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Hydrocarbon and its CompoundsSolved Questions· Unit 18
Science & Technology · Chapter 18
34 solved questions

Chapter 18: Hydrocarbon and its Compounds

Every question in this chapter, answered and explained — step-by-step solutions drawn live from the chapter library across 8 question sections.

Very Short Answer Questions10Short Answer Questions7Give Reason Questions5Differentiate Between3Long Answer Questions2Diagram-Based Questions2Application / Conceptual Questions2Additional SEE Practice3
01

Very Short Answer Questions

10
1SEE Boardqb-q0

What is a hydrocarbon?

Ans.A hydrocarbon is an organic compound composed only of carbon and hydrogen atoms. Example: methane (CH4), ethane (C2H6).
2SEE Boardqb-q1

What is a saturated hydrocarbon?

Ans.A hydrocarbon having only a single covalent bond between carbon atoms is called a saturated hydrocarbon. It is also called an alkane.
3SEE Boardqb-q2

What is an unsaturated hydrocarbon?

Ans.A hydrocarbon having a double or triple covalent bond between carbon atoms is called an unsaturated hydrocarbon.
4SEE Boardqb-q3

What is an alkyl radical?

Ans.The group of atoms formed by removing one hydrogen atom from an alkane molecule is called an alkyl radical. General formula: CnH2n+1.
5SEE Boardqb-q4

What is a functional group?

Ans.An atom or group of atoms that determines the structure and chemical reactivity of a group of organic compounds is called a functional group, e.g. -OH, -COOH.
6SEE Boardqb-q5

What is a homologous series?

Ans.A series of compounds represented by the same general formula, where adjacent members differ by a -CH2- group, is called a homologous series.
7SEE Boardqb-q6

What is the general formula of alkane, alkene, and alkyne?

Ans.Alkane = CnH2n+2, Alkene = CnH2n, Alkyne = CnH2n-2.
8SEE Boardqb-q7

What is the IUPAC name of glycerol?

Ans.The IUPAC name of glycerol is propane-1,2,3-triol.
9SEE Boardqb-q8

What is the functional group of alcohol?

Ans.The functional group of alcohol is hydroxyl (-OH).
10SEE Boardqb-q9

Which gas is known as marsh gas?

Ans.Methane (CH4) is known as marsh gas.
02

Short Answer Questions

7
1SEE Boardqb-q10

What are hydrocarbons? Write any four examples.

Ans.Hydrocarbons are organic compounds made of only carbon and hydrogen atoms. Examples: methane (CH4), ethane (C2H6), ethene (C2H4), ethyne (C2H2).
2SEE Boardqb-q11

What do you mean by a saturated hydrocarbon? Write with examples.

Ans.A saturated hydrocarbon has only single covalent bonds between carbon atoms, general formula CnH2n+2. It is stable and less reactive. Examples: methane (CH4), ethane (C2H6), propane (C3H8).
3SEE Boardqb-q12

Introduce methane gas along with its two uses.

Ans.Methane is a colourless, odourless hydrocarbon found in marshy places and biogas, with molecular formula CH4. Uses: (1) used as fuel for cooking (biogas), (2) used to prepare carbon black for printing ink and shoe polish.
4SEE Boardqb-q13

What is alcohol? Write its types on the basis of the hydroxyl group.

Ans.Alcohol is a compound formed by replacing one or more hydrogen atoms of an alkane with an -OH group. Types: monohydric (1 -OH, e.g. methanol CH3OH), dihydric (2 -OH, e.g. glycol CH2OHCH2OH), and trihydric (3 -OH, e.g. glycerol C3H5(OH)3).
5SEE Boardqb-q14

Write the molecular formula, condensed formula, and structural formula of ethylene, propene, acetylene, ethyl alcohol, and glycerol.

Ans.Ethylene (ethene) C2H4, condensed H2C=CH2. Propene C3H6, condensed H3C-CH=CH2. Acetylene (ethyne) C2H2, condensed HC≡CH. Ethyl alcohol C2H5OH, condensed H3C-CH2-OH. Glycerol C3H5(OH)3, structural formula shows three carbons each bonded to one -OH group.
6SEE Boardqb-q15

Write any three uses of methane gas.

Ans.
  1. (1) Used as fuel for cooking as biogas/gobar gas,
  2. (2) used to prepare carbon black,
  3. (3) used in industrial preparation of hydrogen gas.
7SEE Boardqb-q16

Write major uses of ethane and propane.

Ans.Ethane is used in metal welding and to prepare compounds like ethyl chloride. Propane is used as a fuel because it is highly flammable, and as a coolant in petroleum industries.
03

Give Reason Questions

5
1SEE Boardqb-q17

Ethane is known as a saturated hydrocarbon. Why?

Ans.Ethane has only a single covalent bond between its two carbon atoms, with the general formula CnH2n+2. Since all carbon valencies are fully satisfied with single bonds, it is called a saturated hydrocarbon.
2SEE Boardqb-q18

Glycerol is called a trihydric alcohol. Why?

Ans.Glycerol is formed by replacing three hydrogen atoms of propane with three hydroxyl (-OH) groups, one on each carbon atom. Because it contains three -OH groups, it is called a trihydric alcohol.
3SEE Boardqb-q19

Why is the bond between carbon atoms of ethylene (ethene) weak?

Ans.Ethylene has a double covalent bond (C=C) between its carbon atoms. A double bond is less stable than a single bond because it is more strained and reactive, which makes it easier to break, so unsaturated compounds are more reactive.
4SEE Boardqb-q20

Why are alkanes also called paraffins?

Ans.Alkanes have only single covalent bonds, which makes them very stable and less reactive towards most chemical reagents. Because of this low reactivity, they are also called paraffins.
5SEE Boardqb-q21

Why is methane called marsh gas?

Ans.Methane is produced by the decomposition of plant and animal matter under water in marshy and swampy areas, and it rises above the water there. Because it is commonly found in marshes, it is called marsh gas.
04

Differentiate Between

3
1SEE Boardqb-q22

Differentiate between saturated and unsaturated hydrocarbon.

Saturated HydrocarbonUnsaturated Hydrocarbon
Has a single covalent bond between carbon atoms.Has a double or triple covalent bond between carbon atoms.
Stable and less reactive (also called paraffin).Unstable and highly reactive (also called olefin).
General formula CnH2n+2 (alkane).General formula CnH2n (alkene) or CnH2n-2 (alkyne).
2SEE Boardqb-q23

Differentiate between alkane and alkene.

AlkaneAlkene
Carbon atoms are joined by a single covalent bond.Carbon atoms are joined by a double covalent bond.
General formula CnH2n+2.General formula CnH2n.
Example: methane, ethane, propane.Example: ethene, propene, butene.
3SEE Boardqb-q24

Differentiate between monohydric alcohol and dihydric alcohol.

Monohydric AlcoholDihydric Alcohol
Contains only one hydroxyl (-OH) group.Contains two hydroxyl (-OH) groups.
Example: methanol (CH3OH), ethanol (C2H5OH).Example: glycol (CH2OHCH2OH).
05

Long Answer Questions

2
1SEE Boardqb-q25

What is alcohol? Explain its types with examples, molecular formula, and structural formula.

Ans.Alcohols are organic compounds formed by replacing one or more hydrogen atoms of an alkane with a hydroxyl (-OH) group; -OH is their functional group, and the general formula is CnH2n+1OH.
2SEE Boardqb-q26

Describe saturated and unsaturated hydrocarbons with their general formulas, examples, and differences.

Ans.Saturated hydrocarbons (alkanes) have only single covalent bonds between carbon atoms (CnH2n+2), are stable, and are also called paraffins; examples are methane, ethane, and propane. Unsaturated hydrocarbons have a double bond (alkenes, CnH2n) or triple bond (alkynes, CnH2n-2) between carbon atoms, are less stable and more reactive, and are also called olefins; examples are ethene and ethyne.
06

Diagram-Based Questions

2
1SEE Boardqb-q27

Draw and label the ball-and-stick models of methane, ethane, and propane.

Ans.Draw one central carbon atom bonded to four hydrogen atoms for methane (CH4); two carbon atoms joined by a single bond, each further bonded to hydrogens, for ethane (C2H6); and three carbon atoms in a chain, each bonded to hydrogens, for propane (C3H8). Label carbon atoms and hydrogen atoms clearly.
2SEE Boardqb-q28

Study the structural formula given (H3C-CH3 type, two carbons each bonded to three hydrogens and to each other) and answer: (i) name the compound (ii) is it saturated? Give reason (iii) which compound forms if one hydrogen is replaced with -OH?

Ans.
  1. (i) The compound is ethane (C2H6).
  2. (ii) Yes, it is a saturated hydrocarbon because the two carbon atoms are joined by a single covalent bond only.
  3. (iii) If one hydrogen atom is replaced by -OH, the compound formed is ethanol (ethyl alcohol, C2H5OH).
07

Application / Conceptual Questions

2
1SEE Boardqb-q29

Rama has a problem of dry skin on her hands, feet, and face. Which compound can be used to solve her problem? Write its IUPAC name and structural formula.

Ans.Glycerol can be used, as it traps moisture and prevents dryness of the skin. Its IUPAC name is propane-1,2,3-triol, and its structural formula shows a 3-carbon chain with a hydroxyl (-OH) group attached to each carbon.
2SEE Boardqb-q30

Name the alcohol used for each of the following purposes: (i) to make formaldehyde (ii) used in thermometers (iii) used as an antiseptic (iv) to prepare alcoholic beverages.

Ans.
  1. (i) Methanol (methyl alcohol),
  2. (ii) Ethanol (ethyl alcohol),
  3. (iii) Ethanol (ethyl alcohol),
  4. (iv) Ethanol (ethyl alcohol).
08

Additional SEE Practice

3
1SEE Boardqb-q31

Why is glycerol soluble in water and alcohol but insoluble in ether?

Ans.Glycerol contains three -OH (hydroxyl) groups that form hydrogen bonds with water and alcohol molecules, making it soluble in them; ether cannot form such hydrogen bonds with glycerol, so glycerol is insoluble in ether.
2SEE Boardqb-q32

Which hydrocarbon is included in the alkane group: methane, ethene, acetylene, or propyne?

Ans.Methane is included in the alkane group, as it has only single covalent bonds (CH4, CnH2n+2).
3SEE Boardqb-q33

What happens to unsaturated fatty acids during hydrogenation of vegetable oil?

Ans.During hydrogenation, hydrogen is added across the double bonds of unsaturated fatty acids, converting them into saturated fatty acids, as in the preparation of Vanaspati ghee.
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