CBSE Class 10 Science Carbon and its compounds Assignment Set B

Very Short Answers

Question : Draw electron dot structure of carbon dioxide and write the nature of bonding between carbon and oxygen in its molecule. 
Answer :
 ..         ..
:O: :C: :O    : or O = C = C
 ..        ..
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 : 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 C^4– 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 : 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 : 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 (a) Methane and (b) Ethanol.
Answer :
(a) CH₄ (b) C₂H₅OH or C₂H₆O

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 molecular formula of (a) ethane and (b) ethanoic acid 
Answer :
(a) C₂H₆
(b) CH₃COOH

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

Short Answers

Long Answers

Assertion and Reasoning Based Questions

Directions : In the following questions, a statement of assertion is followed by a statement of reason. Mark the correct choice as :
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If assertion is false but reason is true.

Question. Assertion : Carbon and its compounds are used as fuels.
Reason : They give lot of heat and light when burnt in air.
Answer : (a) 

Question. Assertion : Detergents are better cleansing agent than soaps.
Reason : It is because they work with soft water.
Answer : (c) 

Question. Assertion : General formula of alkanes is CnH2n + 2.
Reason : It is because they are saturated compounds.
Answer : (b) 

Question. Assertion : Hard water contains magnesium and phosphate salts.
Reason : It is because they are easily available in water.
Answer : (d) 

Question. Assertion : Ethane is the homologous of methane.
Reason : It is because it differs by CH₃ group.
Answer : (b) 

Creating Based Questions

Question. Covalent bonds formed as a result of sharing of electron pairs between two atoms are strong in nature. But the covalently bonded molecules have low melting and boiling points compared to the ionic molecules. What is the reason behind such behaviour ?
Answer : Covalent bond is formed by equal sharing of valence electrons between two atoms, hence there is no charge separation along the bond formed and they have weak intermolecular forces. Due to this, covalently bonded molecules have low melting and boiling points.

Question. Why are the unsaturated carbon compounds more reactive than saturated carbon compounds?
Answer : Unsaturated carbon compounds have double or triple bonds between carbon atoms, which are less stable than the sigma bonds and hence more reactive than saturated compounds which have single bond.

Question. Which property of ethanol enables its use in preparation of certain types of medicines ?
Answer :  Ethanol is a very efficient solvent hence, it is used as a base for many medicines which are prepared in suspension or solution form.

Question. A shiny soft metal is put in a test tube containing ethanol, a reaction takes place within the test tube with evolution of bubbles. The gas is collected and exposed to a burning candle. The gas burns with a pop sound.
(i) Name the shiny soft metal.
(ii) Name the gas evolved as a result of chemical reaction.
(iii) Write the equation for chemical reaction.
Answer : 
(i) The shiny soft metal is sodium.
(ii) Hydrogen gas is evolved as a result of the reaction between sodium metal and ethyl alcohol. The presence of hydrogen gas can be tested by bringing a burning candle near a gas filled bubble, hydrogen gas burns with a pop sound.
(iii) The reaction equation can be given as :
2Na(s) + 2C₂H₅OH(l)   →   2C₂H₅ONa + H₂(g)

Question : Question.Give a chemical test to distinguish between ethanol and ethanoic acid.
Answer : Ethanoic acid is a two-carbon containing compound with a carboxylic acid functional group. Addition of sodium hydrogen carbonate solution to the ethanoic acid leads to evolution of bubbles from the reaction mixture. The gas evolved is carbon dioxide. Whereas, addition of sodium hydrogen carbonate solution to ethanol does not give any bubbles.

Question : Question. What is the product formed when a hydrocarbon is oxidised completely in presence of oxygen ?
What is the name of reaction ?
Answer : A hydrocarbon is oxidised completely to give carbon dioxide and water along with heat and light. The reaction is known as combustion.

Question. Why do the burners of gas or kerosene stoves contain small holes ?
Answer : The small holes present in burners of gas or kerosene stoves are actually small inlets for air to allow sufficient oxygen rich air mixture which ends up in giving clean blue flame.

Case study question

1. Water is a simple molecule consisting of one oxygen atom bonded to two different hydrogen atoms. Because of the higher electronegativity of the oxygen atom, the bonds are polar covalent (polar bonds). The oxygen atom attracts the shared electrons of the covalent bonds to a significantly greater extent than the hydrogen atoms. The molecule has a bent structure, the H—O—H bond angle is about 105°.

Question : What is the shape of water molecule?
(a) Linear
(b) Trigonal planar
(c) Bent
(d) Octahedral

Answer : C

Question : The correct electron dot structure of a water molecule is
(a) H O O
(b) H O O
(c) H O H
(d) H O O

Answer : C

Question : Which of the following statement is true regarding the electronegativity of atoms in water molecule?
(a) Hydrogen is more electronegative than oxygen
(b) Hydrogen is less electronegative than oxygen
(c) Electronegativity is same in Hydrogen and oxygen
(d) Hydrogen and oxygen do no show significant electronegativity in water

Answer : B

Question : The H—O—H bond angle in water molecule is
(a) 109.5°
(b) 180°
(c) 90°
(d) 105.0°

Answer : D

Question : Select the correct type of bonding in a water molecule
(a) Ionic Bonding
(b) Covalent Bonding
(c) Hydrogen Bonding
(d) None of these

Answer : B

Question : What is homologous series?
Answer : It is a series of organic compounds having same functional group and similar chemical properties

Question : The molecular formula of two members of a homologous series are C₃H₄ and C₆H₁₀. Write the molecular formula of a member of this family with five carbon atoms in a molecule.
Answer : C₅H₈

Question : An alkene ‘P’ has three carbon atoms and an alcohol ‘Q’ has four carbon atoms. Write the formulae of P and Q.
Answer : ‘P’ is CH₃–CH=CH₂, ‘Q’ is CH₃CH₂CH₂CH₂OH

Question : Write the general formula of alkenes. Write the name of the simplest alkene.
Answer : CnH₂n, Ethene is simplest alkene

Question : Write the next homologue of each of the following: (i) C₂H₄, (ii) C₄H₆
Answer : (i) C₃H₆, (ii) C₅H₈

Question : Write the molecular formula of benzene and state the number of double bonds in its structure.
Answer : C6H6, It has three double bonds

Short Answers

Question. What happens when (write chemical equation in eachcase) 
(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
                        Conc H₂SO₄
(b) CH₃CH₂OH       →                CH₂ = CH₂ + H₂O 
                          Δ 443k 
(c) 2CH₃CH₂OH + 2Na → 2CH₃CH₃ONa + H₂↑

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. 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.
CH₃CH₂CH = CH₂ + H₂  Pd/Ni→   CH₃CH₂CH₂CH₃
CH₃CH = CHCH₃ + Cl₂     hv→     CH₃ClCHClCHCH₃

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.
CH₃ — CH = CH₂ + Cl₂   →  CH₃CH — CH₂Cl
                                            |
                                           Cl

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. 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. (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. (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 C_nH_2n+2.
Answer :
(a) Alkynes, C_nH_2n–2
First member : Ethyne : C₂H₂
(b) Second member : C₃H₆
Fifth member : C₅H₁₂
(c) Third member : C₃H₈
Fourth member : C₄H₁₀

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. 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. Give reasons :
(a) Why is pure ethanoic acid known as glacial aceticacid ?
(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 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. 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. 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
(b) CH₃COOH + C₂H₅OH       →           CH₃COOC₂H₅          
                                         −H₂O
Conc. H₂SO₄ acts as a catalyst or dehydrating agent.
(c) Used in perfume industry and as flavouring agent.

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 C_nH_{2n + 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. Give reason why carbon can neither form C⁴⁺ cations nor C^4– 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 C^4- 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. 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.
CH₃CH₂OH        Acidified K₂Cr₂O₇→     CH₃COOH
2CH₃COOH + 2Na → 2CH₃COONa + H₂

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. (a) What is a homologous series ? Explain with an example.
(b) State two characteristics of a homologous series.
(c) The molecular formula of an organic compound is C₁₈H₃₆. Name its homologous series.
(d) Select the hydrocarbons which belong to the same homologous series. Give the name of each series. CH₄, C₂H₂, C₂H₄, C₂H₆, C₄H₁₀, C₃H₄, C₃H₆
(e) What is meant by ‘heteroatom’ ? Give examples. Write the names and formulae of two organic compounds containing different heteroatoms.
Answer :
(a) A homologous series is a group of organic compounds having similar structures and similar chemical properties in which the successive compounds differ by CH₂ group. Example of homologous series : All the alkanes have similar structures with single covalent bonds and show similar chemical properties, so they can be grouped together in the form of a homologous series. Homologous series of alkanes : Methane, CH₄; Ethane, C₂H₆; Propane, C₃H₈; Butane, C₄H₁₀; Pentane, C₅H₁₂.
(b) (i) All the members of the homologous series can be represented by the same general formula.
(ii) Any two adjacent homologues differ by 1 carbon atom and 2 hydrogen atoms in their molecular formulae.
(c) Alkene, C_nH_2n
(d) Alkanes: CH₄; C₂H₆ ; C₄H₁₀
Alkenes : C₂H₄, C₃H₆
Alkynes : C₂H₂, C₃H₄
(e) In an organic compound, any atom other than carbon and hydrogen is called a heteroatom.
Example : Chlorine (Cl), Bromine (Br), Oxygen (O)
Chloromethane – CH₃Cl and methanol –CH₃OH.

Question. Explain the given reactions with the examples :
(a) Hydrogenation reaction
(b) Oxidation reaction
(c) Substitution reaction
(d) Saponification reaction
(e) Combustion reaction
Answer :
(a) Unsaturated hydrocarbons add hydrogen in the presence of nickel catalyst to give saturated hydrocarbons.
R₂C = CR₂ + H₂    Ni→    R₂C — CR₄
                                          |      |
                                          H     H
(b) Ethanol is oxidised to ethanoic acid in the presence of alkaline KMnO₄ on heating.
                     Alc. KMnO₄
CH₃CH₂OH      Hert →       CH₃COOH
(c) In the presence of sunlight, chlorine is added to hydrocarbons.
CH₄ + Cl₂    hv→    CH₃Cl + HCl
(d) CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH Ester Used in the preparation of soap.
(e) Most carbon compounds release a large amount of heat and light on burning
CH₄ + 2O₂  → 2H₂O + Heat and light

Question. (a) Write a chemical test to distinguish between saturated and unsaturated hydrocarbons.
(b) Name the products formed when ethane burns in air. Write chemical equation for the reaction showing various types of energies liberated.
(c) Write the reaction between methane and chlorine in the presence of sunlight. Why is this reaction considered a substitution reaction ?
Answer :
(a) Bromine water test is used to differentiate between the unsaturated compounds (like alkanes and alkynes) and the saturated compounds. For this purpose, bromine is used in the form of bromine water. Bromine water has a red-brown colour due to the presence of bromine in water. When bromine water is added to an unsaturated compound, then bromine gets added to the unsaturated compound and the red-brown colour of bromine water is discharged. So, if an organic compound decolourises bromine water, then it will be an unsaturated hydrocarbon (containing a double bond or a triple bond,) but saturated hydrocarbon (alkenes) do not decolourise bromine water.
(b) Carbon dioxide (CO₂) and Water (H₂O)
2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O + Heat + Light
(c) CH₄ + Cl₂   sunlight→ CH₃Cl + HCl ; This reaction is considered a substitution because hydrogen atom is replaced by chlorine atom.

Question. What are esters ? How are esters prepared ? Write the chemical equation for the reaction involved. What happens when an ester reacts with sodium hydroxide ?
Write the chemical equation for the reaction and also state the name and use of this reaction. 
Answer :
Esters : They are sweet-smelling organic compounds,with the general formula RCOOR’ (R and R’ are similar or dissimilar alkyl groups)
Preparation of ester : Esters are prepared by esterification which is a reaction between carboxylic acids and alcohols in the presence of an acid.
For example, when ethanoic acid reacts with ethanol in the presence of an acid, ethyl ethanoate is formed. Ethyl ethanoate is an ester, and has a sweet smell.
CH₃CH₂OH   +   CH₃COOH     Acid →   CH₃COOCH₂CH₃            + H₂O
Ehanol             Ethanoic acid                Ethyl ethanoate (Ester)     Water
Reaction with sodium hydroxide :
Ethyl acetate (an ester) reacts with sodium hydroxide (base) to form ethanol (alcohol) and ethanoic acid (carboxylic acid.)
CH₃COOCH₂CH₃   NaOH→    CH₃CH₂OH + CH₃COOH
Ethyl ethanoate                     Ethanol         Ethanoic acid
( Ester)
Thus, alcohol and carboxylic acid can be reclaimed from an ester by reacting it with an acid or a base. This reaction is used in the preparation of soaps and it is known as saponification reaction.

Question. What are micelles ? Why does it form when soap is added to water ? Will a micelle be formed in other solvents such as ethanol also ? State briefly how the formation of micelles help to clean the clothes having oily spots.
Answer :
Soap molecules have two ends – at one end is the hydrocarbon chain which is water repellent, whereas at the other end there is the ionic part which is water soluble end. When soap is dissolved in water it forms a group of many molecules, known as micelle. These micelles are formed because their hydrocarbon chains `come together and the polar ends are projected outwards. Micelle formation in ethanol will not occur because the hydrocarbon chain end of the soap will dissolve in ethanol. Soaps in the form of micelle are able to clean dirty clothes having oily spots, as the oily dirt is collected in the centre of the micelle, which forms an emulsion in water and on rinsing, the water washes away the micelles with dirt attached to them