CBSE Class 10 Chemistry Carbon and Its Compounds Worksheet Set B

Short Answer :

Question. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Answer: Carbon form large number of compounds due to the following properties:
(a) Catenation → Carbon shows the property of catenation that is the ability to form bonds with other carbon atoms forming long chains both branched and unbranched chains, and even rings.
Carbon and its Compounds 15
(b) Tetravalency → Carbon has valency 4, it is capable of bonding with 4 other carbon atoms or atoms of other non-covalent elements, giving rise to compounds with specific properties depending on the elements present in the compound.
(c) Isomerism → Carbon compounds show the property of isomerism that is compounds having same molecular formula but different structural formula.

Question. What is the reactive site in the given hydrocarbon? Write its name.
H₃C—CH₂—CH==CH—CH₃
Answer: The reactive site is at a place where double bond is present.
Name of the compound is 2-pentene.

Question. Name the functional groups of the following:

Answer: (a) Chloro (Halogen) (b) Carboxylic acid (c) Ketone (d) Alcohol

Question. What is the difference in the number of carbon and hydrogen atoms between two
successive members of a homologous series? Also give the difference in their atomic masses.
Answer: The difference is of 1 carbon and two hydrogen atoms i.e., —CH₂ and mass difference is 14 a.m.u.

Question. Name the peculiar/specific chemical property exclusive in case of saturated hydrocarbons and unsaturated hydrocarbons.
Answer: Saturated hydrocarbons show substitution reaction in which hydrogen atom gets substituted by other elements or atoms. Unsaturated hydrocarbons show addition reaction, in which hydrogen atom gets added across the double bond or triple bond of the compound.

Question. Why acetic acid is called glacial acetic acid?
Answer: Acetic acid has very low melting point i.e. 290 K, hence it freezes during winters in cold countries. So it is called glacial acetic acid.

Question. Diamond and graphite show different physical properties although they are made up of carbon and shows same chemical properties. What is this property called?
Answer: This property is allotropy.
The physical properties are different because the carbon-carbon bonding in both the cases varies. In diamond one carbon atom is bonded with four other carbon atoms with strong covalent bond so it is hard, while in case of graphite each carbon forms two strong bonds with other two carbon atoms and one weak bond is formed with third carbon atom and forms hexagonal rings which slide over each other, so it is soft.

Question. Write the structural formula for bromopentane and ethanoic acid.
Answer: Bromopentane (C₅H₁₂Br) Ethanoic acid (CH₃COOH)

Question. What is esterification and give its uses?
Answer: It is the reaction in which esters are formed by reacting carboxylic acid with alcohol in the presence of concentrated sulphuric acid.
Carboxylic acid + alcohol ⎯⎯→ Ester + water
C₂H₅OH    +   CH₃COOH   ⎯⎯→   CH₃COOC₂H₅ + H₂O
Ethanol       Ethanoic acid                 Ester
Uses: (i) It is used as flavour in ice-cream and sweets.
(ii) It is a sweet smelling substance.

Question. How does ethanoic acid react with carbonates and hydrogen carbonates? Show it with the equation.
Answer: Ethanoic acid reacts with carbonates and hydrocarbonates to form salt, CO2 and H2O.
The salt formed is sodium acetate.
2CH₃COOH + Na₂CO₃ ⎯→ 2CH₃COONa + H₂O + CO₂
CH₃COOH + NaHCO₃ ⎯→ CH₃COONa + H₂O + CO₂

Question. Draw the structures of two isomers of butane.
Answer: Butane C₄H₁₀

Question. Why does carbon forms large number of compounds?
Answer: Carbon forms large number of compounds because of tetravalency and catenation property.
Tetravalency – Carbon has valency 4, to attain noble gas configuration carbon share its valence electrons with other elements like hydrogen, chlorine, etc.
Catenation – Carbon also shows the property of self-linking in which it forms long, branched or cyclic chains to form large number of compounds.

Question. A student burns a hydrocarbon in air and obtains sooty flame. Give two reasons for this observation.
Answer: Sooty flame could be obtained due to
(i) Incomplete combustion of saturated hydrocarbons.
(ii) Combustion of unsaturated hydrocarbon.

Question. Write the general formula for each of the following hydrocarbons and give one example for each.
(i) Alkene (ii) Alkyne
Answer:(i) Alkene CnH₂n e.g., C₂H₄ ethene
(ii) Alkyne CnH₂n–2 e.g., C₂H₂ ethyne

Question. Explain substitution reaction with example.
Answer: The reaction of saturated hydrocarbon with chlorine in which each hydrogen atom slowly gets substituted with chlorine atom is called substitution reaction.
CH₄ + Cl₂           ⎯⎯→       CH₃Cl + HCl
Methane Chlorine       Methyl Hydrochloric
                                     chloride acid

Question. What is denatured alcohol?
Answer: When ethanol is mixed with methanol or some poisonous substances such as copper sulphate, pyridine which makes it unfit for drinking such alcohol is called denatured alcohol.

Question. Differentiate between saturated and unsaturated hydrocarbons. Give one example for each
Answer:

Question. Draw the structures for the following compounds.
(i) Ethanoic acid
(ii) Bromopentane
(iii) Butanone
(iv) Hexanal
Are structural isomers possible for bromopentane?
Answer:

Question. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer:  Conversion of ethanol to ethanoic acid is an oxidation reaction because oxygen is added to ethanol to convert it to ethanoic acid.

In the above reaction alk. KMnO₄/acidified K₂Cr₂O₇ add oxygen to ethanol hence they are called oxidising agent.

Question. How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer: (a) Acid test: Reaction with carbonates/hydrogen carbonates.
Take samples of alcohol and carboxylic acid in 2 test tubes, and add sodium carbonate or sodium bicarbonate solution to each. The compound which will produce brisk effervescence of CO2 gas will be acid.
(b) Alcohol test: Take small amount of ethanol and ethanoic acid in test tube A and B. Add 5% solution of alkaline potassium permanganate drop by drop to this solution and warm the test tube.
The colour of potassium permanganate will disappear in test tube containing alcohol.

Question. Would you be able to check if water is hard by using detergent?
Answer:  No, because detergent forms lather in both, hard and soft water.

Question. Why are carbon and its compounds used as fuels for most applications?
Answer: Carbon and its compounds undergo combustion to produce heat, the amount of heat released can be handled and used so they are used as fuels for most applications.

Question. What change will you observe if you test soap with litmus paper (red and blue)?
Answer: Soap is alkaline in nature, hence it will turn red litmus into blue, blue litmus will remain blue.

Question. Which of the following hydrocarbons undergo addition reactions?
C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄.
Answer: Addition reaction takes place in unsaturated hydrocarbons.
Hence C₃H₆ and C₂H₂ are unsaturated hydrocarbons and will show addition reaction.

Question. Explain the mechanism of cleaning action of soaps.
Answer: Soap molecule has two ends, the charged end that gets attracted towards water is called hydrophilic and the long carbon chain that repels water is called hydrophobic end. When soap is dissolved in water, the carbon chain i.e., hydrophobic end gets attracted towards the oil, dirt and grease. The hydrophilic end stays away from this.
The micelle formation takes place.
The tail entangles dirt, oil or grease, if required the agitation is done. Lot of rinsing is a done with water so that water molecules attract charged (Na⁺) end and carries the soap molecules with dirt attached to it and clean the clothes, utensils, etc.