CBSE Class 10 Science Carbon And Its Compounds Worksheet Set B

Question. CH, The IUPAC name of CH-C-CH-CH, is CH,
(a) 2-ethyl-2-methyl propane
(b) 1, 1, 1-trimethyl propane
(c) 2, 2-demethyl butane
(d) 2, 2-methyl butane

Answer : B

Question. Ethane and ethene can be distinguished by
(a) Br2(l)
(b) Br2 (aq) water
(c) Cl2
(d) I2

Answer : B

Question. Carbon exists in the atmosphere in the form of 
(a) carbon monoxide only
(b) carbon monoxide in traces and carbon dioxide
(c) carbon dioxide only
(d) coal

Answer : B

Question. When ethanoic acid is treated with NaHCO^ the gas evolved is
(a) H₂
(b) CO₂
(c) CH₄
(d) CO

Answer : B

Question. The self linkage property (catenation) is maximum in
(a) carbon
(b) silicon
(c) sulphur
(d) phosphorus

Answer : A

Question. A soap molecule has a
(a) hydrophobic head and hydrophobic tail
(b) hydrophobic head and hydrophilic tail
(c) hydrophilic head and hydrophilic tail
(d) hydrophilic head and hydrophobic tail

Answer : D

Question. Ethanol on complete oxidation gives
(a) acetic acid/ethanoic acid
(b) CO₂ and water
(c) ethanal
(d) acetone/ethanone

Answer : B

Question. Which of the following will give a pleasant smell of ester when heated with ethanol and a small quantity of sulphuric acid?
(a) CH₃COOH
(b) CH₃CH₂OH
(c) CH3OH
(d) CH3CHO

Answer : A

Question. Name the functional group present in CH₃COCH₃.
(a) Alcohol
(b) Carboxylic acid
(c) Ketone
(d) Aldehyde

Answer : C

Question. Why does carbon form compounds mainly by covalent bonding?
(a) There are four electrons in the outermost shell of carbon.
(b) It requires large amount of energy to form C4+ or C4sup>4-.
(c) It shares its valence electrons to complete its octet.
(d) All the above.

Answer : D

Question. 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)

Answer : B

Question. Identify ‘A’ in the following reaction:
CH₃COOH + Na2CO₃ → A + CO₂ + H0O
(a) CH₃COONa
(b) CH2(Na)COOH
(c) NaOH
(d) NaHCO₃

Answer : A

Question. Which of the following belongs to homologous series of alkynes?
C₆H₆, C₂H₆, C2H₄, C₃H₄.
(a) C₆H₆
(b) C₂H₄
(C) C₂H₆
(d) C₃H₄

Answer : D

Question. A hydrocarbon has four carbon atoms. Give its molecular formula if it is an alkene.
(a) C₄H₁₀
(b) C₄H₈
(C) C₄H₆
(d) C₄H₄

Answer : B

Question. The number of isomers of pentane is
(a) 2
(b) 3
(c) 4
(d) 5

Answer : B

Question. In diamond, each carbon atom is bonded to four other carbon atoms to form
(a) a hexagonal array
(b) a rigid three-dimensional structure
(c) a structure in the shape of a football
(d) a structure of a ring

Answer : B

Question. 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

Answer : B

Question. A molecule of ammonia (NH₃) has 
(a) only single bonds
(b) only double bonds
(c) only triple bonds
(d) two double bonds and one single bond

Answer : A

Question. Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of
(a) Addition reaction
(b) Substitution reaction
(c) Displacement reaction
(d) Oxidation reaction

Answer : A

Question. A functional group mainly determines the
(a) physical properties
(b) chemical properties
(c) both
(d) none of these

Answer : B

Question. The blindness and death is caused by consuming adultrated liquor contains.
(a) CH₃OH
(b) CH₃COOH
(c) CH₃COCH₃
(d) CH₃CHO

Answer : A

Question. Structural formula of ethyne is 
(a) CH₃−C≡C−H
(b) H−C≡C−H
(c) H₂−C=C−H₂
(d) H₃−C−C−H₃

Answer : B

Question. Solubility of alcohol in water is due to
(a) low density of alcohol
(b) volatile nature of alcohol
(c) ionisation
(d) hydrogen bonding

Answer : D

Question. C₃H₈ belongs to the homologous series of
(a) Alkynes
(b) Alkenes
(c) Alkanes
(d) Cyclo alkanes

Answer : C

Question. Ethanol reacts with sodium and forms two products. These are 
(a) sodium ethanoate and hydrogen
(b) sodium ethanoate and oxygen
(c) sodium ethoxide and hydrogen
(d) sodium ethoxide and oxygen

Answer : C

Very Short Answers :

Question. What is Allotropy?
Answer: It is a property due to which an element can exist in more than one form which differ in physical properties but have similar chemical properties, e.g., carbon, sulphur, phosphorus, oxygen show allotropy.

Question. What are organic Compounds?
Answer: Those compounds which consist of carbon essentially and hydrogen mostly along with other elements like oxygen, sulphur, nitrogen, halogens, etc., are called organic compounds.

Question. What is Vital Force Theory?
Answer: It was proposed that ‘vital force’ is necessary for formation of these organic compounds. They can only be obtained from living organisms.

Question. Which gas is present in biogas and CNG?
Answer: Methane

Question. Name three allotropes of carbon.
Answer: Diamond, graphite and Buckminster fullerenes

Question. Which is the purest allotrope of carbon?
Answer: Buckminster fullerenes.

Question. Why is graphite soft and slippery?
Answer: Due to weak van der Waals’ forces of attraction between hexagonal layers.

Question. Write the molecular formula of first two members of homologous series with functional group —OH. 
Answer: Methanol (CH₃OH) and Ethanol (CH₃CH₂OH).

Question. Why is diamond hard?
Answer: It is due to strong covalent bonds.

Question. What will be the product formed when carbon is burnt in presence of air?
Answer: Carbon dioxide

Question. Give name of one cyclic hydrocarbon.
Answer: Cyclohexane

Question. Covalent compounds have low melting and boiling point. Why? 
Answer : Covalent compounds have low melting and boiling points because they are made up of electrically neutral molecules. So, the force of attraction between the molecules of a covalent
compound is very weak.

Question. Write the molecular formula of the first two members of the homologous series having functional group —COOH. 
Answer : The molecular formula of the first two members of the homologous series having functional group —COOH is HCOOH and CH₃COOH

Question. What is the difference in the molecular mass of any two adjacent homologues?
Answer : Two successive homologues would differ by one carbon atom and two hydrogen atoms in terms of atoms in their molecules and thus differ by 14 amu in terms of molecular mass.

Question. Write the molecular formula of (i) Methane and (ii) Ethanol. 
Answer : The molecular formula of
(i) Methane: CH₄
(ii) Ethanol: C₂H₅OH

Short Answers :

Question. Explain, giving reason, why carbon neither forms C4+ cations nor C4– anions, but forms covalent compounds which are bad conductors of electricity and have low melting point and low boiling point.
Answer : Carbon could form C4+ cation by losing four electrons, but it would require a large amount of energy to remove four electrons leaving behind a carbon cation with six protons in its nucleus holding on to just two electrons. Carbon could form C4– anion by gaining four electrons, but it would be diffcultforthenucleus with six protons to hold on to ten electrons, that is, four extra electrons. Therefore, carbon forms covalent bonds with other atoms by sharing electron pairs and in this process both atoms attain the noble gas configuration. Covalent compounds are generally poor conductors of electricity since the electrons are shared between atoms and no charged particles are formed. Covalent compounds have generally low melting and boiling points as the intermolecular forces are weak.

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

Question. What are oxidising agents?
Answer : The compounds which add oxygen to other substance are known as oxidising agent.
For example, alkaline potassium permanganate solution and acidified potassium dichromate, both can convert alcohol into carboxylic acid, i.e., ethanoic acid.

Question. How would you name the following compounds:

Answer : (i) Bromo ethane (ii) Methanal
(iii) Hex-1-yne

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. A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Answer : If air is used, incomplete combustion will take place giving a sooty flame and less heat is produced. When pure oxygen is used ethyne burns completely producing large amount of heat and blue flame. This heat is sufficient for a metal to melt and welding is done.

Question. How many structural isomers can you draw for pentane?
Answer : Three structural isomers can be drawn from pentane.
Pentane : C₅H₁₂

Question. What would be the formula and electron dot structure of cyclopentane?
Answer : The formula of cyclopentane is C₅H₁₀.
The electron dot structure is

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. What would be the electron dot structure of carbon dioxide which has the formula CO₂?
Answer : The electron dot structure of CO₂ is

Question. People use variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush or the mixture is agitated in a washing machine. Why is agitation necessary to get clean clothes?
Answer : Soap lowers the surface tension of water. The long chain non-ionic hydrocarbon group in soap gets attached to the oil or grease droplets and loosens them from the fibres of cloth along with the dirt. However this loosening is insufficient to remove the grease with dirt completely. Hence the clothes are agitated to remove the grease droplets completely.

Question. Unsaturated hydrocarbons contain multiple bonds between the two c-atoms and show addition reaction. Give the test to distinguish ethane from ethene. 
Answer : To distinguish between saturated and unsaturated hydrocarbons, a combustion test should be performed. A saturated hydrocarbon undergoes complete combustion and burns with blue flame. Also, it does not leave any residue behind after burning. On the contrary, an unsaturated hydrocarbon undergoes incomplete combustion and burns with yellow flame. Also, it leaves some residue behind after burning. Ethane is a saturated hydrocarbon. Thus, it burns with a blue flame and does not leave a residue behind. Ethene is an unsaturated hydrocarbon. Thus, it burns with a yellow flame and leaves some residue behind.

Question. Why does carbon become stable after sharing four electrons? What type of bond is formed by sharing? 
Answer : The element carbon has atomic number as ' and its electronic configuration is 2,4 and it is tetravalent. Thus, carbon has 4 valence electrons. It can neither gain nor lose 4 electron to acquire the nearest noble gas configuration. Only way is to share the four valence electrons with the electrons of other atoms The type of bond formed by sharing of electrons is covalent bond.

Question. Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Compare the ability of the catenation of the two elements. Give reasons.
Answer : Catenation is the ability of an atom to form bonds with other atoms of the same element. It is exhibited by both carbon and silicon. Carbon exhibits catenation much more than silicon in- fact no other element exhibits the property of catenation to the extent seen in carbon compounds. Silicon forms compounds with hydrogen which have chains of upto seven or eight atoms, but these compounds are very reactive. The carbon- carbon bond is very strong and hence stable. This gives us the large number of compounds with many carbon atoms linked to each other. Carbon has a valency of four and it is capable of bonding with four other atoms of carbon or atoms of some other mono-valent element. The bonds formed by carbon atoms are very strong and do not break easily so carbon compounds are stable.

Question. What are covalent compounds? How are they different from ionic compounds? List any two properties of covalent compounds.
Answer : Covalent compounds are the compounds formed by the sharing of electron pairs between two atoms. Covalent compounds have covalent bonds between atoms. Ionic compounds are formed due to strong electrostatic interactions between ions formed by the transfer of electrons. Ionic compounds have ionic or electrovalent bonds between atoms. Properties of covalent compounds: (1) These compounds have low melting and boiling points. (2) They are generally poor conductors of electricity. (3) Covalent compounds are usually insoluble in water.

Question. What is a homologous series of carbon compounds? List its any two characteristics. Write the name and formula of the next higher homologous of HCOOH.
Answer : Homologous series is a series of carbon compounds in which the hydrogen in a carbon chain is replaced by the same functional group. Characteristics of homologous series are: (1) All members of a homologous series can be represented by the same general formula. For ex, the general formula for alkanes is CnH2n+2, where n is the number of carbon atoms. (2) They have similar chemical properties. (3) Any two adμacent homologues differ by CH2 in their molecular formula. (4) The difference in the molecular masses of any two adjacent homologues is 14 u. (μ) All the compounds belonging to the same homologous series have similar chemical properties. (6) The members of a homologous series show a gradual change in their physical properties with increase in molecular mass.

Question. A student reports the police about the illegal vending of alcohol near his school. He also knew about denatured alcohol. 
i. What is denatured alcohol?
ii. What would happen if somebody consumes denatured alcohol?
Answer :  i. Denatured alcohol is ethanol made unfit for human consumption by adding one or more chemicals (denaturants) to it. Denaturing refers to removing a property from the alcohol (being able to drink it), not to chemically altering or decomposing it, so denatured alcohol contains ordinary ethyl alcohol.
ii. If someone consumes denatured alcohol, it results in coagulation of protoplasm causing acute nausea, blindness and even death.

ii. Pure ethanoic acid is called glacial acetic acid because it form crystals at low temperature. It is a strong acid.

iii. Butanoic acid is a weak acid because it does not ionise completely.

iv. It is a reaction in which ester is heated in presence of a base (mainly NaOH) to give out ethanol & ethanoic acid, this process is used in making of soap.

Ethyl Ethanoate Ethanoic acid Ethanol

 

 

Question : Name the following compounds. 

Answer :  According to the question, Given compounds are

 

 

 

Question : While cooking, if the bottom of the vessels is getting blackened on the outside, it means that: 

Question : Hardness of water is caused by: 

a. All of these
b. Mg(HCO₃)₂
c. CaCl₂
d. CaSO₄

Answer : A 

Explanation: Hardness of water is caused by magnesium and calcium salts.

Calcium and magnesium dissolved in water are the two most common minerals that make water hard. Temporary hardness is a type of water hardness caused by the presence of dissolved bicarbonate minerals (calcium bicarbonate and magnesium bicarbonate).  

 

Question : Which of the following are not straight chain compounds? 

a. A, B and D

b. C and D

c. A and B

d. A and C

Answer : B

Explanation: A and B are straight chain compounds. A has a straight chain of 5 carbon atoms. B has a straight chain of 7 carbon atoms. C and D are not straight chain compounds.

 

Question : What is denatured spirit? 

a. None of these

b. Ethanol only

c. Methanol only

d. Ethanol + Methanol (5%)

Answer : D

Explanation: Alcohol meant for industrial purposes is made unfit for human consumption by adding small amounts (about 5%) of methanol to ethanol. The mixture is known as denatured spirit or denatured alcohol. Addition of small amount of copper sulphate is added to impart a blue colour to denatured spirit so that it can be identified easily.

 

Question : Alcohols can be produced by the hydration of: 

a. Alkenes

b. Alkanes

c. Acids

d. Alkynes

Answer : A 

Explanation: Alcohols can be produced by the hydration of alkenes.

Hydration of alkenes is an addition reaction. The reaction is highly exothermic.

E.g. Ethanol is manufactured by reacting ethene with steam.

 

Question : Write the molecular formula and structural formula of acetaldehyde. 

Answer :   Molecular formula of acetaldehyde : CH₃CHO

Structural formula of acetaldehyde:

 

 

Question : i. What are hydrocarbons? Give examples.

ii. Give the structural differences between saturated and unsaturated hydrocarbons with two examples each.

iii. What is functional group? Give examples of four different functional groups. 

Answer : i. The compounds that are made up of carbon and hydrogen atoms are called hydrocarbons, e.g. methane (CH₄), ethane (CH₂ = CH₂). Ethyne (C₂H₂), cyclohexane (C₆H₁₂), benzene (C₆H₆)etc.

ii. In saturated hydrocarbons, all the four valencies of carbon are satisfied by a single covalent bond while in unsaturated hydrocarbons, double or triple bonds are required to satisfy the valencies of carbon, e.g.

a. Saturated hydrocarbons

Methane (CH₄), Ethane (CH₃ — CH₃)

b. Unsaturated hydrocarbons

Ethene (H₂C = CH₂), Ethyne (HC ≡ CH)

iii. A functional group is an atom or group of atoms that define the structure (or the properties) of organic compounds. The four examples are:

a. -OH Alcohol

b. -COOH Carboxylic acid

c. -CHO Aldehyde

d. -X Halogen 

 

 

Question : i. Write the names of the functional groups in

.

ii. Describe a chemical test to distinguish between ethanol and ethanoic acid.

iii. Write a chemical equation to represent what happens when hydrogen gas is passed through an unsaturated hydrocarbons in the presence of nickel as a catalyst? 

Answer :

i. a. Ketone (R-CO-R)

b. Aldehyde (R-CHO)

ii. Distinguish between ethanol and ethanoic acid:

a. Ethanol does not react with metal carbonate while ethanoic acid reacts with metal carbonates to form salt, water and CO₂.

e.g. 2CH₃COOH + Na₂CO₃ → 2CH₃ COONa + CO₂+ H₂O 

b. Ethanol does not react with NaOH while ethanoic acid reacts with NaOH to form sodium ethanoate and water

e.g. CH₃COOH+NaOH →  CH₃ COONa+ H₂O

c. Ethanol can undrergo oxidation to produce aldehyde and futher it can oxidize to produce acid.

iii. saturated hydrocarbon is obtained as hydrogen gas passed through unsaturated hydrocarbon. The reaction is an example of addition reaction better known by the name of hydrogenation reaction.

 

Question :  Why carbon and its compounds are used as fuels for most applications?
Answer: Carbon and its compounds give large amount of heat on combustion due to high percentage of carbon and hydrogen. They have high optimum ignition temperature with high calorific values and are easy to handle and their combustion can be controlled. Therefore, carbon and its compounds are used as fuels.

Question : What is meant by isomers? Draw the structures of two isomers of butane. Explain why we cannot have isomers of first three members of alkane series?
Answer: Isomers are compounds having the same molecular formula but different structures. Since branching is not possible, isomers are not possible for the first three members of alkanes series.The two isomers of butane, C4H10 are:

Question : State the reason why carbon can neither form C+4 cation nor C-4 anions but forms covalent compound.
Answer: Carbon has atomic number 6. This means that it has 4 electrons in its outermost shell. It needs to gain or lose 4 electrons to achieve noble gas configuration. But it cannot form C+4 cation because the removal of 4 electrons requires a large amount of energy. And also, cannot form C-4 anion as it would be difficult for its nucleus with 6 protons to hold on to 10 electrons. Therefore, Carbon atoms share electrons and form covalent compounds

Question : What is a homologous series? List any of its two features.
Answer: A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group.
Characteristics of homologous series:
1. The members of the homologous series can be represented by a general formula.
2. The successive members differ from each other in the molecular formula by a CH₂ unit.

Question : The element carbon forms a very large number of compounds. Give reason for this fact.
Answer: Carbon forms large number of compounds because of tetravalency and catenation property.
Tetravalency- Carbon has valency 4 to attain noble gas configuration carbon shares 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 : List Any three difference between soap and detergent.
Answer:
soap                                                                   detergent
i) Soaps are sodium salts of fatty acids.        Detergents are sodium salt of sulphonic acids.
ii) Soaps clean well in soft water but             detergents clean well with both with   
do not clean well in hard water                     hard and soft water
Soaps are biodegradable and do not             Some detergents are nonbiodegradable
cause pollution.                                          and cause of pollution