CBSE Class 10 Science Carbon And Its Compounds Worksheet Set G

Multiple Choice Questions

Question. While studying the saponification reaction, what do you observe when you mix an equal amount of colourless vegetable oil and 20% aqueous solution of \( \text{NaOH} \) in a beaker ?
(a) The colour of the mixture has become dark brown.
(b) A brisk effervescence is taking place in the beaker.
(c) The outer surface of the beaker has become hot.
(d) The outer surface of the beaker has become cold.
Answer: (c)

Question. You have four test tubes A, B, C and D filled with aqueous solution of same concentration but of different salts. In A solution of \( \text{NaCl} \), B solution of \( \text{CaCl}_2 \), C solution of \( \text{MgCl}_2 \) and D solution of \( \text{KCl} \) is filled. If you add equal amounts of a soap solution to each test tube and shake the contents well, in which of the test tubes will scum (insoluble substance) be obtained ?
(a) A and B
(b) B and C
(c) C and D
(d) A and D
Answer: (b)

Question. Select the correct statement about the properties of acetic acid.
(a) It smells like vinegar and turns red litmus to blue.
(b) It is insoluble in water and turns blue litmus to red.
(c) It is soluble in water and turns red litmus to blue.
(d) It smells like vinegar and turns blue litmus to red.
Answer: (d)

Question. You have neem oil in a beaker. In order to study saponification reaction, which of the following chemical substances would you add to this oil ?
(a) 20% \( \text{Ca(OH)}_2 \)
(b) 20% \( \text{NaOH} \)
(c) 30% \( \text{Mg(OH)}_2 \)
(d) 10% \( \text{Ca(OH)}_2 \)
Answer: (b)

Question. Some students studied the physical properties of acetic acid and noted down their observations. Which of the following observations is correct ?
(a) Smells like rose and soluble in water.
(b) Smells like burning plastic and insoluble in water.
(c) Smells like vinegar and soluble in water.
(d) Smells like rotten egg and soluble in water.
Answer: (c)

Question. A student wants to prepare soap in the laboratory. Which of the following sets of materials he should use ?
(a) Neem oil and \( \text{NaCl} \)
(b) Neem oil and \( \text{Na}_2\text{CO}_3 \)
(c) Mustard oil and \( \text{NaOH} \)
(d) Mineral oil and \( \text{NaOH} \)
Answer: (c)

Question. You are asked to prepare hard water in your laboratory. Select a group from the following groups of salts, any salt of which you may dissolve in distilled water to obtain hard water.
(a) \( \text{NaCl; Na}_2\text{SO}_4\text{; KCl} \)
(b) \( \text{NaCl; CaCl}_2\text{; KCl} \)
(c) \( \text{CaCl}_2\text{; CaSO}_4\text{; MgSO}_4 \)
(d) \( \text{Na}_2\text{SO}_4\text{; CaSO}_4\text{; MgSO}_4 \)
Answer: (c)

Question. The chemical mostly used in the preparation of most of the soaps we use is :
(a) Sodium chloride
(b) Potassium hydroxide
(c) Sodium hydroxide
(d) Potassium chloride
Answer: (c)

Question. A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from :
(a) rain
(b) tap
(c) hand pump
(d) pond
Answer: (a)

Question. Which of the following does not belong to the same homologous series ?
(a) \( \text{CH}_2 \)
(b) \( \text{C}_2\text{H}_6 \)
(c) \( \text{C}_3\text{H}_8 \)
(d) \( \text{C}_4\text{H}_8 \)
Answer: (d)

Question. The name of the compound \( \text{CH}_3\text{— CH}_2\text{— CHO} \) is :
(a) Propanal
(b) Propanone
(c) Ethanol
(d) Ethanal
Answer: (a)

Question. The hetero-atoms present in \( \text{CH}_3 \text{ — CH}_2 \text{ — O — CH}_2 \text{ —CH}_2\text{Cl} \) is :
(i) Oxygen (ii) Carbon (iii) Hydrogen (iv) Chlorine
(a) (i) and (ii)
(b) (ii) and (iii)
(c) (iii) and (iv)
(d) (i) and (iv)
Answer: (d)

Question. The first member of alkyne homologous series is :
(a) Ethyne
(b) Ethene
(c) Propyne
(d) Methane
Answer: (a)

Question. The bond between two identical non-metallic atom has a pair of electron :
(a) unequally shared between two atoms.
(b) transferred completely from one atom to another.
(c) with identical spins.
(d) equally shared between them.
Answer: (d)

Question. Match the following
Column-I
(a) Cyclohexane
(b) Methanol
(c) Acetaldehyde
(d) Ethanoic acid

Column-II
(i) \( \text{CH}_3\text{COOH} \)
(ii) \( \text{CH}_3\text{Cl} \)
(iii) \( \text{CH}_2\text{Cl}_2 \)
(iv) \( \text{CH}_3\text{OH} \)
(v) \( \text{C}_6\text{H}_{12} \)
(vi) \( \text{CH}_3\text{CHO} \)
Answer: (a) (v), (b) (iv), (c) (vi), (d) (i).

Fill in the blanks

Question. (a) The organic compounds having double or triple bonds in them are termed as .................. .
(b) Consecutive members of a homologous series differ by .................. group.
(c) .................. is the general formula of alkene.
Answer: (a) Unsaturated compounds, (b) \( \text{— CH}_2 \), (c) \( \text{C}_n\text{H}_{2n} \).

Very Short Answers Type Questions

Question. Write the molecular formula of ethene and draw its electron dot structure.
Answer: Molecular formula of ethene is \( \text{C}_2\text{H}_4 \).
Electron dot structure of ethene :
\[ \text{H} \cdot \cdot \text{C} :: \text{C} \cdot \cdot \text{H} \]
Or \( \text{CH}_2 = \text{CH}_2 \)

Question. Draw electron dot structure of carbon dioxide and write the nature of bonding between carbon and oxygen in its molecule.
Answer: \( \text{:}\ddot{\text{O}}\text{::C::}\ddot{\text{O}}\text{:} \) or \( \text{O = C = O} \)
Covalent bond (double bond) is present in between C and O.

Question. List two properties of carbon which lead to the huge number of carbon compounds we see around us, giving reason for each.
Answer: Two properties of carbon which lead to the huge number of carbon compounds are :
(a) Catenation : It is the ability of carbon to form bonds with other atoms of carbon.
(b) Tetravalency : With the valency of four, carbon is capable of bonding with 4 other atoms. This forms huge number of compounds.

Question. List two chemical properties on the basis of which ethanol and ethanoic acid may be differentiated and explain how.
Unsaturated hydrocarbons contain multiple bonds between two carbon atoms and these compounds show addition reactions. Out of saturated and unsaturated carbon compounds, which compounds are more reactive ? Write a test to distinguish ethane from ethene.
Answer: (a) Ethanol does not react with sodium bicarbonate but ethanoic acid reacts with sodium bicarbonate releasing \( \text{CO}_2 \) gas.
(b) Ethanol does not change the colour of blue litmus paper but ethanoic acid changes the colour of blue litmus to red due to presence of carboxylic acid group.
Unsaturated carbon compounds are more reactive than saturated carbon compounds. Bromine water is decolourised by ethene but there is no change of colour of bromine water with ethane.

Question. In three test tubes A, B and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap solution is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest ? Justify your answer.
Answer: Length of foam would be longest in test tube A. It is because it does not have any ions, so length of the foam would be longest.

Question. Write the molecular formula of the \( 2^{\text{nd}} \) and the \( 3^{\text{rd}} \) member of the homologous series whose first member is methane.
Answer: (a) Ethane \( \text{C}_2\text{H}_6 \)
(b) Propane \( \text{C}_3\text{H}_8 \)

Question. Write the molecular formula of the \( 2^{\text{nd}} \) and \( 3^{\text{rd}} \) member of the homologous series whose first member is ethene.
Answer: (a) Propene : \( \text{C}_3\text{H}_6 \)
(b) Butene : \( \text{C}_4\text{H}_8 \)

Question. Write the molecular formula of the \( 2^{\text{nd}} \) and \( 3^{\text{rd}} \) member of the homologous series where the first member is ethyne.
Answer: (a) \( \text{CH}_3\text{C ≡ CH} \) (propyne), \( n = 3 \)
(b) \( \text{CH}_3\text{CH}_2\text{C ≡ CH} \) (Butyne), \( n = 4 \)

Question. Write the molecular formula of first two members of homologous series having functional group-Cl.
Answer: The general formula for the homologous series of functional group –Cl is \( \text{C}_n\text{H}_{2n+1}\text{Cl} \).
(a) \( \text{CH}_3\text{Cl} \)
(b) \( \text{CH}_3\text{CH}_2\text{Cl} \)

Question. Write the molecular formula of first two members of homologous series having functional group -Br.
Answer: General formula for the homologous series of Br group is \( \text{C}_n\text{H}_{2n+1}\text{Br} \).
(a) \( \text{CH}_3\text{Br} \) (Bromomethane)
(b) \( \text{CH}_3\text{CH}_2\text{Br} \) (Bromoethane)

Question. Write the molecular formula of first two members of homologous series having functional group-OH.
Answer: The general formula for the homologous series of functional group-OH is \( \text{C}_n\text{H}_{2n+1}\text{OH} \)
(a) \( \text{CH}_3\text{OH} \) (Methanol)
(b) \( \text{CH}_3\text{CH}_2\text{OH} \) (Ethanol)

Question. Name the black substance of pencil.
Answer: Graphite.

Question. Out of butter and ground nut oil, which is unsaturated in nature ?
Answer: Groundnut oil is unsaturated in nature.

Question. Which substance is added to denature ethyl alcohol ?
Answer: A small amount of methyl alcohol, pyridine or copper sulphate is added to denature ethyl alcohol.

Question. Why is fullerene so called ?
Answer: Fullerene is so called because it resembles the framework of dome shaped halls designed by American architect Buckminster fuller.

Question. Hard water do not produce foam with soap easily. Why ?
Answer: Due to the presence of calcium and magnesium salts hard water does not produce foam with soap easily.

Question. Write the name of the following :
(a) \( \text{CH}_2 = \text{CH}_2 \)
(b) \( \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{CH}_3 \)
(c) \( \text{CH}_3\text{CHBrCH}_3 \)
(d) \( \text{CH}_3\text{CH = CHCHCH}_3\text{Cl} \)
(e) \( \text{CH}_3\text{CH = CHCHO} \)
Answer: (a) Ethene (b) Pentane (c) Bromopropane (d) 4-chloro-2-pentene (e) Pent-2-en-1-al

Question. Draw the structure of the following :
(a) Propanoic acid (b) 2-propanol
(c) 1-Iodopropane (d) 3-chlorobutanone
(e) Propyne
Answer: (a) \( \text{CH}_3\text{CH}_2\text{COOH} \) (b) \( \text{CH}_3\text{CH(OH)CH}_3 \) (c) \( \text{CH}_3\text{CH}_2\text{CH}_2\text{I} \) (d) \( \text{CH}_3\text{CH(Cl)COCH}_3 \) (e) \( \text{CH}_3\text{C ≡ CH} \)

Question. How would you name the following compounds ?
(a) \( \text{CH}_3 \text{ — CH}_2 \text{ — Br} \)
(b) \( \text{H — CHO} \)
(c) \( \text{CH}_3 \text{ — C ≡ C — CH}_2 \text{ — CH}_2 \text{ — CH}_3 \)
Answer: (a) Bromoethane (b) Methanal (c) Hex-2-yne

Question. Write the structural formulae of all the isomers of hexane.
Answer: (a) \( \text{CH}_3\text{—CH}_2\text{—CH}_2\text{—CH}_2\text{—CH}_2\text{—CH}_3 \)
(b) \( \text{CH}_3\text{—CH(CH}_3\text{)—CH}_2\text{—CH}_2\text{—CH}_3 \)
(c) \( \text{CH}_3\text{—CH}_2\text{—CH(CH}_3\text{)—CH}_2\text{—CH}_3 \)
(d) \( \text{CH}_3\text{—C(CH}_3\text{)}_2\text{—CH}_2\text{—CH}_3 \)
(e) \( \text{CH}_3\text{—CH(CH}_3\text{)—CH(CH}_3\text{)—CH}_3 \)

Question. Take about 3 ml of ethanol in a test tube and warm it gently in a water bath. What happens when 5% solution of alkaline potassium permanganate drop by drop is added to this ?
Answer: When potassium permanganate is added drop by drop then its colour disappears initially but more of it is added, the colour will remain as such.

Question. How does Acetic acid smells like ?
Answer: Acetic acid smells like vinegar.

Question. What will be formed when ethanoic acid reacts with sodium bicarbonate ?
Answer: Sodium ethanoate, water and carbon dioxide.

Question. Carbon has four electrons in its valence shell. Which type of compounds can be formed by carbon atom and why ? Give any one example of such compounds.
Answer: Covalent compounds can be formed by carbon atom because carbon atom has 4 valence electrons, hence it is not able to gain four electrons or form \( \text{C}^{4–} \) ion or lose four electrons or form \( \text{C}^{4+} \) ion to attain noble gas configuration. So, it shares electrons to form covalent bonds and the covalent compounds. Example : \( \text{CH}_4 \) (methane) compounds.

Question. In a school laboratory the students are studying the properties of ethanoic acid through certain experiments. How can they test its acidic nature ? Give two tests.
Answer: (a) Blue litmus turns red.
(b) On adding solid sodium carbonate or sodium hydrogen carbonate, brisk effervescence is observed.

Question. If you add a few drops of acetic acid to a test tube containing (i) distillated water and (ii) aqueous solution of sodium hydrogen carbonate, what would you observe ? If a reaction takes place in any one of the above two cases, list its two observations.
Answer: (a) No reaction with distilled water.
(b) Chemical reaction occurs with solution of \( \text{NaHCO}_3 \).
Two observations are :
(i) Evolution of a colourless, odourless gas.
(ii) The gas is evolved with brisk effervescence.

Question. Write the molecular formula of (a) Methane and (b) Ethanol.
Answer: (a) \( \text{CH}_4 \) (b) \( \text{C}_2\text{H}_5\text{OH} \) or \( \text{C}_2\text{H}_6\text{O} \)

Question. You have four beakers A, B, C and D. Out of A and B one has hard water and the other has soft water. Out of C and D one has soap solution and the other has detergent-solution. How would you identify these liquids ?
Answer: On adding soap solution lather will be formed in the beaker containing soft water only. While On adding detergent solution lather will be formed by both hard and soft water in both the beakers.

Question. What do you observe when you add sodium bicarbonate to acetic acid ? How would you identify the gas released in the reaction ? Describe briefly.
Answer: A colourless gas with brisk effervescence will be evolved which turns the lime water milky. When this gas is passed through it.

Question. Write the molecular formula of (a) ethane and (b) ethanoic acid
Answer: (a) \( \text{C}_2\text{H}_6 \)
(b) \( \text{CH}_3\text{COOH} \)

Question. Write the name of (a) \( \text{CH}_4 \) and (b) \( \text{CH}_3\text{COOH} \).
Answer: (a) Methane (b) Ethanoic acid or Acetic acid

Question. Write the molecular formula of the first two members of the homologous series having functional group –COOH.
Answer: \( \text{HCOOH} \) and \( \text{CH}_3\text{COOH} \)

Question. Write the molecular formula of the first two members of the homologous series having functional group C = O.
Answer: \( \text{CH}_3\text{COCH}_3 \) and \( \text{CH}_3\text{COC}_2\text{H}_5 \).

Question. Which element exhibits the property of catenation to maximum extent and why ?
Answer: Carbon exhibits the property of catenation to maximum extent because of strong C—C bond.

Question. Write the name and molecular formula of the fourth member of alkane series.
Answer: Name : Butane, Molecular Formula : \( \text{C}_4\text{H}_{10} \).

Short Answers Type Questions

Question. Which compounds are called (a) alkanes, (b) alkenes and (c) alkynes ? \( \text{C}_4\text{H}_{10} \) belongs to which of these ? Draw two structural isomers of this compound.
Answer: (a) The hydrocarbons in which carbon atoms are connected by only single covalent bonds are called alkanes.
(b) The hydrocarbons in which carbon atoms are connected by double bond are called alkene.
(c) The hydrocarbons in which carbon atoms are connected by triple bond are called alkynes.
\( \text{C}_4\text{H}_{10} \) belongs to alkane.
Structural Isomers of \( \text{C}_4\text{H}_{10} \):
(i) \( \text{CH}_3\text{—CH}_2\text{—CH}_2\text{—CH}_3 \) (ii) \( \text{CH}_3\text{—CH(CH}_3\text{)—CH}_3 \)

Question. A compound ‘X’ on heating with excess conc. sulphuric acid at 443 K gives an unsaturated compound ‘Y’. ‘X’ also reacts with sodium metal to evolve a colourless gas ‘Z’. Identify ‘X’, ‘Y’ and ‘Z’. Write the equation of the chemical reaction of formation of ‘Y’ and also write the role of sulphuric acid in the reaction.
Answer: \( \text{X} = \) Ethanol (\( \text{C}_2\text{H}_5\text{OH} \)), \( \text{Y} = \) Ethene (\( \text{C}_2\text{H}_4 \)), \( \text{Z} = \) Hydrogen (\( \text{H}_2 \)).
Equation: \( \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4, 443\text{K}} \text{C}_2\text{H}_4 + \text{H}_2\text{O} \).
Sulphuric acid acts as a dehydrating agent and removes a molecule of water from ethanol to give ethene.

Question. (a) Why are most carbon compounds poor conductors of electricity ?
(b) Write the name and structure of a saturated compound in which the carbon atoms are arranged in a ring. Give the number of single bonds present in this compound.
Answer: (a) Carbon compounds are covalently bonded and hence the bond is formed by sharing of electrons between two or more combining atoms. Due to this, they don't form any ions or charged particles within the solution nor they give free electrons. As we know, conduction of electricity requires flow of free electrons in solids & ions in liquids, they don't conduct electricity.
(b) Name of the structure : Cyclopropane. Structure is a triangle of \( \text{CH}_2 \) groups. Number of single bonds : 9 single covalent bonds.

Question. Write the structural formula of ethanol. What happens when it is heated with excess of conc. \( \text{H}_2\text{SO}_4 \) at 443 K ? Write the chemical equation for the reaction stating the role of conc. \( \text{H}_2\text{SO}_4 \) in this reaction.
Answer: Structural formula of ethanol is : \( \text{CH}_3\text{CH}_2\text{OH} \). When ethanol is heated with excess of conc. \( \text{H}_2\text{SO}_4 \) at 443 K it results in the dehydration of ethanol to give ethene.
\( \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4, 443\text{K}} \text{CH}_2 = \text{CH}_2 + \text{H}_2\text{O} \).
Role of conc. \( \text{H}_2\text{SO}_4 \) : Conc. \( \text{H}_2\text{SO}_4 \) acts as a dehydrating agent which removes water from the ethanol.

Question. Distinguish between esterification and saponification reaction with the help of the chemical equations for each. State one use of each (a) esters, and (b) saponification process.
Answer: Esterification is opposite of saponification. In esterification : \( \text{RCOOH + R’OH} \xrightarrow{\Delta} \text{RCOOR’ + H}_2\text{O} \). Whereas in saponification : \( \text{RCOOR’ + NaOH} \rightarrow \text{RCOONa + R’OH} \).
(a) Uses of Esters : Esters are used in making perfumes.
(b) Uses of saponification reaction : Used in making soaps and soap products on a large scale.

Question. Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.
Answer: The essential chemicals required to prepare soap in the laboratory are oil and sodium hydroxide solution. In order to determine the nature of the reaction mixture of saponification reaction, we dip red litmus paper into it which will turn blue after a while indicating that it is a basic mixture.

Question. What happens when (write chemical equation in each case)
(a) ethanol is burnt in air ?
(b) ethanol is heated with excess conc. \( \text{H}_2\text{SO}_4 \) at 443 K ?
(c) a piece of sodium is dropped into ethanol ?
Answer: (a) \( \text{CH}_3\text{CH}_2\text{OH} + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O} + \text{Heat + light} \)
(b) \( \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4, 443\text{K}} \text{CH}_2 = \text{CH}_2 + \text{H}_2\text{O} \)
(c) \( 2\text{CH}_3\text{CH}_2\text{OH} + 2\text{Na} \rightarrow 2\text{CH}_3\text{CH}_2\text{ONa} + \text{H}_2\uparrow \)

Question. Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.
Answer: The reaction of carboxylic acid with alcohol forms an ester. This process of formation of ester is called esterification. \( \text{CH}_3\text{COOH} + \text{CH}_3\text{CH}_2\text{OH} \rightarrow \text{CH}_3\text{COOCH}_2\text{CH}_3 + \text{H}_2\text{O} \). Activity: (a) Take 1 ml of ethanol and 1 ml of glacial acetic acid in a boiling tube and mix well. (b) Add few drops of conc. \( \text{H}_2\text{SO}_4 \) to it. (c) Warm the contents on a water bath for a few minutes. (d) Pour solution in a beaker containing 20-50 ml of water. (e) A sweet fruity smell indicating formation of an ester is observed.

Question. Two carbon compounds X and Y have the molecular formula \( \text{C}_4\text{H}_8 \) and \( \text{C}_5\text{H}_{12} \) respectively. Which one of these is most likely to show addition reaction ? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer: \( \text{X = C}_4\text{H}_8 \) is an alkene. \( \text{Y = C}_5\text{H}_{12} \) is an alkane. X being an alkene i.e., butene is unsaturated compound and will show addition reaction as they have free electrons for bonding.
\( \text{CH}_3\text{CH}_2\text{CH = CH}_2 + \text{H}_2 \xrightarrow{\text{Pd/Ni}} \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3 \)
\( \text{CH}_3\text{CH = CHCH}_3 + \text{Cl}_2 \xrightarrow{hv} \text{CH}_3\text{ClCHClCHCH}_3 \)

Question. Two carbon compounds X and Y have the molecular formula \( \text{C}_3\text{H}_6 \) and \( \text{C}_4\text{H}_{10} \) respectively. Which one of the two is most likely to show addition reaction ? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer: \( \text{C}_3\text{H}_6 \) is propene i.e., unsaturated hydrocarbon. \( \text{C}_4\text{H}_{10} \) is butane i.e., saturated hydrocarbon. Thus, propene being unsaturated shows addition reaction.
\( \text{CH}_3 \text{ — CH = CH}_2 + \text{Cl}_2 \rightarrow \text{CH}_3\text{CH(Cl)} \text{ — CH}_2\text{Cl} \)

Question. The molecular formula of two carbon compounds are \( \text{C}_4\text{H}_8 \) and \( \text{C}_3\text{H}_8 \). Which one of the two is most likely to show addition reaction ? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer: (a) \( \text{C}_4\text{H}_8 \) : Butene- alkene (unsaturated hydrocarbon). (b) \( \text{C}_3\text{H}_8 \) : propane-alkane (saturated hydrocarbon). \( \text{C}_4\text{H}_8 \) i.e., butene shows addition reaction as it is unsaturated hydrocarbon. Structure of butene reacting with \( \text{Cl}_2 \) leads to 1,2-dichlorobutane.

Question. Why does micelle formation takes place when soap is added to water ? Will a micelle form in other solvents such as ethanol also ?
Answer: Soap may be represented by the formula \( \text{RCOONa} \) where R is an alkyl group which represents long chain of carbon. Oil drops and water do not mix. Soap helps in their mixing by reducing interfacial tension. Actually it forms a sort of bridge between oil drops and water in which the alkyl portion (hydrophobic end) point towards oil drop while other portion (hydrophilic end) is directed towards water. This is known as micelle formation. Ethanol and other similar solvents which are of organic nature do not help in micelle formation because soap is soluble in them.

Question. Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Compare the ability of catenation of the two elements. Give reasons.
Answer: Carbon has the maximum capacity of catenation. The reason for this is the smaller size of carbon which makes the C–C bonds strong. The size of silicon is greater than Carbon. This makes Si—Si bonds comparatively weaker than C – C bond.

Question. (a) What is the atomic number of carbon. Write its electronic configuration.
(b) What type of chemical bonds are formed by carbon ? Why ?
(c) Name the three allotropic forms of carbon.
Answer: (a) The atomic number of carbon is 6. Its electronic configuration is 2, 4.
(b) Carbon forms covalent bonds because it can achieve the inert gas electron arrangement only by sharing of electrons.
(c) Diamond, graphite and buckminster fullerene.

Question. (a) Give the general name of the class of compounds having the general formula \( \text{C}_n\text{H}_{2n–2} \). Write name of the first member of this homologous series.
(b) The general formula of a homologous series of carbon compounds is \( \text{C}_n\text{H}_{2n} \). Write the molecular formulae of the second and fifth members of the series.
(c) Write the molecular formulae of the third and fourth members of homologous series of carbon compounds represented by the general formula \( \text{C}_n\text{H}_{2n+2} \).
Answer: (a) Alkynes, \( \text{C}_n\text{H}_{2n–2} \). First member : Ethyne : \( \text{C}_2\text{H}_2 \). (b) Second member : \( \text{C}_3\text{H}_6 \). Fifth member : \( \text{C}_6\text{H}_{12} \). (c) Third member : \( \text{C}_3\text{H}_8 \). Fourth member : \( \text{C}_4\text{H}_{10} \).

Question. Preetam and Satnam were revising the chapter on Carbon and its compounds. Preetam said, “It is quite amazing that diamond and graphite are both allotropes of carbon but the two have completely different properties. While diamond is the hardest material, graphite is soft”.
(a) What is the cause of different nature of these two substances ?
(b) What is the core of lead pencils ?
Answer: (a) The difference in nature is due to structure. In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three dimensional structure. In graphite, each carbon atom is bonded to three other carbon atoms in the same plane, giving a hexagonal array.
(b) Lead pencil core is made of graphite.

Question. What is hydrogenation ? What is its industrial application ?
Answer: Hydrogenation is the process of addition of hydrogen. Unsaturated hydrocarbons are added with hydrogen in the presence of palladium and nickel catalysts to give saturated hydrocarbons. Industrial application : Used in the hydrogenation of vegetables oils, which contain long chains of unsaturated carbons.

Question. An organic compound A having the molecular formula \( \text{C}_3\text{H}_8\text{O} \) is a liquid at room temperature. The organic liquid A reacts with sodium metal to evolve a gas which burns causing a little explosion. When the organic liquid A is heated with concentrated sulphuric acid at 170°C, it forms a compound B which decolourises bromine water. The compound B adds on one molecule of hydrogen in the presence of Ni as catalyst to form compound C which gives substitution reactions with chlorine.
(a) What is compound A ?
(b) What is compound B ?
(c) What type of reaction occurs when A is converted into B ?
(d) What is compound C ?
(e) What type of reaction takes place when B is converted into C ?
Answer: (a) A is propanol, \( \text{CH}_3\text{–CH}_2\text{–CH}_2\text{OH} \). (b) B is propene, \( \text{CH}_3\text{CH = CH}_2 \). (c) Dehydration reaction. (d) C is propane, \( \text{CH}_3\text{CH}_2\text{–CH}_3 \). (e) Addition reaction.

Question. Give reasons :
(a) Why is pure ethanoic acid known as glacial acetic acid ?
(b) Why is ethanol used as antifreeze ?
(c) What is gasol ?
Answer: (a) Pure ethanoic acid has a low freezing point. It freezes and looks like glaciers.
(b) Ethanol mixed with water freezes at temperatures lower than water. Thus, it is used in radiators of cars in cold countries.
(c) Gasol is a mixture of petrol and alcohol.

Question. Differentiate between Diamond and Graphite.
Answer: 1. Diamond has 3-dimensional network structure; Graphite has hexagonal sheet layer structure. 2. Each carbon in diamond is bonded to four other carbon atoms; Graphite is soft and slippery. 3. No free electron is left in diamond; Each carbon in graphite has one free electron with it. 4. Diamond is a bad conductor of electricity; Graphite is a good conductor of electricity.

Question. What happens when hydrogen is added to a vegetable oil in the presence of nickel ? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in this reaction. Write the role of nickel in this reaction.
Answer: When hydrogen is added to a vegetable oil in the presence of nickel the vegetable oil is converted into saturated fat. The reaction is called hydrogenation reaction. Vegetable oil is liquid whereas saturated fat is solid at room temperature. Nickel acts as the catalyst in this reaction.

Question. What are covalent compounds ? How are they different from ionic compounds ? List any two properties of covalent compounds.
Answer: The compounds that are formed due to sharing of electrons between two atoms of compounds are having covalent bonds. Ionic compounds are formed due to transfer of electrons. Properties: (a) Covalent compounds are poor conductors of electricity. (b) They have low melting and boiling point.

Question. Ethanoic acid reacts with absolute ethanol in the presence of Conc. \( \text{H}_2\text{SO}_4 \) to form a compound.
(a) Write the smell and class of compounds to which this compound belong.
(b) Write the chemical equation for the reaction and state the role of Conc. \( \text{H}_2\text{SO}_4 \) in the reaction.
(c) Write one use of the product of this reaction.
Answer: (a) Pleasant or fruity smell and it belongs to Esters.
(b) \( \text{CH}_3\text{COOH + C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc.H}_2\text{SO}_4, \text{-H}_2\text{O}} \text{CH}_3\text{COOC}_2\text{H}_5 \). Conc. \( \text{H}_2\text{SO}_4 \) acts as a catalyst or dehydrating agent.
(c) Used in perfume industry and as flavouring agent.

Question. What is a homologous series of carbon compounds ? Write the formula of the fourth and fifth member of a homologous series having general formula \( \text{C}_n\text{H}_{2n + 1}\text{OH} \). List two differences in physical properties found in the two consecutive members of a homologous series.
Answer: A group of organic compounds having the same functional group and similar structures in which two successive members differ by –\( \text{CH}_2 \) group. \( \text{C}_4\text{H}_9\text{OH} \) and \( \text{C}_5\text{H}_{11}\text{OH} \).
(a) They differ by a mass of 14 u and show gradation in properties.
(b) Their boiling point increases with increase in molecular mass.

Question. Complete the following chemical equations :
(a) \( \text{CH}_3\text{COOH + Na}_2\text{CO}_3 \rightarrow \)
(b) \( \text{CH}_3\text{COOH + NaOH} \rightarrow \)
(c) \( \text{CH}_3\text{COOC}_2\text{H}_5 \text{ + NaOH} \rightarrow \)
Answer: (a) \( \text{CH}_3\text{COOH + Na}_2\text{CO}_3 \rightarrow 2\text{CH}_3\text{COONa + H}_2\text{O + CO}_2 \)
(b) \( \text{CH}_3\text{COOH + NaOH} \rightarrow \text{CH}_3\text{COONa + H}_2\text{O} \)
(c) \( \text{CH}_3\text{COOC}_2\text{H}_5 \text{ + NaOH} \rightarrow \text{CH}_3\text{COONa + C}_2\text{H}_5\text{OH} \)

Question. Give reason why carbon can neither form \( \text{C}^{4+} \) cations nor \( \text{C}^{4–} \) anions, but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points ?
Answer: Carbon cannot form \( \text{C}^{4+} \) cation because removal of 4 electrons from a carbon atom would require a large amount of energy. While it cannot form \( \text{C}^{4–} \) anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons. Covalent compounds do not form ions, charged particles and therefore do not conduct electricity. The intermolecular forces of attraction are weak, hence they have low melting and boiling points.

Question. Name two oxidising agents that are used for the conversion of alcohols to acids. Distinguish between ethanol and ethanoic acid on the basis of (a) litmus test, and (b) reaction with sodium hydrogen carbonate.
Answer: Alkaline \( \text{KMnO}_4 \) and Acidified \( \text{K}_2\text{Cr}_2\text{O}_7 \).
(a) Ethanol does not affect litmus paper whereas Ethanoic acid turns blue litmus red.
(b) Ethanol does not react with \( \text{NaHCO}_3 \) whereas Ethanoic acid gives brisk effervescence with the evolution of colourless \( \text{CO}_2 \) gas.

Question. Write the molecular formula of benzene and draw its structure. List in tabular form the two properties in which covalent compounds differ from ionic compounds.
Answer: \( \text{C}_6\text{H}_6 \) is the molecular formula of benzene. Properties: Covalent compounds do not conduct electricity and have low melting points; Ionic compounds conduct electricity and have high melting points.

Question. An organic compound ‘P’ is a constituent of wine. ‘P’ on reacting with acidified \( \text{K}_2\text{Cr}_2\text{O}_7 \) forms another compound ‘Q’. When a piece of sodium is added to ‘Q’ a gas ‘R’ evolves which burns with a pop sound. Identify P, Q and R and write the chemical equations of the reactions involved.
Answer: P — Ethanol, Q — Ethanoic acid, R — Hydrogen.
\( \text{CH}_3\text{CH}_2\text{OH} \xrightarrow{\text{Acidified } \text{K}_2\text{Cr}_2\text{O}_7} \text{CH}_3\text{COOH} \)
\( 2\text{CH}_3\text{COOH + 2Na} \rightarrow 2\text{CH}_3\text{COONa + H}_2 \)

Question. A student is studying the properties of acetic acid in his school laboratory. List two physical and two chemical properties which he must observe and note in his record book.
Answer: Physical properties : (a) Smell like vinegar, (b) Colourless liquid. Chemical properties : (a) turns blue litmus red, (b) gives brisk effervescence with sodium carbonate.

Question. (a) Define the term functional group. Identify the functional group present in : (i) \( \text{H—C=O(H)} \) (ii) \( \text{H—C—C=O(OH)} \)
(b) What happens when 5% alkaline \( \text{KMnO}_4 \) solution is added drop by drop to warm ethanol taken in a test tube ? State the role of alkaline \( \text{KMnO}_4 \) solution in this reaction.
Answer: (a) Functional group is the hetero atom or group of atoms attached to the carbon chain, which gives specific properties to the compound. (i) Aldehyde group (ii) Carboxylic acid.
(b) Acetic acid or Ethanoic acid is formed. Alkaline \( \text{KMnO}_4 \) solution act as an oxidizing agent.

Long Answers Type Questions

Question. (a) Compare soaps and detergents on the basis of their composition and cleansing action in hard water.
(b) What happens when ethanol is treated with sodium metal ? State the behaviour of ethanol in this reaction.
(c) Draw the structure of cyclohexane.
(d) Name the following compound \( \text{H—C—C—H} \) with \( \text{=O} \) and \( \text{—H} \) attachments.
Answer: (a) Soaps are sodium salts of carboxylic acid with long aliphatic chains. They are not effective in hard water. Detergents are sodium salts of long alkyl chains ending with a sulphonated group. They are effective in hard water.
(b) Sodium ethoxide is obtained with the liberation of hydrogen gas. \( 2\text{CH}_3\text{CH}_2\text{OH + 2Na} \rightarrow 2\text{CH}_3\text{CH}_2\text{ONa + H}_2 \). Ethanol acts as an oxidising agent.
(c) Cyclohexane is a hexagonal ring of six carbon atoms, each bonded to two hydrogens.
(d) Acetaldehyde or Ethanal.

Question. Write the chemical formula and name of the compound which is the active ingredient of all alcoholic drinks. List its two uses. Write chemical equation and name of the product formed when this compound reacts with– (a) sodium metal (b) hot concentrated sulphuric acid
Answer: Name is ethanol, formula is \( \text{C}_2\text{H}_5\text{OH} \). Uses: (i) Solvent in industries, (ii) Antiseptic solution.
(a) \( \text{C}_2\text{H}_5\text{OH + Na} \rightarrow \text{C}_2\text{H}_5\text{ONa + H}_2 \) (Sodium ethanoate).
(b) \( \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{CH}_2 = \text{CH}_2 + \text{H}_2\text{O} \) (Ethene).

Question. (a) State the reason why carbon can neither form \( \text{C}^{4+} \) cations nor \( \text{C}^{4–} \) anions, but forms covalent bonds. Also state reasons to explain why covalent compounds (i) are bad conductors of electricity. (ii) have low melting and boiling points. Write the structural formula of benzene, \( \text{C}_6\text{H}_6 \).
Answer: Carbon has a tetravalency but can't gain or lose electrons because: 1) If it gains 4 electrons, it will have \( \text{C}^{4-} \) negative charge. It is very difficult for 6 protons to hold on to 10 electrons and it becomes unstable. 2) If it loses 4 electrons, it requires a lot of energy to lose them which it can't afford and again becomes unstable. (i) Covalent bonds are formed by sharing of electrons, so no ions are formed. Thus they are bad conductors. (ii) The intermolecular forces of attraction are weak making them have low melting and boiling points. Benzene is a hexagonal ring of six carbons with alternating double bonds.