CBSE Class 10 Science Carbon And Its Compounds Worksheet Set G

Question :  What will happen to the litmus solution in carboxylic acid?
Answer : Red litmus remains the same but blue litmus changes to red.

Question : What happens when ethanol burns in air?
Answer : Ethanol burns to form carbon dioxide and water.

Question : A compound has a molecular formula C₂H₆O. It is used as a fuel. Name the compound and name its functional group.
Answer : C₂H₆O is an alcohol, i.e. ethanol C₂H₅OH
Functional group is —OH.

Question : What would be the electron dot structure of carbon dioxide which has the formula CO₂?
Answer: The atomic number (Z) for carbon is six and its electronic configuration is 2, 4. Carbon has four valence electrons.
Each oxygen atom (Z = 8) has six valence electrons (2, 6). In order to complete its octet, the carbon atom shares its four valence electrons with the four electrons of the two
oxygen atoms as follows :
Thus, in carbon dioxide molecule, the carbon atom is linked to two oxygen atoms by two shared pairs of electrons resulting in double bonds on either sides. Both carbon and oxygen
atoms complete their octet as a result of electron sharing.

Question : Why is homologous series of carbon compounds so called? Write the chemical formula of two consecutive members of any homologous series and state the part of these compounds that determines their (i) physical and (ii) chemical properties.
Answer: A homologous series is the family of organic compounds having the same functional group, similar chemical properties but the successive (adjacent) members of the series are differ by a CH₂ unit or 14 mass units.
Consecutive members of the homologous series of alcohols are :
CH₃ OH ] They differ by CH unit.
CH₃ OH
The physical properties are determined by alkyl group/ hydrocarbon part/part other than the functional group.
The chemical properties are determined by functional group such as —OH group.

Question : Define isomerism. Write down the structures and names of isomers of butane.
Answer: Two or more compounds having same molecular formula but different structural arrangements of atoms in their molecules are called isomers. This phenomenon is called
isomerism. 

Question : An element X has a proton number of 15, while element Y has a proton number of 17. Draw a ‘dot-and-cross’ diagram to show all electrons in a molecule formed from elements X and Y.
Answer: Electronic configuration of X : 2, 8, 5 Atom X contributes three electrons for sharing.
Electronic configuration of Y : 2, 8, 7 Each atom of Y contributes one electron for sharing.
Therefore, three atoms of Y contribute three electrons for sharing.
One atom of X will share three pairs of electrons with three atoms of Y to achieve the noble gas configuration.
Both atoms X and Y achieve the electronic configuration of argon (2, 8, 8).

Question : (a) What type of bond holds the two chlorine atoms together in a chlorine molecule?
(b) Briefly describe how this bond is formed.
(c) Draw a ‘dot-and-cross‘ diagram to show the bonding in a chlorine molecule.
Answer: (a) Covalent bond
(b) The two chlorine atoms share one pair of electrons, so that both atoms achieve a noble gas configuration. 

Question : The diagram shows one layer of carbon atoms in the structure of graphite: 

(a) Identify the types of bonding in graphite.
(b) Which property of graphite makes it suitable for use as a dry lubricant? Explain your answer.
Answer: (a) Covalent bonds between carbon atoms in each layer and van der Waals’ forces between the layers of carbon atoms.
(b) Graphite is soft. The layers of carbon atoms can slide and glide over each other because the weak van der Waals’ forces between the layers are easy to overcome.

Question : Explain the nature of the covalent bond using the bond formation in CH₃Cl.
Answer: The molecule of chloromethane (CH₃Cl) consists of three elements i.e., carbon (Z = 6), hydrogen (Z = 1) and chlorine (Z = 17). Carbon atom has four valence electrons (2, 4) ; hydrogen has one (1) while chlorine has seven electrons in the valence shell (2, 8, 7). In order to complete its octet, carbon shares three valence electrons with three hydrogen atoms while one is shared with the electron of chlorine atom. The structure of covalent molecule may be written as follows : 

Question : What is homologous series of compounds?
List any two characteristics of homologous series.
Answer: A series of compounds having similar structures and similar chemical properties in which the successive member differs in their molecular formula by –CH₂ group is called homologous series.
Characteristics :
(a) All the members of homologous series have similar chemical properties.
(b) Any two consecutive members differ in their molecular formula by a –CH₂ group.

Question : Two non-metals A and B combine with each other by sharing of electrons to form compound C.
(a) What is the naturstronge of compound C ?
(b) Will it dissolve in water or organic solvents?
(c) Will it be a good or bad conductor of electricity?
(d) Will it have high or low melting/boiling point ?
Answer: (a) Covalent
(b) Usually soluble in organic solvents
(c) Bad conductor
(d) Usually low melting / boiling point.

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 : 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 : 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 : (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 : Covalent compounds have low melting and boiling point. Why?
Answer: Covalent compounds have low melting and boiling points because the forces of attraction between molecules of covalent compounds are very weak. On applying a small amount of heat these molecular forces break.

Question : What are covalent compounds? Why are they different from ionic compounds? List their three characteristic properties.
Answer: Covalent compounds are those compounds which are formed by sharing of valence electrons between the atoms e.g., hydrogen molecule is formed by mutual sharing of electrons between two hydrogen atoms.
They are different from ionic compounds as ionic compounds are formed by the complete transfer of electrons from one atom to another e.g., NaCl is formed when one valence electron
of sodium gets completely transferred to outer shell of chlorine atom. The characteristic properties of covalent compounds are:
(i) They are generally insoluble or less soluble in water but soluble in organic solvents.
(ii) They have low melting and boiling points.
(iii) They do not conduct electricity as they do not contain ions.

Question : What are covalent bonds? Show their formation with the help of electron dot structure of . Why are covalent compounds generally poor conductors of electricity?
Answer: Covalent bonds are those bonds which are formed by sharing of the valence electrons between two atoms. Electron dot structure of methane is shown in the figure.

Covalent compounds are generally poor conductors of electricity because they do not have tree electrons or ions.

Question : Give reasons for the following:
(i) Element carbon forms compounds mainly by covalent bonding.
(ii) Diamond has high melting point.
(iii) Graphite is a good conductor of electricity.
Answer: (i) As carbon has four valence electrons and it can neither lose nor gain four electrons thus, it attains noble gas configuration only by sharing of electrons. Thus, it forms covalent compounds.
(ii) In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid threedimensional structure. This makes diamond the hardest known substance. Thus, it has high melting point.
(iii) In graphite, each carbon atom is bonded to three other carbon atoms by covalent bonds in the same plane giving a hexagonal array. Thus, only three valence electrons are used for bond formation and hence, the fourth valence electron is free to move. As a result, graphite is a good conductor of electricity.

Question : Write the next homologue of each of the following:
(i) C₂H₄
(ii) C₄H₆
Answer:  (i) C2H4 belongs to alkene series having general formula, CnH₂n.
Thus, next homologue will be C₃H₂×₃ = C₃H₆
(ii) C4H6 belongs to alkyne series having general formula, CnH₂n-2.
Thus, next homologue will be C₅H₂×5-2 = C₅H₈

Question : Name the following compounds:

Answer: 

Question : Write the name and structure of an alcohol with three carbon atoms in its molecule.
Answer:  An alcohol with three carbon atoms in its molecule is propanol. The structure of propanol is

Long Answers