Chapter 9 – Carbon compounds
1. Match the pairs
| Group ‘A’ | Group ‘B’ |
|---|---|
a. C₂H₆ | 1. Unsaturated hydrocarbon |
b. C₂H₆ | 2. Molecular formula of an alcohol |
c. CH₄O | 3. Saturated hydrocarbon |
d. C₃H₆ | 4. Triple bond |
Ans:
| Group ‘A’ | Group ‘B’ |
|---|---|
a. C₂H₆ | 3. Saturated hydrocarbon |
b. C₂H₆ | 4. Triple bond |
c. CH₄O | 2. Molecular formula of an alcohol |
d. C₃H₆ | 1. Unsaturated hydrocarbon |
2. Draw an electron dot structure of the following molecules. (Without showing the circles)
a. Methane
Ans: Molecular formula – CH₄
b. Ethene
Ans: Molecular formula – C₂H₄
c. Methanol
Ans: Molecular formula – CH₃OH
d. Water
Ans: Molecular formula – H₂O
3. Draw all possible structural formulae of compounds from their molecular formula given below.
a. C₃H₈
Ans:
b. C₄H₁₀
Ans:
c. C₃H₄
Ans:
4. Explain the following terms with an example.
a. Structural isomerism
Ans: The phenomenon in which compounds have different structural formulae but have the same molecular formula is called structural isomerism.
For example: Structural formula of compound C₄H₁₀
b. Covalent bond
Ans: The chemical bond formed by sharing of two valence electrons between the two atoms is called covalent bond.
For example: Covalent bond is formed between oxygen and each of the hydrogen in a water molecule (H₂O). Each of the covalent bonds contains two electrons – one from a hydrogen atom and one from the oxygen atom. Both atoms share the electrons.
c. Hetero atom in a carbon compound
Ans: The atoms of the elements, substitute one or more hydrogen atoms in the hydrocarbon chain and thereby, the tetravalency of carbon is satisfied. The atom of the element which is a substitute for hydrogen is referred as hetero atom.
For example: CH₃OH. In this example, one hydrogen atom in methane CH₄ is replaced by –OH group. OH is a functional group. So, OH is a heteroatom.
d. Functional group
Ans: The hetero atom or group of hetero atoms, present in a compound due to which the compound acquires specific chemical properties irrespective of the length and nature of the carbon chain in it, are called a functional group.
For example: Alcohol group (– OH).
Any hydrocarbon that has – OH substituent. e.g. methanol (CH₃OH)
e. Alkane
Ans: Alkanes are chemical compounds that consist of carbon and hydrogen atoms, so they are also called hydrocarbons, the chemical structure of alkanes only consists of single covalent bonds. As they contain only single bonds, and because of that each carbon atom is saturated with hydrogen atoms. Alkanes are, therefore, referred to as saturated hydrocarbons.
For example: Methane CH₄, Ethane C₂H₆, Butane C₄H₁₀
f. Unsaturated hydrocarbon
Ans: Hydrocarbons in which carbon atoms are linked to each other by double or triple bonds are known as unsaturated hydrocarbons.
For example: Ethene (C₂H₆), Ethyne (C₂H₂)
g. Homopolymer
Ans: When the polymers are formed by repetition of a single monomer. These are called homopolymers.
For example: Polyvinyl Chloride (PVC) into starch, cellulose, laminarin and glucans. Synthesis of polyethylene is as follows:
h. Monomer
Ans: A macromolecule formed by regular repetition of a small unit is called polymer. The small unit that repeats regularly to form a polymer is called monomer.
For example: Vinyl chloride polymerizes into polyvinyl chloride of PVC. Glucose polymerises the same functional group in the place of a particular hydrogen atom in the chains having sequentially increasing length is called Homologous Series.
i. Reduction
Ans: Reduction is the type of reaction in which loss of oxygen and gain of hydrogen occurs or in terms of electron transfer, we can define reduction reactions as the type of reactions where gain of electrons takes place.
For example: CH₃–CHO → CH₃– CH₂–OH
In this example we get to see reduction of CH₃–CHO by gain of hydrogen.
j. Oxidant
Ans: Substances that can give oxygen to other substances are called oxidants or oxidizing agents.
For example: Potassium permanganate or potassium dichromate are commonly used as oxidizing agents.
5. Write the IUPAC names of the following structural formulae.
a. CH₃–CH₂–CH₂–CH₃
Ans: Butane
b. CH₃–CH(OH)–CH₃
Ans: Propan-2-ol
c. CH₃–CH₂–COOH
Ans: Propanoic acid
d. CH₃–CH₂–NH₂
Ans: Ethan-1-amine
e. CH₃–CHO
Ans: Ethanal
f. CH₃–CO–CH₂–CH₃
Ans: Butanone
6. Identify the type of the following reaction of carbon compounds.
a. CH₃–CH₂–CH₂–OH → CH₃–CH₂–COOH
Ans: Oxidation reaction (acidic KMnO₄).
b. CH₃–CH₂–CH₃ → 3 CO₂ + 4 H₂O
Ans: Combustion reaction
c. CH₃–CH=CH–CH₃ + Br₂ → CH₃–CHBr–CHBr –CH₃
Ans: Addition reaction
d. CH₃–CH₃ + Cl₂ → CH₃–CH₂–Cl + HCl
Ans: Substitution reaction
e. CH₃–CH₂–CH₂–CH₂–OH → CH₃–CH₂–CH=CH₂ + H₂O
Ans: Dehydration reaction.
f. CH₃–CH₂–COOH + NaOH → CH₃–CH₂–COO–Na⁺ + H₂O
Ans: Neutralization reaction(reaction with base).
g. CH₃–COOH + CH₃–OH → CH₃–COO–CH₃+ H₂O
Ans: Esterification reaction
7. Write structural formulae for the following IUPAC names.
a. pent -2- one
Ans: Molecular formula – C₅H₁₀O
b. 2- chlorobutane
Ans: Molecular formula – C₄H₉Cl
c. propan -2- ol
Ans: Molecular formula – C₃H₇OH
d. methanal
Ans: Molecular formula – CH₃OH
e. butanoic acid
Ans: Molecular formula – CH₃CH₂CH₂COOH
f. 1- bromopropane
Ans: Molecular formula – C₃H₇BR
g. ethanamine
Ans: Molecular formula – C₂H₅NH₂
h. butanone
Ans: Molecular formula – C₄H₈O
8. Write answers as directed.
a. What causes the existence of a very large number of carbon compounds ?
Ans:
(i) Carbon is the only element that can form so many different compounds because each carbon atom can form four chemical bonds with other atoms.
(ii) Having the atomic number 6, every carbon atom has a total of six electrons. The carbon atom’s four valence electrons can be shared by other atoms, forming covalent bonds, giving them the ability to form long carbon – to – carbon chains; they can even join “head – to – tail” to make rings of carbon atoms.
(iii) Carbon atoms can share not only a single electron with another atom to form a single bond, but it can also share two or three electrons, forming double or triple bonds.
(iv) This makes a huge number of different possible molecules. Hence, carbon forms a large number of compounds, because of all these properties.
b. Saturated hydrocarbons are classified into three types. Write these names giving one example each.
Ans: Saturated hydrocarbons in which the carbon atoms are linked to each other only by single bonds (C – C) are known as saturated hydrocarbons.
They are classified into:
c. Give any four functional groups containing oxygen as the heteroatom in it. Write name and structural formula of one example each.
Ans:
d. Give names of three functional groups containing three different hetero atoms. Write name and structural formula of one example each.
Ans:
e. Give names of three natural polymers. Write the place of their occurrence and names of monomers from which they are formed.
Ans: A macromolecule formed at regular repetition of a small unit is called polymer. The small unit that repeats itself regularly to form a polymer is called monomer. Most of the structure of living things are composed of natural polymers.
f. What is meant by vinegar and gashol? What are their uses ?
Ans:
(i) Vinegar: Ethanoic acid is most commonly known as acetic acid. Its dilute solution in water (5-8 %) is known as vinegar.
(ii) Uses: Vinegar is used as a cooking ingredient, as a preservative in pickles, food storage, vinegar is also used for fermentation and also in medicinal fields.
(iii) Gashol: Ethanol is a clean fuel. Therefore, it is used as an additive to increase the efficiency of petrol. Such a fuel is called gashol.
(iv) Uses: It is used as a fuel.
g. What is a catalyst ? Write any one reaction which is brought about by use of catalyst ?
Ans: Catalyst: A substance which increases the rate of reaction without causing any disturbance is called a catalyst. Vegetable oils are converted into vanaspati ghee by passing hydrogen in the presence of nickel as a catalyst.
