greenhouse effect. What are its benefits? How is it harmful?

Accepted Answer

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:In colder regions, this principle is applied to grow plants.It makes the surface of 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 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 earth is known as global warming which is harmful. Global warming has serious consequences like:It will cause melting of glaciers and ice in polar regions causing floods.Ecological balance will get disturbed, rainfall patterns will be changed.Pattern of crop cultivation will be changed.Many species of plants and animals will get extinct.

Question 14

Question 7Explain the reducing action of carbon monoxide.

Accepted Answer

Carbon monoxide is a strong reducing agent and it reduces the oxides of moderately or less active metals to their respective metals and itself gets oxidized to carbon dioxide in the process.CuO + CO →Δ\xrightarrow{\enspace\Delta\enspace}Δ​ Cu + CO2

Question 15

Question 9Complete the reactions and balance them.(a) CuO + CO ⟶(b) Fe2O3 + CO ⟶

Accepted Answer

(a) CuO + CO →Δ\xrightarrow{\enspace\Delta\enspace}Δ​ Cu + CO2(b) Fe2O3 + 3CO →Δ\xrightarrow{\enspace\Delta\enspace}Δ​ 2Fe + 3CO2

Question 16

Question 3Give a balanced equation for the following conversions: [In one or two steps]Coke to water gas.Calcium bicarbonate to calcium nitrate using a dilute acidLime water [soln. of calcium hydroxide] to calcium bicarbonate.Carbon dioxide to carbon.A metallic oxide to calcium carbonate.

Accepted Answer

Ccoke+H2Osteam→1000°C[CO+H2]water gas−Δ\underset{	ext{coke}}{	ext{C}} + \underset{	ext{steam}}{	ext{H}_2	ext{O}} \xrightarrow{1000 \degree 	ext{C}} \underset{	ext{water gas}}{[	ext{CO} + 	ext{H}_2 ]} - \DeltacokeC​+steamH2​O​1000°C​water gas[CO+H2​]​−ΔCa(HCO3)2 calcium bicarbonate+2HNO3Dil acid⟶Ca(NO3)2+2CO2+2H2O\underset{	ext{ calcium bicarbonate} }{	ext{Ca}	ext{(HCO}_3)_2} + \underset{	ext{Dil acid}}{2	ext{HNO}_3} \longrightarrow 	ext{Ca(NO}_3)_2 + 2	ext{CO}_2 + 2	ext{H}_2	ext{O} calcium bicarbonateCa(HCO3​)2​​+Dil acid2HNO3​​⟶Ca(NO3​)2​+2CO2​+2H2​OCa(OH)2 + CO2 ⟶ CaCO3 ↓ + H2OCaCO3 + H2O + CO2 ⟶ Ca(HCO3)2CO2 + 2Mg ⟶ 2MgO + CNa2O + CO2 ⟶ Na2CO3

Question 17

Question 5Give reasons for the following:Diamond & graphite are allotropic modifications of carbon.It is dangerous to stand behind a running engine of a vehicle.Both CO2 & SO2 turn lime water milky. Moist potassium permanganate paper, helps in distinguishing the two gases.Carbon monoxide and not carbon dioxide is a highly poisonous gas.Lime water finds application for testing both carbon dioxide & carbon monoxide gas individually.

Accepted Answer

Diamond & graphite are different in atomic arrangement in the crystal structure of the element. Hence they differ in physical properties but are forms of the same element carbon, and hence have similar chemical properties and are called allotropic forms of carbon.It is dangerous to stand behind a running engine of a vehicle since in exhaust fumes carbon monoxide is present due to incomplete combustion of fuel in the engine.SO2 turns potassium permanganate paper from purple to colourless whereas CO2 does not. Hence, the two gases can be distinguished.Carbon monoxide has a very strong affinity for haemoglobin, binding to it about 200-250 times more strongly than oxygen to form a stable compound called carboxyhaemoglobin which prevents the haemoglobin from carrying oxygen efficiently. Carbon dioxide also combines with haemoglobin to form carbaminohaemoglobin but its affinity for haemoglobin is much weaker compared to oxygen and carbon monoxide. This makes carbon monoxide and not carbon dioxide a highly poisonous gas.When carbon dioxide is bubbled into lime water, the lime water turns milky due to the formation of insoluble calcium carbonate.Ca(OH)2 + CO2 ⟶ CaCO3 ↓ + H2OWhen CO2 is bubbled in excess the milkiness disappears due to the formation of soluble calcium bicarbonate [Ca(HCO3)2]CaCO3 + H2O + CO2 ⟶ Ca(HCO3)2On the other hand lime water does not directly react with carbon monoxide.CO + lime water ⟶ No milkiness.However, on ignition, carbon monoxide burns with a pale blue flame forming carbon dioxide which reacts with lime water.

Carbon & Its Compounds

Carbon dioxide

Carbon monoxide

Exercise I

Exercise II

Exercise III

Exercise IV

Objective Type Questions