Q 1 – Which of the following statements are correct for carbon compounds?
(i) Most carbon compounds are good conductors of electricity.
(ii) Most carbon compounds are poor conductors of electricity.
(iii) Force of attraction between molecules of carbon compounds is not very strong.
(iv) Force of attraction between molecules of carbon compounds is very strong.
(a) (ii) and (iv)
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (i) and (iii)
(b) (ii) and (iii)
Q 2 – C3H8 belongs to the homologous series of
(a) Alkynes
(b) Alkenes
(c) Alkanes
(d) Cyclo alkanes
(c) Alkanes
Q 3 – The number of isomers of pentane is
(a) 2
(b) 3
(c) 4
(d) 5
(b) 3
Q 4 – Which of the following will undergo addition reactions?
(a) CH4
(b) C3H8
(C) C2H6
(d) C2H4
Q 5 – When ethanoic acid is treated with NaHCO^ the gas evolved is
(a) H2
(b) CO2
(c) CH4
(d) CO
(b) CO2
Q 6 – Ethanol on complete oxidation gives
(a) acetic acid/ethanoic acid
(b) CO2 and water
(c) ethanal
(d) acetone/ethanone
(b) CO2 and water
Q 7 – Name the functional group present in CH3COCH3.
(a) Alcohol
(b) Carboxylic acid
(c) Ketone
(d) Aldehyde
(c) Ketone
Q 8 – Addition reactions are undergone by
(a) saturated hydrocarbons (alkanes)
(b) only alkenes
(c) only alkynes
(d) both alkenes and alkynes
(d) both alkenes and alkynes
Q 9 – Identify ‘A’ in the following reaction:
CH3COOH + Na2CO3 → A + CO2 + H0O
(a) CH3COONa
(b) CH2(Na)COOH
(c) NaOH
(d) NaHCO3
(a) CH3COONa
Q 10 – Which of the following belongs to homologous series of alkynes?
C6H6, C2H6, C2H4, C3H4.
(a) C6H6
(b) C2H4
(C) C2H6
(d) C3H4
(d) C3H4
Q 11 – Which of the following is not observed in a homologous series? Give reason for your choice.
a) Change in chemical properties
b) Difference in ¯CH2 and 14u molecular mass
c) Gradation in physical properties
d) Same functional group
a) Change in chemical properties
Q 12 – 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
b. Neon
Q 13 – The first member of alkyne homologous series is _________. Also write the chemical formula of it.
a. Ethyne
b. Ethene
c. Propyne
d. Methane
a. Ethyne
Q 14 – Which of the following does not belong to the same homologous series?
a. Methane CH4
b. Ethane C2 H6
c. Propane C3 H8
d. Butane C4 H8
d. Butane C4 H8
Q 15 – State two characteristic features of carbon which give rise to large number of carbon compounds.
(i) Catenation – The property of carbon element due to which its atoms can join one another to form long carbon chains is called catenation. It means carbon atoms have the tendency to link with one another through covalent bonds to form chains and rings.
(ii) Tetravalency – Carbon has a valency of four.
Q 16 – Nowadays hydrocarbon is used for ripening of many raw fruits. Name the Hydrocarbon .
- Unsaturated hydrocarbons are mainly used for artificial ripening of fruits.
- Ethene and Ethyne containing double and triple bond respectively, are used for ripening of fruits.
Q 17 – Define allotropes of an element and name the three allotropic forms of carbon?
Allotropy is a property by which an element can exist in more than one form that is physically different and chemically similar.
Carbon exists in different allotropic forms as follows.
(i) Diamond.
(ii) Graphite.
(iii) Fullerene.
Q 18 – Differentiate between saturated and unsaturated hydrocarbons. Give one example for each.
- The hydrocarbons can be of two types, saturated and unsaturated hydrocarbons.
Saturated Hydrocarbon | Unsaturated hydrocarbons |
| The simplest hydrocarbons in which carbon-carbon atoms and carbon-hydrogen atoms are held together by single bonds are known as saturated hydrocarbon | The hydrocarbons in which Carbon-Carbon atoms and Carbon-Hydrogen atoms are held together by the double or triple bond are known as unsaturated Hydrocarbons. |
| They have Sp3 hybridized Carbon atoms and are called alkanes | The double-bonded compounds are called alkenes and the general formula for alkenes is . |
| They are having a general formula . | The triple bonded compounds are called alkynes and the general formula for alkynes is . |
| An Example of saturated hydrocarbon is Ethane and Propane | An example of unsaturated hydrocarbon is Ethene and Ethyne |
Q 19 – A piece of black electrode used in a dry cell on strong heating in the air gave a colorless gas which turned lime – water milky. What was the material of the electrode?
The black electrode that gives a colorless gas upon strong heating in air and turns lime water milky is likely to be composed of carbon. The gas that is evolved is carbon dioxide, which reacts with the lime water to form calcium carbonate, causing it to turn milky. This reaction is commonly used as a test for the presence of carbon dioxide gas. The carbon electrode is commonly used as the negative electrode in dry cells, which are a type of primary battery.
Q 20 – Graphite is a good conductor of electricity where as diamond is not . Explain the reason for the same.
Graphite:
- Graphite is a crystalline allotropic form of carbon.
- It is a soft black lustrous form of carbon that conducts electricity.
Graphite is a conductor but not diamond because:
- In graphite, each carbon atom is linked to three carbon atoms via a covalent bond. The fourth electron is delocalized so it is mobile and can conduct electricity.
- But diamonds have no free electrons because each carbon is four other carbon atoms covalently bonded in a tetrahedral manner.
- So, it has been said that diamonds are bad conductors of electricity.
Hence, graphite is a conductor but diamond is a bad conductor.
Q 21 – Differentiate between the Graphite and Diamond in terms of its characteristics.
Diamond and graphite both are the allotrope of carbon.
| Diamond | Graphite |
| Diamond has a crystalline structure. | Graphite has a layered structure. |
| Diamond is formed by tetrahedral units in which each carbon atom is sp3 hybridized. | Graphite has a planner geometry in which each carbon atom is sp2 hybridized by forming three sigma and one π−bond. |
| Diamond is an insulator of electricity. | Graphite is a good conductor of electricity. |
| Diamond is the hardest naturally occurring substance. | The graphite is soft and has a greasy touch. |
| Diamond is used in jewelry making, construction and surgery. | Graphite is used in stationary and lubricants. |
Q 22 – Define homologous series of carbon compounds. Write the chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their
(i) physical properties, and
(ii) chemical properties.
Homologous series of carbon compounds are so called because any two consecutive members in any series have the common difference of −CH2− and the difference in the molecular mass is 14 amu. In any homologous series,
The two consecutive members of a homologous series are CH3OH and C2H5OH (belong to alcohol)
(i) Alkyl group determines the physical properties of the compound.
(ii) Functional group determines their chemical properties.
Q 23 – Write the molecular formula of first two members of homologous series having functional group
(1) CH3 Cl Chloromethane
(2) CH3 CH2 Cl Chloroethane
Q 24 – Write the molecular formula of first two members of homologous series having functional group —
Soap reacts with Ca2+ and Mg2+ ions present in hard water to form scum.
Q 25 – Unsaturated hydrocarbon gives a yellow flame with lot of black smoke when burnt in oxygen. Give reason.
Unsaturated hydrocarbons have more amount of carbon, therefore burns with smoky flame due to incomplete combustion.
Q 26 – What is a homologous series of carbon compounds?
Homologous series is series of organic compounds which have same functional group and similar chemical properties and each successive member has more — CH2 unit than the previous one.
Q 27 – Write the name and molecular formula of the first member of homologous series of alkynes
HC = CH, Ethyne
Q 28 – Why do alkanes burn with blue flame?
It is because they have less carbon and more hydrogen, therefore, undergo complete combustion and produce blue flame.
Q 29 – State reasons to explain why covalent compounds: a. are bad conductors of electricity? b. have low melting and boiling points?
- Covalent compounds do not form ions, hence they are bad conductor of electricity.
- Covalent compounds have weak intermolecular forces of attraction, therefore, have low melting and boiling points.
Q 30 – Why is hydrogenation? What is its industrial application?
Hydrogenation is a process of adding hydrogen to unsaturated compounds in presence of catalyst like nickel to form saturated hydrocarbons. Industrially, it is used to convert vegetable oils to vegetable ghee.
Q 31 – What are soaps? Why do they form scum with hard water?
Soaps are sodium or potassium salts of fatty acids e.g. sodium stearate. They react with Ca2+ and Mg2+ ions in hard water to form calcium and magnesium salt of fatty acids which are insoluble in water and called scum.
Q 32 – Give reasons for the following:
- Unsaturated hydrocarbons show addition reactions but not saturated hydrocarbons.
- Carbon forms only covalent bonds.
- Unsaturated hydrocarbons have double or triple bonds to which a molecule can be added whereas saturated hydrocarbons have single bonds addition reaction cannot take place.
- It cannot lose four electrons because high energy is required. It cannot gain four electrons because 6 protons cannot hold 10 electrons. Thus it shares four electrons to form covalent bonds and become stable.
Q 33 – Explain giving reasons, why carbon can neither form C 4+ cation nor C4- anion but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points.
Carbon cannot lose four electrons because high energy is needed to remove four electrons. It cannot gain 4 electrons because 6 protons cannot hold 10 electrons. It can share 4 electrons to form covalent bonds. Covalent compounds do not conduct electricity because these do not form ions. They have low melting and boiling points due to weak force of attraction between molecules.
Q 34 – Give reasons for the following observations:
- The element carbon forms a very large number of compounds.
- Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
- Use of synthetic detergents causes pollution of water.
- It is due to tetravalency of carbon and property of catenation shown by carbon to maximum extent.
- Air holes must be kept open fully so that complete combustion of fuel takes place producing blue flame.
- Some of detergents are not bio ¬ degradable, they create water pollution.
Q 35 – Write the name and formula of 2nd member of the series of carbon compounds whose general formula is CnH2 n.
CH2 = CH—CH3 , Propene.
Q 36 – Will micelle formation take place when soap is dissolved in organic solvent?
No, micelles will not be formed in organic solvent.