Carbon and Its Compound Class 10 Science Exam Questions

Exam Questions Class 10

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Class 10 Science Exam Questions Carbon and Its Compound

Class 10 Science students should read and understand the important questions and answers provided below for Carbon and Its Compound which will help them to understand all important and difficult topics.

Very Short Answers Type Questions

Question. Write the molecular formula of ethene and draw its electron dot structure.
Answer : Molecular formula of ethene is C2H4.
Electron dot structure of ethene :

Question. Draw electron dot structure of carbon dioxide and write the nature of bonding between carbon and oxygen in its molecule.
Answer : Covalent bond (double bond) is present in between C and O.

Question. List two properties of carbon which lead to the huge number of carbon compounds we see around us, giving reason for each. 
Answer : Two properties of carbon which lead to the huge number of carbon compounds are :
(a) Catenation : It is the ability of carbon to form bonds with other atoms of carbon.
(b) Tetravalency : With the valency of four, carbon is capable of bonding with 4 other atoms. This forms huge number of compounds.

Question. List two chemical properties on the basis of which ethanol and ethanoic acid may be differentiated and explain how.
Unsaturated hydrocarbons contain multiple bonds between two carbon atoms and these compounds show addition reactions. Out of saturated and unsaturated carbon compounds, which compounds are more reactive ? Write a test to distinguish ethane from ethene.
Answer : (a) Ethanol does not react with sodium bicarbonate but ethanoic acid reacts with sodium bicarbonate releasing CO2 gas.
(b) Ethanol does not change the colour of blue litmus paper but ethanoic acid changes the colour of blue litmus to red due to presence of carboxylic acid group.
Unsaturated carbon compounds are more reactive than saturated carbon compounds. Bromine water is decolourized by ethene but there is not change of colour of bromine water with ethane.

Question. In three test tubes A, B and C, three different liquids namely, distilled water, underground water and distilled water in which a pinch of calcium sulphate is dissolved, respectively are taken. Equal amount of soap solution is added to each test tube and the contents are shaken. In which test tube will the length of the foam (lather) be longest ? Justify your answer.
Answer : Length of foam would be longest in test tube A. It is because it does not have any ions, so length of the foam would be longest.

Question. Write the molecular formula of the 2nd and the 3rd member of the homologous series whose first member is methane.
Answer : (a) Ethane C2H6
(b) Propane C3H8

Question. Write the molecular formula of the 2nd and 3rd member of the homologous series whose first member is ethene. 
Answer : (a) Propene : C3H6
(b) Butene : C4H8

Question. Write the molecular formula of the 2nd and 3rd member of the homologous series where the first member is ethyne.
Answer : (a) CH3C ≡ CH (propyne), n = 3
(b) CH3CH2C ≡ CH (Butyne), n = 4

Question. Write the molecular formula of first two members of homologous series having functional group-Cl.
Answer : The general formula for the homologous series of functional group –Cl is CnH2n+1Cl.
(a) CH3Cl
(b) CH3CH2Cl

Question. Write the molecular formula of first two members of homologous series having functional group -Br.
Answer : General formula for the homologous series of Br group is CnH2n+1Br.
(a) CH3Br (Bromomethane)
(b) CH3CH2Br (Bromoethane)

Question. Write the molecular formula of first two members of homologous series having functional group-OH.
Answer : The general formula for the homologous series of functional group-OH is CnH2n+1 OH
(a) CH3OH (Methanol)
(b) CH3CH2OH (Ethanol)

Question. Name the black substance of pencil.
Answer : Graphite.

Question. Out of butter and ground nut oil , which is unsaturated in nature ?
Answer : 
Groundnut oil is unsaturated in nature.

Question. Write the name of the following :

Answer :
(a) Ethene (b) Pentane
(c) Bromopropane (d) 4-chloro-2-pentene
(e) Pent-2-en-1-al

Question. Draw the structure of the following :
(a) Propanoic acid (b) 2-propanol
(c) 1-Iodopropane (d) 3-chlorobutanone
(e) Propyne
Answer :

Question. How would you name the following compounds ?
(a) CH3 — CH2 — Br

Answer : (a) Bromoethane (b) Methanal (c) Hexyne

Question. Write the structural formulae of all the isomers of hexane.
Answer :

Question. Take about 3 ml of ethanol in a test tube and warm it gently in a water bath. What happens when 5% solution of alkaline potassium permanganate drop by drop is added to this ?
Answer : When potassium permanganate is added drop by drop then its colour disappears initially but more of it is added, the colour will remain as such.

Question. How does Acetic acid smells like ?
Answer : Acetic acid smells like vinegar.

Question. What will be formed when ethanoic acid reacts with sodium bicarbonate ?
Answer : Sodium ethanoate, water and carbon dioxide.

Question. Carbon has four electrons in its valence shell. Which type of compounds can be formed by carbon atom and why ? Give any one example of such compounds. 
Answer : Covalent compounds can be formed by carbon atom because carbon atom has 4 valence electrons, hence it is not able to gain four electrons or form C4– ion or lose four electrons or form C4+ ion to attain noble gas configuration. So, it shares electrons to form covalent bonds and the covalent compounds. 
Example : CH4 (methane) compounds.

Question. Which substance is added to denature ethyl alcohol ?
Answer : A small amount of methyl alcohol , pyridine or copper sulphate is added to denature ethyl alcohol.

Question. Why is fullerene so called ?
Answer : Fullerene is so called because it resembles the framework of dome shaped halls designed by American architect Buckminster fuller.

Question. Write the molecular formula of (a) Methane and (b) Ethanol.
Answer : (a) CH4 (b) C2H5OH or C2H6O

Question. Hard water do not produce foam with soap easily. Why ?
Answer : Due to the presence of calcium and potassium salts hard water does not produce foam with soap easily.

Question. You have four beakers A, B, C and D. Out of A and B one has hard water and the other has soft water. Out of C and D one has soap solution and the other has detergent-solution. How would you identify these liquids ?
Answer : On adding soap solution lather will be formed in the beaker containing soft water only. While On adding detergent solution lather will be formed by both hard and soft water in both the beakers.

Question. What do you observe when you add sodium bicarbonate to acetic acid ? How would you identify the gas released in the reaction ? Describe briefly.
Answer : A colourless gas with brisk effervescence will be evolved which turns the lime water milky. When this gas is passed through it.

Question. Write the name of (a) CH4 and (b) CH3COOH.
Answer : (a) Methane
(b) Ethanoic acid or Acetic acid

Question. In a school laboratory the students are studying the properties of ethanoic acid through certain experiments. How can they test its acidic nature ? Give two tests.
Answer : (a) Blue litmus turns red.
(b) On adding solid sodium carbonate or sodium hydrogen carbonate, brisk effervescence is observed.

Question. Write the molecular formula of (a) ethane and
(b) ethanoic acid
Answer : (a) C2H6
(b) CH3COOH

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

Question. If you add a few drops of acetic acid to a test tube containing (i) distillated water and (ii) aqueous solution of sodium hydrogen carbonate, what would you observe ? If a reaction takes place in any one of the above two cases, list its two observations.
Answer : (a) No reaction with distilled water.
(b) Chemical reaction occurs with solution of NaHCO3.
Two observations are :
(i) Evolution of a colourless, odourless gas.
(ii) The gas is evolved with brisk effervescence.

Question. Write the molecular formula of the first two members of the homologous series having functional group C = O.
Answer : CH3COCH3 and CH3COC2H5.

Question. Write the molecular formula of 2nd and the 3rd member of homologous series whose first member is methane.
Answer : (1) CH3—CH3 Ethane
(2) CH3—CH2—CH3 Propane

Question. Write the name and molecular formula of the fourth member of alkane series.
Answer : Name : Butane,
Molecular Formula : C4H10.

Question. Write the formula of first two members of homologous series whose functional group is —CHO.
Answer : 

Carbon and Its Compound Class 10 Science Exam Questions

Question. Which element exhibits the property of catenation to maximum extent and why ?
Answer : Carbon exhibits the property of catenation to maximum extent because of strong C—C bond.

Question. Name the carbon compound which on heating with excess of cone. H2SO4 at 443 K gives ethene.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

Question. Write the molecular formula of 2nd and 3rd member of the homologous series whose first member is ethyne.
Answer : (1) HC / C—CH3 Propyne
(2) HC / C—CH2—CH3 1-Butyne

Question. Write the molecular formula of 2nd and 3rd member of the homologous series whose first member is ethene.
Answer : (1) CH2=CH—CH3 Propene
(2) CH2=CH—CH2—CH3 1-Butene

Question. Will micelle formation take place when soap is dissolved in organic solvent?
Answer : No, micelles will not be formed in organic solvent.

Question. Explain why washing clothes with hard water is not effective.
Answer : Soap reacts with Ca2+ and Mg2+ ions present in hard water to form scum.

Question. Name the functional group present in each of the following compounds:
a. HCOOH
b. C2H5CHO
Answer : 
a. Carboxylic acid
b. Aldehyde

Question. Name the functional group present in each of the following compounds:
a. CH3COCH3
b. C2H5COOH
Answer : 
a. Ketone
b. Carboxylic acid

Question. Draw the structure of simplest ketone.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

Question. Write the next homologue of each of the following:
a. C2H4
b. C4H6
Answer : (1) C3H6, CH2=CH—CH3
(2) C5H8, HC=C—CH2—CH2—CH3

Question. Name the following compounds:

Carbon and Its Compound Class 10 Science Exam Questions

Answer : a. Ethanol
b. Ethanal

Question. Select the saturated hydrocarbons from the following:
C3H6, C5H10, C4H10, C6H14, C2H4
Answer : C4H10, C6H14 are saturated hydrocarbons

Question. Which element exhibits the property of catenation to maximum extent and why?
Answer : Carbon because it can form strong covalent bond with other carbon atoms due to smaller size.

Question. What happens when a small piece of sodium is dropped into ethanol?
Answer : Sodium ethoxide and H2 gas is formed 2C2H5OH + 2Na → 2C2H5ONa + H2

Question. What will you observe on adding a 5% alkaline KMnO4 solution drop by drop to some warm ethanol taken in a test tube? Write the name of the compound formed
during the above chemical reaction.
Answer : 
The purple colour of KMnO4 decolourises and ethanoic acid will be formed C2H5OH →Alk.KMNO4 + CH2OOH ethanol ethanoic acid

Question. A colourless gas X has a formula C3H6. It decolourises bromine water. Write the chemical formula of ‘X’.
Answer : CH2=CH—CH3, Propene

Question. Draw the structural formula of methanoic acid.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

Question. Butanone has four carbon per molecule of a compound. Name the functional group present in it.
Answer : Ketone

Question. Name the following compound:
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

1-Hexyne

Question. Write the name and formula of the first member of series of carbon compound having functional group —CHO.
Answer : 

Carbon and Its Compound Class 10 Science Exam Questions

Question. Write the name and formula of the 2nd member of the series of carbon compounds whose general formula is CnH2n+1—OH.
Answer :  C2H5OH, Ethanol

Question. Write the name and formula of 2nd member of the series of carbon compounds whose general formula is CnH2n.
Answer :  CH2=CH—CH3, Propene

Question. A molecule of ammonia has the formula NH3. Predict the total number of bonds present around nitrogen atom.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

Question. Write the number of covalent bonds in the molecule of ethane.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions

Question. Write the next homologue of propanol CH3CH2CH2OH and butanal CH3CH2CH2CHO.
Answer : a. CH3CH2CH2CH2OH, Butanol
b. CH3CH2CH2CH2CHO, Pentanal

Question. Unsaturated hydrocarbon gives a yellow flame with lot of black smoke when burnt in oxygen. Give reason.
Answer : Unsaturated hydrocarbons have more amount of carbon, therefore burns with smoky flame due to incomplete combustion.

Question. Write molecular formula of alcohol which can be derived from butane.
Answer : CH3CH2CH2CH2OH, 1-Butanol

Question. State the valency of each carbon atom in (i) an alkane and (ii) an alkyne.
Answer : i. The valency of ‘C’ in alkane is 4.
ii. The valency of ‘C’ in alkyne is also 4.

Question. Write the molecular formula of benzene and state the number of double bonds in its structure.
Answer :

Carbon and Its Compound Class 10 Science Exam Questions


These are 3 double bonds.

Question. Carbon has four electrons in its valence shell. How does carbon attain stable electronic configuration?
Answer : Carbon can share four electrons to acquire stable electronic configuration.

Question. Write the name and formula of 2nd member of homologous series having general formula CnH2n.
Answer : CH2=CH—CH3 is second member of alkene.

Question. Write the name and formula of 2nd member of homologous series having general formulaCnH2n+2 .
Answer : CH3—CH3, Ethane

Question. Write the name and formula of 2nd member of homologous series having general formula CnH2n+2 .
Answer : HC ≡ C—CH3, Propyne

Question. Write the name of each of the following functional groups:

Carbon and Its Compound Class 10 Science Exam Questions

Answer : a. Alcohol
b. Ketone

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 = C3H62
(ii) C4H6 belongs to alkyne series having general formula, CnHn–2.
Thus, next homologue will be C5H2 × 5 – 2 = C5H8

Question:  Name the following compounds :
(a) CH3 — CH2 — OH
            H
             l 
 (b) CH3 C= O
Answer:

Carbon and Its Compound Class 10 Science Exam Questions

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. e structure of propanol is : 

Carbon and Its Compound Class 10 Science Exam Questions

Question: Select saturated hydrocarbons from the following :
C3H6; C5H10; C4H10; C6H14; C2H4
Answer: Saturated hydrocarbons have general formula, CnH2n+2.
Among the given compounds only C4H10 and C6H14 satisfy the above formula. Thus, these are saturated hydrocarbons.

Question:  Write the name and structure of an aldehyde with four carbon atoms in its molecule.
Answer: An aldehyde with four carbon atoms is butanal and its structure is :

Carbon and Its Compound Class 10 Science Exam Questions

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

Carbon and Its Compound Class 10 Science Exam Questions

Question: Which element exhibits the property of catenation to maximum extent and why?
Answer:
 Carbon has the unique ability to form bonds with other atoms of carbon, giving rise to large molecules. is property is called catenation. Carbon shows catenation due to its small size and stronger carbon-carbon bond strength.

Question:  What is homologous series of carbon compounds? 
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.

Question:  Write the name and molecular formula of the fourth member of alkane series.
Answer:
 The general formula of the alkane series is CnH2n+2. For fourth member of alkane series,
n = 4
∴ C4H2 × 4 + 2 = C4H10 i.e., butane.

Question: State two characteristic features of carbon which when put together give rise to a number of carbon compounds. 
Answer:
Due to catenation and tetravalency, carbon gives rise to a number of carbon compounds.

Question: Write the structural formula of chloroethane.
Answer:

Carbon and Its Compound Class 10 Science Exam Questions

Question: Give reasons for the following observation: The element carbon forms a very large number of compounds.
Answer:
Due to catenation and tetravalency, carbon gives rise to a number of carbon compounds.

Question: Butanone is a four-carbon per moleculecompound. Name the functional group present in it.
Answer:

Carbon and Its Compound Class 10 Science Exam Questions

Question: Name the process by which unsaturated fats are changed to saturated fats. 
Answer:
Hydrogenation is the process in which unsaturated fats are changed to saturated fats.

Question: Write the names of the functional groups in :


Answer:

Question: Name the following compound : 
Answer:

Question: Write the chemical equation to show what happen when methane is treated with chlorine in the presence of sunlight ?

Answer: When methane is treated with chlorine in the presence of sunlight then substitution reaction takes place. In this, chlorine replaces the hydrogen atom of methane.
CH4 Cl2 Sunlight→ CH3Cl +HCl

Question: Write the respective chemical reaction to show what happens when methane is burnt in presence of oxygen? 
Answer:
When methane is burnt in presence of oxygen then carbon dioxide will be produced.

Question: Write one chemical equation to represent the following type of reaction of organic substances : substitution.
Answer:
Substitution : In this type of reaction one or more hydrogen atoms of a hydrocarbon is replaced by some other atoms.

Question: Give reason for the following : Acetylene burns with a sooty flame. 
Answer:
The formula of acetylene is HC CH. It is an unsaturated hydrocarbon where carbon content is more than the hydrogen content. Hence, carbon is not completely burnt and the unburnt carbon deposits as a soot.

Question: Give reasons for the following observation : Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the flame.
Answer:
Air holes of a gas burner have to be adjusted when the heated vessels get blackened by the name as to get sufficient supply of oxygen (air) for complete combustion.

Question: Give reason for the following : Kerosene does not decolourise bromine water while cooking oils do. 
Answer:
Cooking oils (unsaturated compounds) decolourise bromine water due to formation of addition products whereas kerosene (saturated compound) does not decolourise bromine water.

Question: (i) What would be observed on adding a 5% solution of alkaline potassium permanganate solution drop by drop to some warm ethanol taken in a test tube?
(ii) Write the name of the compound formed during the chemical reaction?
Answer:
(i) Colour of KMnO4 will get discharged. (ii) Th e chemical compound formed is ethanoic acid

Question: Draw  the structure for ethanoic acid molecule, CH3COOH.
Answer:
Structure of ethanoic acid is

Question: Name the gas evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?
Answer:
When ethanoic acid is added to sodium carbonate, CO2 gas is evolved which turns lime water milky.

Question: What happens when a small piece of sodium is dropped into ethanol?
Answer:
When a small piece of sodium is dropped into ethanol then hydrogen gas is liberated which burns with a pop sound.

Short Questions type Answer:

Question. Which compounds are called (a) alkanes, (b) alkenes and (c) alkynes ? C4H10 belongs to which of these ?
Draw two structural isomers of this compound.
Answer : (a) The hydrocarbons in which carbon atoms are connected by only single covalent bonds are called alkanes.
(b) The hydrocarbons in which carbon atoms are connected by double bond are called alkene.
(c) The hydrocarbons in which carbon atoms are connected by triple bond are called alkynes.
C4H10 belongs to alkane.
Structural Isomers of C4H10 :

Question. Mention the essential material (chemicals) to prepare soap in the laboratory. Describe in brief the test of determining the nature (acidic/alkaline) of the reaction mixture of saponification reaction.
Answer : The essential chemicals required to prepare soap in the laboratory are oil and sodium hydroxide solution. In order to determine the nature of the reaction mixture of saponification reaction, we dip red litmus paper into it which will turn blue after a while indicating that it is a basic mixture.

Question. Write the structural formula of ethanol. What happens when it is heated with excess of conc. H2SO4 at 443 K ?
Write the chemical equation for the reaction stating the role of conc. H2SO4 in this reaction.
Answer : Structural formula of ethanol is :
CH3CH2OH
When ethanol is heated with excess of conc. H2SO4 at 443 K it results in the dehydration of ethanol to give ethene.

Role of conc. H2SO4 : Conc. H2SO4 acts as a dehydrating agent which removes water from the ethanol.

Question. Distinguish between esterfication and saponification reaction with the help of the chemical equations for each. State one use of each (a) esters, and (b) saponification process.
Answer : Esterification is opposite of saponification. In esterification :

Whereas in saponification :
RCOOR’ + NaOH → RCOONa + R’OH
(a) Uses of Esters : Esters are used in making perfumes.
(b) Uses of saponification reaction : Used in making soaps and soap products on a large scale.

Question. Two carbon compounds X and Y have the molecular formula C4H8 and C5H12 respectively. Which one of these is most likely to show addition reaction ?
Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer : X = C4H8 is an alkene.
Y = C5 H12 is an alkane.
X being an alkene i.e., butene is unsaturated compound and will show addition reaction as they have free electrons for bonding.

Question. What happens when (write chemical equation in each case)
(a) ethanol is burnt in air ?
(b) ethanol is heated with excess conc. H2SO4 at 443 K ?
(c) a piece of sodium is dropped into ethanol ?
Answer : (a) CH3CH2OH + 3O2 → 2CO2 + 3H2O + Heat + light

Question. Explain esterification reaction with the help of a chemical equation. Describe an activity to show esterification.
Answer : The reaction of carboxylic acid with alcohol forms an ester. This process of formation of ester is called esterification.
CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O
Activity :
(a) Take 1 ml of ethanol and 1 ml of glacial acetic acid in a boiling tube and mix the contents well.
(b) Add few drops of conc. H2SO4 to it.
(c) Warm the contents on a water bath for a few minutes.
(d) Now pour the solution in a beaker containing 20-50 ml of water.

(e) A sweet fruity smell indicating formation of an ester is observed.

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 catenation of the two elements. Give reasons.
Answer : Carbon has the maximum capacity of catenation. The reason for this is the smaller size of of carbon which makes the C–C bonds strong. The size of silicon is greater than Carbon. This makes Si—Si bonds comparatively weaker than C – C bond.

Question. Two carbon compounds X and Y have the molecular formula C3H6 and C4H10 respectively. Which one of the two is most likely to show addition reaction ?
Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer : C3H6 is propene i.e., unsaturated hydrocarbon. C4H10 is butane i.e., saturated hydrocarbon. Thus, propene being unsaturated shows addition reaction.

Question. Why does micelle formation takes place when soap is added to water ? Will a micelle form in other solvents such as ethanol also ?
Answer : Soap may be represented by the formula RCOONa where R is an alkyl group which represents long chain of carbon with fifteen or more atoms. Oil drops containing dirt particles and water do not mix. Soap helps in their mixing by reducing interfacial tension or friction. Actually it forms a sort of bridge between oil drops and water in which the alkyl portion (hydrophobic end) point towards oil drop while other portion (hydrophilic end) is directed towards water. 
This is known as micelle formation. Thus, soap helps in the formation of a stable emulsion between oil and water. Ethanol and other similar solvents which are of organic nature do not help in micelle formation because soap is soluble in them.

Question. What is hydrogenation ? What is its industrial application ?
Answer : Hydrogenation is the process of addition of hydrogen. Unsaturated hydrocarbons are added with hydrogen in the presence of palladium and nickel catalysts to give saturated hydrocarbons 

Industrial application : Used in the hydrogenation of vegetables oils, which contain long chains of unsaturated carbons.

Question. The molecular formula of two carbon compounds are C4H8 and C3 H8. Which one of the two is most likely to show addition reaction ? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer : (a) C4H8 : Butene- alkene (unsaturated hydrocarbon)
(b) C3H8 : propane-alkane (saturated hydrocarbon)
C4H8 i.e., butene shows addition reaction as it is unsaturated hydrocarbon

Question. (a) What is the atomic number of carbon. Write its electronic configuration.
(b) What type of chemical bonds re formed by carbon ? Why ?
(c) Name the three allotropic forms of carbon.
Answer : (a) The atomic number of carbon is 6. Its electronic configuration is 2, 4.
(b) Carbon forms covalent bonds because it can achieve the inert gas electron arrangement only by sharing of electrons.
(c) Diamond, graphite and buckminster fullerene.

Question. Preetam and Satnam were revising the chapter on Carbon and its compounds. Preetam said, “It is quite amazing that diamond and graphite are both allotropes of carbon but the two have completely different properties. While diamond is the hardest material, graphite is soft”.
(a) What is the cause of different nature of these two substances ?
(b) What is the core of lead pencils ?
Answer :
(a) The difference in nature of the two substances is due to structure of the two allotropes. In diamond, each carbon atom is bonded to four other carbon atoms forming a rigid three dimensional structure. In graphite, each carbon atom is bonded to three other carbon atoms in the same plane, giving a hexagonal array. The fourth valency is satisfied by weak bonding between carbon atoms in one plane with the corresponding atoms in the other planes above and below a particular plane.
(b) Lead pencil is a monomer. Actually it is graphite which the core of the pencil is made of.

Question. What happens when hydrogen is added to a vegetable oil in the presence of nickel ? Name the reaction and write one difference between the physical property of the vegetable oil and the product obtained in this reaction. Write the role of nickel in this reaction.
Answer : When hydrogen is added to a vegetable oil in the presence of nickel the vegetable oil is converted into saturated fat. The reaction is called hydrogenation reaction. Vegetable oil is liquid whereas saturated fat is solid at room temperature. Nickel acts as the catalyst in this reaction.

Question. (a) Give the general name of the class of compounds having the general formula CnH2n–2. Write name of the first member of this homologous series.
(b) The general formula of a homologous series of carbon compounds is CnH2n. Write the molecular formulae of the second and fifth members of the series.
(c) Write the molecular formulae of the third and fourth members of homologous series of carbon compounds represented by the general formula CnH2n+2.
Answer : (a) Alkynes, CnH2n–2
First member : Ethyne : C2H2
(b) Second member : C3H6
Fifth member : C5H12
(c) Third member : C3H8
Fourth member : C4H10

Question. An organic compound A having the molecular formula C3H8O is a liquid at room temperature. The organic liquid A reacts with sodium metal to evolve a gas which burns causing a little explosion. When the organic liquid A is heated with concentrated sulphuric acid at 170°C, it forms a compound B which decolourises bromine water. The compound B adds on one molecule of hydrogen in the presence of Ni as catalyst to form compound C which gives substitution reactions with chlorine.
(a) What is compound A ?
(b) What is compound B ?
(c) What type of reaction occurs when A is converted into B ?
(d) What is compound C ?
(e) What type of reaction takes place when B is converted into C ?
Answer : (a) A is propanol, CH3–CH2–CH2OH.
(b) B is propene, CH3CH = CH2.
(c) Dehydration reaction.
(d) C is propane, CH3CH2–CH3.
(e) Addition reaction.

Question. Differentiate between Diamond and Graphite.
Answer :

Question. Give reason why carbon can neither form C4+ cations nor C4– anions, but forms covalent compounds which are bad conductors of electricity and have low melting and boiling points ? 
Answer : Carbon cannot form C4+ cation because removal of 4 electrons from a carbon atom would require a large amount of energy. While it cannot form C4- anion because it would be difficult for the nucleus with 6 protons to hold on to 10 electrons. Hence, carbon atoms share electrons forming covalent compounds. Covalent compounds do not form ions, charged particles and therefore do not conduct electricity and the Inter molecular forces of attraction are weak, hence they have low melting and boiling points.

Question. Give reasons :
(a) Why is pure ethanoic acid known as glacial acetic acid ?
(b) Why is ethanol used as antifreeze ?
(c) What is gasol ? 
Answer : 
(a) Pure ethanoic acid has a low freezing point. It freezes and looks like glaciers.
(b) Ethanol mixed with water freezes at temperatures lower than water. Thus, a mixture of water and ethanol is used in radiators of cars in cold countries.
(c) Gasol is a mixture of petrol and alcohol.

Question. What are covalent compounds ? How are they different from ionic compounds ? List any two properties of covalent compounds.
Answer : The compounds that are formed due to sharing of electrons between two atoms of compounds are having covalent bonds.
Ionic compounds are formed due to transfer of electrons from one atom to another while covalent compounds are formed by the sharing of electrons :
The two properties of covalent compounds are :
(a) Covalent compounds are poor conductors of electricity
(b) They have low melting and boiling point.

Question. What is a homologous series of carbon compounds ?
Write the formula of the fourth and fifth member of a homologous series having general formula CnH2n + 1 OH. List two differences in physical properties found in the two consecutive members of a homologous series.
Answer : A group of organic compounds having the same functional group and similar structures in which two successive members differ by –CH2 group. C4H9OH and C5H11OH.
(a) They differ by a mass of 14 u and show gradation in properties.
(b) Their boiling point increases with increase in molecular mass.

Question. Complete the following chemical equations :
(a) CH3COOH + Na2CO3
(b) CH3COOH + NaOH →
(c) CH3COOC2H5 + NaOH →
Answer : (a) CH3COOH + Na2CO3 → 2CH3COONa + H2O + CO2
(b) CH3COOH + NaOH → 2CH3COONa + H2O
(c) CH3COOC2H5 + NaOH → CH3COONa + C2H5OH

Question. A student is studying the properties of acetic acid in his school laboratory. List two physical and two chemical properties which he must observe and note in his record book. 
Answer : Physical properties :
(a) Smell like vinegar,
(b) Colourless liquid.
Chemical properties :
(a) turns blue litmus red,
(b) gives brisk effervescence with sodium carbonate.

Question. Write the molecular formula of benzene and draw its structure. List in tabular form the two properties in which covalent compounds differ from ionic compounds. 
Answer : C6H6 is the molecular formula of benzene.

Question. Ethanoic acid reacts with absolute ethanol in the presence of Conc. H2SO4 to form a compound.
(a) Write the smell and class of compounds to which this compound belong.
(b) Write the chemical equation for the reaction and state the role of Conc. H2SO4 in the reaction.
(c) Write one use of the product of this reaction.

Answer :
(a) Pleasant or fruity smell and it belongs to Esters.

Conc. H2SO4 acts as a catalyst or dehydrating agent.
(c) Used in perfume industry and as flavouring agent.

Question. Name two oxidising agents that are used for the conversion of alcohols to acids. Distinguish between ethanol and ethanoic acid on the basis of (a) litmus test, and (b) reaction with sodium hydrogen carbonate.
Answer : Alkaline KMnO4 and Acidified KrCr2O7 are used as oxidising agents to convert alcohols to acids.
(a) Ethanol does not affect litmus paper whereas Ethanoic acid turns blue litmus red.
(b) Ethanol does not react with NaHCO3 whereas Ethanoic acid gives brisk effervesence with the evolution of colourless gas CO2.

Question. An organic compound ‘P’ is a constituent of wine. ‘P’ on reacting with acidified K2Cr2O7 forms another compound ‘Q’. When a piece of sodium is added to ‘Q’ a gas ‘R’ evolves which burns with a pop sound. Identify P, Q and R and write the chemical equations of the reactions involved.
Answer : P — Ethanol, Q — Ethanoic acid, R — Hydrogen

Question. (a) Define the term functional group. Identify the functional group present in :

(b) What happens when 5% alkaline KMnO4 solution is added drop by drop to warm ethanol taken in a test tube ? State the role of alkaline KMnO4 solution in this reaction.
Answer : (a) Functional group is the hetero atom or group of atoms attached to the carbon chain, which gives specific properties to the compound.
(i) Aldehyde group (ii) Carboxylic acid.
(b) Acetic acid or Ethanoic acid is formed Alkaline KMnO4 solution act as an oxidizing agent.

Question: Write the chemical equations to show what happens when
(i) an ester reacts with a base?
(ii) ethanol reacts with ethanoic acid in the presence of sulphuric acid?
Answer: (i) When an ester reacts with the base then it gives sodium salt of carboxylic acid and an alcohol. It is known as saponification reaction.

(ii) Carboxylic acids react with alcohols in the presence of a little concentrated sulphuric acid to form pleasant smelling esters. This reaction is called esterification reaction.

Question: Describe a chemical test to distinguish between ethanol and ethanoic acid.
Answer: Chemical test for ethanol and ethanoic acid is : Ethanoic acid reacts with Na2CO3 or NaHCO3 to give brisk effervescence of CO2 gas.

While ethanol does not react with Na2CO3 or NaHCO3.

Question: How would you distinguish experimentally between an alcohol and a carboxylic acid on basis of a chemical property?
Answer:

Question: The molecular formula of two carbon compounds are C4H8 and C3H8. Which one of the two is most likely to show addition reaction? Justify your answer. Also give the chemical equation to explain the process of addition reaction in this case.
Answer: All unsaturated hydrocarbons (containing double or triple bonds) have tendency to get converted to saturated hydrocarbons (single
bonds) by adding small molecules such as hydrogen (H2), halogens (X2), etc. Such reactions are called addition reactions.
Compound X i.e. C4H8 belongs to alkene series (CnH2n) while compound Y i.e. C5H12 belongs to alkane series
(CnH2n + 2). Thus, compound X will undergo addition reaction.

Question: What is an oxidising agent? What happens when an oxidising agent is added to propanol?
Explain with the help of a chemical equation.

Answer: The substance that supply oxygen in a reaction for oxidation is called oxidising agent e.g., potassium permanganate, potassium
dichromate, etc. When propanol is heated with alkaline KMnO4, it gets oxidised to propanoic acid.  EMAGE 66

Question: Write the name and general formula of a chain of hydrocarbons in which an addition reaction with hydrogen is possible. State the essential condition for an addition reaction. Stating this condition, write a chemical equation giving the name of the reactant and the product of the reaction.
Answer: Alkene, having general formula as CnH2n and alkyne, having general formula as CnH2n – 2 are the class of hydrocarbons in which addition reaction is
possible.
The essential conditions for addition reaction are :
(i) Presence of unsaturated hydrocarbon.
(ii) Presence of catalyst such as Ni/Pt/Pd.
Let us take an example of ethene. It undergoes addition reaction with hydrogen when it is heated in the presence of nickel catalyst to form ethane.
The reaction is known as hydrogenation

Question: Draw the electron-dot structure for ethyne. A mixture of ethyne and oxygen is burnt for welding. In your opinion, why cannot we use a mixture of ethyne and air for this purpose?
Answer:The formula for ethyne is C2H2 and its electron dot structure is :


A mixture of ethyne and oxygen is burnt for welding so that complete oxidation of ethyne takes place. If in place of oxygen, air is taken which
contains less amount of oxygen then incomplete combustion of oxygen takes place and temperature required for welding will not be attained.

Question: Complete the following chemical equations :
Answer:

Question: Complete the following chemical equations:
Answer: 

Question: Write the structural formula of ethanol. What happens when it is heated with excess of conc. H2SO4 at 443 K? Write the chemicalequation for the reaction stating the role of conc. H2SO4 in this reaction.
Answer:The structural formula of ethanol (C2H5OH) is

When ethanol is heated with conc. H2SO4 at 443 K then it loose a water molecule to form unsaturated alkene (ethene) as a product.

Question:Distinguish between Esterification and saponification reaction with the help of the chemical equations for each. State one use of each (i) esters, and (ii) saponification process.
  Answer: 

Use of esters : They are used for making perfumes
or used as artificial avouring substances.
Use of saponification process : This process is used in making soaps.

Question: (a) What is a homologous series of compounds? List any two of its characteristics.
(b) What is the next higher homologue of C3H7OH? What is its formula and what is it called?
Answer: (a)  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.
Two characteristics of homologous series :
(i) The successive compounds of the homologous series diffier by —CH2 unit i.e. 14 mass units.
(ii) Each homologous series belongs to similar class of compounds which shows the same properties.
(b) Next higher homologue of C3H7OH is C4H9OH i.e. butanol.

Question: Explain Esterification reaction with the help of a chemical equation. Describe an activity to show Esterification. 
Answer:(ii) Carboxylic acids react with alcohols in the presence of a little concentrated sulphuric acid to form pleasant smelling esters. This reaction is called esterification reaction.
(ii) Carboxylic acids react with alcohols in the presence of a little concentrated sulphuric acid to form pleasant smelling esters. This reaction is called esterification reaction.

Question: When ethanol reacts with ethanoic acid in the presence of conc. H2SO4, a substance with fruity smell is produced.
Answer the following :
(i) State the class of compounds to which the fruity smelling compounds belong. Write the chemical equation for the reaction and write the chemical name of the product formed.
(ii) State the role of conc. H2SO4 in this reaction.
Answer: (i) When ethanol reacts with ethanoic acid in presence of conc. H2SO4 ethyl ethanoate is formed which belongs to the class of ester
compounds, having fruity smell. 

(ii) The above reaction is called esterification which occurs in presence of conc. H2SO4 which acts as a dehydrating agent and helps in the
removal of water. Conc. H2SO4 also acts as a catalyst to speed up the reaction.

Question: On dropping a small piece of sodium in a test tube containing carbon compound ‘X’ with molecular formula C2H6O, a brisk effervescence is observed and a gas ‘Y’ is produced. On bringing a burning splinter at the mouth of the test tube the gas evolved burns with a pop sound. Identify ‘X’ and ‘Y’. Also write the chemical equation for the reaction. Write the name and structure of the product formed, when you heat ‘X’ with excess conc. sulphuric acid. 
Answer: Ethanol reacts with sodium to form sodium ethoxide and hydrogen gas is liberated which burns with a pop sound.

Thus, compound X is ethanol and gas Y is hydrogen gas. When ethanol is heated with excess of concentrated sulphuric acid then it gets dehydrated to form ethene.

Question: Write three different chemical reactionsshowing the conversion of ethanoic acid to sodium ethanoate. Write balanced chemical equation in each case. Write the name of the reactants and the products other than ethanoic acid and sodium ethanoate in each case.
Answer:Ethanoic acid reacts with Na2CO3 to form sodium ethanoate and CO2 gas is liberated.

With sodium hydrogen carbonate it forms sodium ethanoate.

Question:  Write the name and molecular formula of an organic compound having its name suffixed with ‘ol’ and having two carbon atoms in its molecule. Write balanced chemical equation to indicate what happens when this compound is heated with excess conc. H2SOand the name of main product formed. Also state the role of conc. H2SO4 in the reaction.
Answer: Those organic compounds having suffx ‘ol’ are alcohols. As the alcohol having two carbon atoms in its molecule so, it is ethanol.

The structural formula of ethanol (C2H5OH) is

When ethanol is heated with conc. H2SO4 at 443 K then it loose a water molecule to form unsaturated alkene (ethene) as a product. 

Question:  An organic compound ‘P’ is a constituent of wine. ‘P’ on reacting with acidified K2Cr2Oforms another compound ‘Q’. When a piece of sodium is added to ‘Q’, a gas ‘R’ evolves which burns with a pop sound. Identify P, Q and R and write the chemical equations of the reactions involved.
Answer: ‘P’ is ethanol which is a constituent of wine. Ethanol on reacting with acidified potassium dichromate (K2Cr2O7) solution gives ethanoic acid

When a piece of sodium is added to ethanoic acid then sodium salt of ethanoic acid is formed with the liberation of hydrogen gas which burns with a pop sound.

Question: Name the compound formed when ethanol is heated in excess of conc. sulphuric acid at 443 K. Also write the chemical equation of the reaction stating the role of conc. sulphuric acid in it. What would happen if hydrogen is added to the product of this reaction in the presence of catalyst such as palladium or nickel? 
Answer: The structural formula of ethanol (C2H5OH) is

When ethanol is heated with conc. H2SO4 at 443 K then it loose a water molecule to form unsaturated alkene (ethene) as a product If hydrogen is added to ethene in presence of palladium or nickel catalyst then one atom of hydrogen adds to each carbon atom of ethene to form ethane. 

Question:  List two tests for experimentally distinguishing between an alcohol and a carboxylic acid and describe how these tests are performed.
Answer: Tests for distinguishing between an alcohol and a carboxylic acid are :
(i) Litmus test : When we place a drop of carboxylic acid on blue litmus paper it turns red while alcohol will not change the colour of blue litmus paper.
(ii) Sodium hydrogen carbonate test/sodium carbonate test : If a pinch of NaHCO3 or Na2COis added to two test tubes containing alcohol
and carboxylic acid respectively. Then test tube containing carboxylic acid will show the evolution of colourless gas with brisk effervescence while test tube containing alcohol does not show any reaction.

Question:  Write chemical equations to describe two examples of difierent oxidations of ethanol. 
Answer: Addition of oxygen to any substance is called oxidation.Ethanol gets oxidised to ethanoic acid as

When ethanol is heated with alkaline solution of potassium permanganate then oxidation of ethanol takes place to form ethanoic acid.

Two physical properties of ethanol are :
1. It is liquid at room temperature.
2. It is soluble in water in all proportions. Two uses of ethanol are :
1. It is used as a liquor for drinking purpose.
2. It is a good solvent and hence, it is used in medicines such as tincture of iodine, cough syrup and many tonics.

Question: What are esters? How are they prepared? List two uses of esters.
Answer: Esters are generally volatile liquids which
have pleasant fruity smell.Esters are prepared when a carboxylic acid reacts with an alcohol in the presence of small amount of concentrated H2SO4. For example, when ethanoic acid reacts with ethanol it forms an ester (i.e. ethyl ethanoate)

Uses of ester :
It is used in making perfumes.
It is used in making artificial avours and essences used in ice-creams, sweets and cold drinks.

Question: An organic acid X is a liquid which often freezes during winter time in cold countries, has the molecular formula C2H4O2. On warming it with ethanol in the presence of a few drops of concentrated sulphuric acid a compound Y with a sweet smell is formed.
(i) Identify X and Y.(ii) Write a chemical equation for the reaction involved
Answer: ‘X’ is CH3COOH (ethanoic acid) which freezes during winter time in cold countries. On warming ethanoic acid with ethanol in presence of a few drops of concentrated sulphuric acid, a fruity smelling ester is formed.

Question:  A carbon compound ‘P’ on heating with excess conc. H2SO4 forms another carbon compound ‘Q’ which on addition of hydrogen in the presence of nickel catalyst forms a saturated carbon compound ‘R’. One molecule of ‘R’ on combustion forms two molecules of carbon dioxide and three molecules of water. Identify P, Q and R and write chemical equations for the reactions involved.
Answer: When ethanol is heated with excess of concentrated H2SO4 it gets dehydrated to formethene.

When ethene is heated with hydrogen in presence of nickel catalyst it forms ethane

Ethane on oxidation gives two moles of carbon dioxide and three moles of water.

Question. You have four test tubes A, B, C and D filled with aqueous solution of same concentration but of different salts. In A solution of NaCl, B solution of CaCl2, C solution of MgCl2 and D solution of KCl is filled. If you add equal amounts of a soap solution to each test tube and shake the contents well, in which of the test tubes will scum (insoluble substance) be obtained ? 
(a) A and B
(b) B and C
(c) C and D
(d) A and D

Answer

B

Question. The name of the compound CH3— CH2— CHO is :
(a) Propanal
(b) Propanone
(c) Ethanol
(d) Ethanal

Answer

A

Question. While studying the saponification reaction, what do you observe when you mix an equal amount of colourless vegetable oil and 20% aqueous solution of NaOH in a beaker ?
(a) The colour of the mixture has become dark brown.
(b) A brisk effervescence is taking place in the beaker.
(c) The outer surface of the beaker has become hot.
(d) The outer surface of the beaker has become cold.

Answer

C

Question. You have neem oil in a beaker. In order to study saponification reaction, which of the following chemical substances would you add to this oil ?
(a) 20% Ca(OH)2
(b) 20% NaOH
(c) 30% Mg(OH)2
(d) 10% Ca(OH)2

Answer

B

Question. You are asked to prepare hard water in your laboratory.
Select a group from the following groups of salts, any salt of which you may dissolve in distilled water to obtain hard water.
(a) NaCl; Na2SO4; KCl
(b) NaCl; CaCl2; KCl
(c) CaCl2; CaSO4; MgSO4
(d) Na2SO4; CaSO4; MgSO4.

Answer

C

Question. Some students studied the physical properties of acetic acid and noted down their observations. Which of the following observations is correct ?
(a) Smells like rose and soluble in water.
(b) Smells like burning plastic and insoluble in water.
(c) Smells like vinegar and soluble in water.
(d) Smells like rotten egg and soluble in water.

Answer

C

Question. Select the correct statement about the properties of acetic acid. 
(a) It smells like vinegar and turns red litmus to blue.
(b) It is insoluble in water and turns blue litmus to red.
(c) It is soluble in water and turns red litmus to blue.
(d) It smells like vinegar and turns blue litmus to red.

Answer

D

Question. A student wants to prepare soap in the laboratory.
Which of the following sets of materials he should use ?
(a) Neem oil and NaCl
(b) Neem oil and Na2CO3
(c) Mustard oil and NaOH
(d) Mineral oil and NaOH

Answer

C

Question. The hetero-atoms present in
CH3 — CH2 — O — CH2 —CH2Cl is :
(i) Oxygen (ii) Carbon
(iii) Hydrogen (iv) Chlorine
(a) (i) and (ii) (b) (ii) and (iii)
(c) (iii) and (iv) (d) (i) and (iv)

Answer

D

Question. The chemical mostly used in the preparation of most of the soaps we use is :
(a) Sodium chloride
(b) Potassium hydroxide
(c) Sodium hydroxide
(d) Potassium chloride

Answer

C

Question. The first member of alkyne homologous series is :
(a) Ethyne
(b) Ethene
(c) Propyne
(d) Methane

Answer

A

Question. Which of the following does not belong to the same homologous series ?
(a) CH2
(b) C2H6
(c) C3H8
(d) C4H8

Answer

D

Question. A student is testing water to know which is best for cleansing purposes with soaps. He would find that the cleansing action of soaps is best when he uses water obtained from :
(a) rain
(b) tap
(c) hand pump
(d) pond

Answer

A

Question. The bond between two identical non-metallic atom has a pair of electron :
(a) unequally shared between two atoms.
(b) transferred completely from one atom to another.
(c) with identical spins.
(d) equally shared between them.

Answer

D

Carbon and Its Compound Class 10 Science Exam Questions

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