CBSE Class 10 Chemistry Carbon and Its Compounds Worksheet Set C

Question. Ethane, with the molecular formula C₂H₆ has :
(A) 6 covalent bonds
(B) 7 covalent bonds
(C) 8 covalent bonds
(D) 9 covalent bonds 

Answer : B

Question. A molecule of ammonia (NH₃) has :
(A) only single bonds
(B) only double bonds
(C) only triple bonds
(D) two double bonds and one single bond 

Answer : A

Question. Which of the following is not observed in a homologous series? 
(A) Change in chemical properties
(B) Difference in —CH₂ and 14u molecular mass
(C) Gradation in physical properties
(D) Same functional group 

Answer : A

Question. The correct electron dot structure of a water molecule is :

Answer : C

Question. Which of the following does not belong to the same homologous series?
(A) CH₄
(B) C₂H₆
(C) C₃H₈
(D) C₄H₈ 

Answer : D

Question. Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms, e.g. hydrogen. After the formation of four bonds, carbon attains the electronic configuration of
(A) helium
(B) neon
(C) argon
(D) krypton 

Answer : B

Question. Which of the following statements are usually correct for carbon compounds?
(i) These are good conductors of electricity.
(ii) These are poor conductors of electricity.
(iii) These have strong forces of attraction between their molecules.
(iv) These do not have strong forces of attraction between their molecules.
(A) (i) and (iii)
(B) (ii) and (iii)
(C) (i) and (iv)
(D) (ii) and (iv) 

Answer : D

Assertion and Reason Based MCQs :

Directions : In the following questions, A statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as:
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false.
(D) A is false and R is true.

Question. Assertion (A): Most of the carbon compounds are good conductors of electricity.
Reason (R): They do not dissociate to form ions and remain as molecules.

Answer : D

Question. Assertion (A): Following are the members of a homologous series : CH₃OH, CH₃CH₂OH, CH₃CH₂CH₂OH
Reason (R): A series of compounds with same functional group but differing by – CH₂ – unit is called a homologous series.

Answer : A

Question. Assertion (A): Carbon atoms have the ability to form four strong covalent bonds.
Reason (R): Carbon has the ability to make single, double and triple bonds with itself.

Answer : B

Question. Assertion (A): Following are the structural isomers of butane.
Reason (R): Structural isomers have the same molecular formula but they differ in their structures.

Answer : A

Question. Assertion (A): In a homologous series of alcohols, the formula for the second member is C₂H₅OH and the third member is C₃H₇OH.
Reason (R): The difference between the molecular masses of the two consecutive members of a homologous series is 144.

Answer : C

Question. Assertion (A): Third member of alkane is propane (C₃H₈)
Reason (R): It is obtained from general formula C_nH_2n + 2

Answer : A

Case-based MCQs :

Read the passage and answer the given questions.

A homologous series is a series of organic compounds which belong to the same family (i.e. possess same functional group) and show similar chemical properties. The members of this series are called homologous and differ from each other by the number of CH₂ units in the main carbon chain.

Question. The chemical properties of which of the following compounds is similar to the butane ? 
(A) Butyne
(B) Propene
(C) Propyne
(D) Pentane

Answer : D

Question. Which of the following is not the property of a homologous series ? 
(A) They show similar chemical properties.
(B) They differ by 14 units by mass.
(C) They all contain double bond
(D) They can be represented by a general formula.

Answer : C

Question. Which of the following represent the name and formula of the 2^nd member of homologous series having general formula C_nH_2n + 2 ? 
(A) Methane CH₄
(B) Ethane C₂H₆
(C) Ethene C_2H4
(D) Ethyne C₂H₆

Answer : B

Question. The difference between two consecutive members in a homologous series in alkanes in terms of molecular mass and number of atoms of elements is: 
(A) 14 a.m.u and CH₂ respectively
(B) 12 a.m.u and CH₃ respectively
(C) 14 a.m.u and CH respectively
(D) 12 a.m.u and CH₃ respectively

Answer : A

Read the given passage and answer the questions given below :

Carbon has the unique property to form bonds with other atoms of carbon. Fig.A

Question. Carbon forms large number of compounds due to :
(A) Catenation only
(B) Tetravalency only
(C) Both catenation and tetravalency
(D) None of the above

Answer : C

Question. Carbon is : 
(A) Divalent
(B) Monovalent
(C) Tetravalent
(D) Trivalent

Answer : C

Question. Name the characteristic property of carbon as depicted in the fig. 
(A) Catenation
(B) Polymerisation
(C) Isomerisation
(D) None of the above.

Answer : A

Question. Write the name and structure of a saturated compound in which 6 carbon atoms are arranged in a ring. 
(A) Hexane
(B) Cyclohexane
(C) Pentane
(D) Cyclopentane

Answer : B

Read the passage and answer the questions given below :

Homologous series is a series of compounds with similar chemical properties and same functional group differing from the successive member by —CH₂ unit. Carbon chains of varying length have been observed in organic compounds having the same general formula. Such organic compounds that vary from one another by a repeating unit and have the same general formula form a series of compounds. Alkanes with general formula C_nH_2n+2, alkenes with general formula CnH2n and alkynes with general formula C_nH_2n – 2 form the most basic homologous series in organic chemistry.
All the members belonging to this series have the same functional groups. They have similar physical properties and follow a fixed gradation with increasing mass. This series has enabled scientists to study different organic compounds systematically. They can predict the properties of organic compounds belonging to a particular homologous series based on the data available from the other members of the same series. The study of organic compounds has been simplified.

Question. Which of these statements is correct about the members of a homologous series ? 
(A) They have same empirical formula.
(B) They have same general formula.
(C) They have same molecular formula.
(D) They have same physical properties.

Answer : B

Question. What is the molecular formula of the 5th member of the homologous series of carbon compounds is represented by the general formula C_nH_2n+1OH ?
(A) C₅H₁₀
(B) C₅H₁₁OH
(C) C₅H₁₂OH
(D) C₅H₁₁CHO

Answer : B

Question. The general formula for alkene is : 
(A) C_nH_2n
(B) C_nH_2n+
(C) C_nH_{2n– 2}
(D) C_nH_2n+1

Answer : A

Question. Two compounds CH₃OH and C₂H₅OH are provided. The difference in its formulae and molecular masses are ___I___ and ____II____. 
(A) I- CH₃, II- 16 units
(B) I- CH₂, II- 14 units
(C) I- CH₄, II- 18 units
(D) I - CH₃, II- 16 units

Answer : B

VI. VALUE-BASED QUESTIONS

Q1. A student reports the police about the illegal vending of alcohol near his school. He also knew about denatured alcohol.
(a) What is denatured alcohol?
(b) What would happen if somebody consumes denatured alcohol?
(c) What value is reflected by a student who reported the matter to police?
Answer : (a) Denatured alcohol is ethanol when added with poisonous methanol or copper sulphate solution.
(b) On drinking denatured alcohol a person may die.
(c) Value reflected by student is society’s law and order.

Q3. Geeta helps her mother in washing clothes, toilets, balconies every Sunday. She uses the leftover detergent water of washing machine to clean toilets.
(a) Why is detergent used in washing clothes?
(b) Give one advantage of detergent over soap.
(c) What value of Geeta is reflected in the above task?
Answer : (a) Detergents have strong cleansing ability and can remove oil and dirt from clothes or other surfaces.
(b) Soap cannot be used in hard water but detergents can be used in hard water.
(c) Geeta is trying to reduce water pollution and water shortage problem. She also shows helpful to her mother and responsible behaviour.

Q2. Suman always carried her tiffin box in a jute bag while most of her friends got it packed in a poly bag.
(a) What type of bonding is present in polythene?
(b) Give one advantage of carrying jute and disadvantage of poly bag.
(c) Which value is reflected in Suman by using jute bag?
Answer : (a) In polythene, long chain of ethene is present – C = C –.
(b) Jute bag is biodegradable and will not cause pollution. While poly bag is nonbiodegradable and causes pollution.
(c) Suman shows the value of a responsible behaviour.

Question. Write the structure of an alcohol with three carbon atoms in the molecule.
Answer : 

Question. Which of the following organic compounds belong to the same homologous series:
C₂H₆, C₂H₆O, C₂H₆O₂, CH₄O
Answer : C₂H₆O (C₂H₅OH) and CH₄O (CH₃OH)

Question. How many covalent bonds are there in a molecule of ethane (C₂H₆)?
Answer : There are 7 covalent bonds.

Question. Write the electron dot diagram of ethane (C₂H₆) molecule.
Answer : 

Question. Write the number of covalent bonds in propane, C₃H₈. 
Answer : There are 10 covalent bonds

Question. State the valency of the carbon atom in (i) an alkane (ii) an alkyne.
Answer : (i) Four, (ii) Four

Question. Name a cyclic unsaturated carbon compound.
Answer : Benzene is cyclic unsaturated carbon compound.

Question. Select alkenes and alkynes from the following:
C₂H₄, C₃H₄, C₂H₂, C₄H₈
Write their structural formula also. 
Answer : C₂H₄ and C₄H₈ are alkenes, C₃H₄ and C₂H₂ are alkynes

Question. Give difference between soap and detergent.
Answer : 

Question. (a) Write the names of the functional groups in:

(b) Describe a chemical test to distinguish between ethanol and ethanoic acid.
(c) Write a chemical equation to represent what happens when hydrogen gas is passed through an unsaturated hydrocarbons in the presence of nickel as a catalyst.
Answer : (a) (i) Ketone (ii) Aldehyde
(b) On adding Na₂CO₃/NaHCO₃, the test tube containing ethanoic acid produces brisk effervescence of CO₂ gas. Alcohol will not show any reaction.
CH₃COOH + NaHCO₃ ⎯→ CH₃COONa + CO₂ + H₂O
C₂H₅OH + NaHCO₃ ⎯→ No reaction

Question. An organic compound ‘X’ which is also called antifree mixture has the molecular formula C₂H₆O ‘X’ on oxidation gives a compound ‘Y’ which gives effervescence with a baking soda solution. What can X and Y be? Write their structural formula.
Answer : X is ethanol, (C₂H₅OH)
Y is ethanoic acid (CH₃COOH)
Structural formula

Question. Write the structures of isomers of hexane.
Answer : 

Question. Give two uses of ethanol and one harmful effect of it.
Answer : Ethanol is a good solvent so it is used in making medicines such as tincture iodine, cough syrups and many tonics. Ethanol is also used in making alcoholic drinks.
Harmful effects: Intake of small amount of ethanol leads to drunkenness. Intake of even small amount of ethanol can be lethal. Long-term use or consumption can lead to severe health problems.

Q26. (a) Why are covalent compounds generally poor conductors of electricity?
(b) Name the following compound:

(c) Name the gases evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?
Answer : (a) Covalent compound do not form ions.
(b) Propanone
(c) Ethanoic acid reacts with sodium carbonate to produce carbon dioxide gas. To prove the presence of this gas allow it to pass through lime water (freshly
prepared). It turns lime water milky.
Equation
                            2CH₃COOH + 2Na₂CO₃ → 2CH₃COONa + H₂O + CO₂
Test for the gas evolved → Ca(OH)₂ + CO₂ → CaCO₃ + H₂O
                                          Lime water               Milky ppt.

Question. Write the chemical equations for the following reactions:
(i) Conversion of oils into fats (ii) Oxidation of ethanol
(iii) Ethanoic acid with sodium hydroxide.
Answer :

Question. Giving chemical equations of the reactions write what happens when
(i) Ethanol is heated with excess of concentrated sulphuric acid at 443 K.
(ii) Ethanoic acid reacts with ethanol in presence of an acid.
(iii) Ester with molecular formula CH₃COOC₂H₅ reacts with sodium hydroxide.
Answer :

Question. (a) What is a ‘homologous series’ of substances?
(b) In an organic compound, which parts largely determine its physical and chemical properties?
(c) Write a chemical equation to represent the reaction of ethanol with acidified solution of potassium dichromate.
Answer : (a) Homologous series is a series of organic compounds having same general formula, all members of the compounds show same chemical properties and slight gradation in physical properties.
(b) Functional group.

Question. (a) Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
(b) (i) Name the products formed when ethanol burns in air.
(ii) What two forms of energy are liberated on burning alcohol?
(c) Why is the reaction between methane and chlorine considered a substitution reaction?
Answer : (a) On adding bromine water, the unsaturated hydrocarbon decolourises the bromine water but the saturated hydrocarbon will not decolourise bromine water.
(b) (i) Ethanol burns in air to produce carbon dioxide and water.
C₂H₅OH + 3O₂ ⎯⎯→ 3CO₂ + 3H₂O + heat
(ii) Two forms of energy obtained are heat energy and light energy.
(c) When methane reacts with chlorine, the hydrogen atom of methane is replaced by chlorine atom step by step and hence it is termed as substitution reaction.
CH₄ + Cl₂ ⎯⎯→ CH₃Cl + HCl

Question. Differentiate between ethanol and ethanoic acid on basis of the following test:
(i) Blue litmus test (ii) Reaction with sodium bicarbonate (iii) Sodium metal test
Answer : 

Question. Give reason for the following observations:
(a) The element carbon forms a very large number of compounds.
(b) Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
(c) Use of synthetic detergents causes pollution of water.
Answer : (a) Carbon forms large number of compounds due to its property of catenation, i.e. self linking. They form isomeric compounds i.e. compounds with same molecular formula but different structural formula.
(b) The vessels blacken due to deposits of black carbon particles on it which is caused due to incomplete combustion of fuel. Air holes are adjusted so that air enters through the holes and helps in complete combustion of the fuel.
(c) Synthetic detergent is non-biodegradable, it remains in the water thereby causing water pollution.

Question. (a) Name the compound CH₃CH₂OH and identify its functional group.
(b) Give a chemical test to distinguish between ethanol and ethanoic acid.
(c) Name the product formed when an organic acid reacts with an alcohol in presence of an acid catalyst. What is the name assigned to this type of reaction?
Answer : (a) CH₃CH₂OH – Ethanol
Functional group: alcohol (–OH)
(b) Take two test tubes, add ethanol and ethanoic acid in test tube A and B respectively. Add sodium carbonate/sodium hydrogen carbonate solution in both the test tubes, the test tube which will produce brisk effervescence of CO₂ gas will contain ethanoic acid. Ethanol do not evolve CO₂ gas when reacted with Na₂CO₃ / NaHCO₃.
(c) When an organic acid reacts with an alcohol in presence of an acid as catalyst, it produces fruity smelling compound called ester. Such a reaction is called esterification.

Question. (a) What is vinegar?
(b) Describe with a chemical equation, what happens when sodium hydrogen carbonate reacts with ethanoic acid.
Answer : (a) The 5% – 10% aqueous solution of acetic acid is called vinegar.
(b) CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂
Acetic acid                                           Sodium acetate
Ethanoic acid reacts with sodium bicarbonate to produce brisk effervescence of CO2 gas and sodium acetate.

Question. (a) Name the compound CH₃COOH and identify its functional group.
(b) Give a chemical test to identify this compound.
(c) Name the gas evolved when this compound acts on solid sodium carbonate. How would you identify this gas?
Answer : (a) Ethanoic acid, functional group is—COOH (Caboxylic/group)
(b) Take few drops of ethanoic acid in a test tube and add sodium hydrogen carbonate solution to it. Brisk effervescence of CO2 gas is formed.
(c) CO₂ gas is evolved. To identify the gas, pass it through freshly prepared limewater, it turns milky due to the formation of milky white precipitate of CaCO₃.
Ca(OH)₂ + CO₂ ⎯⎯→ CaCO₃ + H₂O
                                          White ppt.