CBSE Class 10 Science Carbon and its compounds Assignment Set G

Very Short Answer Type Question

Question. Name the given compound

Answer: 2-Butanone.

Question. Name the compound

Answer: Benzene, C6H6.

Question. How can you convert ethene into ethane?
Answer: By adding hydrogen to ethene in the presence of a catalyst.

Question. Why can’t we test hard water with detergents?
Answer: Detergents form lather with both hard and soft water hence we cannot distinguish between them.

Question. What is esterification reaction?
Answer: The reaction in which alcohol reacts with carboxylic acid to produce a new compound called ester is called esterification.

Question. (a) Name the compound CH3CH2OH and identify its functional group.
(b) Give a chemical test to distinguish between ethanol and ethanoic acid.
(c) Name the product formed when an organic acid reacts with an alcohol in presence of an acid catalyst. What is the name assigned to this type of reaction? (AI CBSE 2008 C)
Answer: (a) CH₃CH₂OH – Ethanol
Functional group: alcohol (–OH)

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

Question. Write the name and formula of the second member of the carbon compounds having functional group —OH.
Answer: 

Question. Explain the nature of the covalent bond using the bond formation in CH₃Cl.
Answer: Bond formation in CH₃Cl

Short Answer Type Question

Question. Differentiate between ethanol and ethanoic acid on basis of the following test:
(i) Blue litmus test (ii) Reaction with sodium bicarbonate (iii) Sodium metal test
Answer: 

 Question. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Answer: Soap molecules have two ends with different properties. One end is hydrophilic, which dissolves in water and other end is hydrophobic, it dissolves in hydrocarbons. When soap is added to water, the ionic end of soap will form a unique orientation and keep the hydrocarbon tail away from it.
The cluster of molecules is formed in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. Hence, micelle formation takes place.
Soap is soluble in ethanol hence the micelle formation will not take place.

Question. What is hydrogenation? What is its industrial application?
Answer: When unsaturated hydrocarbons (double/triple bond) are reacted with hydrogen in presence of a catalyst like nickel, the hydrogen gets added across the double/triple bond and converts the unsaturated hydrocarbon into saturated hydrocarbon. Such reaction is called addition reaction or hydrogenation.

Question. Give a test that can be used to differentiate chemically between butter and cooking oil.
Answer: Butter is saturated compound and oil is unsaturated compound.
Test alk. potassium permanganate + Unsaturated → Pink colour disappear.
(Pink colour) hydrocarbon
Therefore, when we add oil to a test tube containing alkaline potassium permanganate solution, the pink colour of the solution disappear. Colour of alkaline potassium permanganate will not disappear in the test tube containing butter.

Question. Explain the mechanism of cleaning action of soaps.
Answer: Soap molecule has two ends, the charged end that gets attracted towards water is called hydrophilic and the long carbon chain that repels water is called hydrophobic end. When soap is dissolved in water, the carbon chain i.e., hydrophobic end gets attracted towards the oil, dirt and grease. The hydrophilic end stays away from this.
The micelle formation takes place.
The tail entangles dirt, oil or grease, if required the agitation is done. Lot of rinsing is a done with water so that water molecules attract charged (Na+) end and carries the soap molecules with dirt attached to it and clean the clothes, utensils, etc.

Question. Why are certain compounds called hydrocarbons?
Write the general formula for homologous series of alkanes, alkenes and alkynes and also draw the structure of the first member of each series. Write the name of the reaction which converts alkene into alkane. Also write the chemical equation to show the necessary conditions for the reaction to occur.
Answer: Compounds of carbon and hydrogen are called hydrocarbons.
Alkane CnH₂n⁺² 

Question. a. Give a chemical test to distinguish between saturated and unsaturated hydrocarbons.
b. Name the products formed when ethane burns in air. Write the balanced chemical equation for the reactions showing two types of energies liberated.
c. Why is reaction between methane and chlorine in presence of sunlight is considered a substitution reaction.
Answer: a. Saturated hydrocarbons will not react with bromine water whereas unsaturated hydrocarbons will decolourise it.
b. Carbon dioxide and water will be formed.
2C₂H₆ + 7O₂ → 4CO₂(g) + 6H₂O(l)
                        + Heat   +  Light
c. It is because hydrogen atom is substituted by halogen atom, that is why it is called substitution reaction.

Question. a. You have three unlabelled test tubes containing ethanol, ethanoic acid and soap solution. Explain the method you would use to identify the compounds in different test tubes by chemical tests using litmus paper and sodium metal.
b. Give reason of formation of scum when soaps are used with hard water.
Answer: a. Red litmus paper will become blue in soap solution only. Ethanoic acid will turn blue litmus red only. Ethanol will react with Na metal to form sodium nethoxide and hydrogen gas will be liberated.
b. Soaps are sodium or potassium salts of fatty acids which react with Ca2+ and Mg2+ ions in hard water to form calcium or magnesium salts of fatty acids which are insoluble in water called scum.

Question. What are micelles? Why does it form when soap is added to water? Will a micelle be formed in other msolvents such as ethanol also? State briefly how the nformation of micelles help to clean the clothes having oily spots.
Answer: Micelles are cluster of molecules in which hydrophobic tails are inside the cluster 3 and the ionic ends are at the surface of clusters. Soap molecules when dissolved in water they form a cluster due to hydrophobic part of molecules orient themselves away from water.
So they arrange towards inside of the cluster while hydrophilic part remain outside of cluster.
No, micelles will not be formed in alcohol. Soap in form of micelles is able to clean because the oily dirt will be collected in centre of micelle which is rinsed away by water.

Question. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing, even in the case of water having calcium and magnesium ions.
Answer: Detergents chemically are sodium or potassium salts of sulphonic acid of benzene or alkene.
Merits:
(i) They work well with hard water.
(ii) They are more effective than soaps.
Demerits:
(i) They are expensive.
(ii) Some of them having branching are non-biodegradable, therefore create water pollution.
Detergents are suitable for hard water having Mg₂⁺ and Ca₂⁺ ions because they do not form insoluble salts with Mg₂⁺ and Ca₂⁺ ions.

Question. An organic compound “X’ on heating with cone. 
H₂SO₄ forms a compound ‘Y’ which on addition of one molecule of hydrogen in the presence of nickel forms a compound ‘Z’. One molecule of compound ‘Z’ on combustion forms two molecules of CO2 and three molecules of H₂O. Identify giving reasons the compounds X’, ‘Y’ and ‘Z’. Write the chemical equations for all the chemical reactions involved.
Answer: 

C₂H₆ + (7/2)O₂ → 2CO₂ + 3H₂O
‘Z’ on combustion gives 2CO₂ and 3H₂O so hydrocarbon ‘Z’ must be ethane. “Y’ on addition of H₂ gives ethane so ‘Y’ must be ethene. “X’ in presence of cone. H₂SO₄ dehydrates to ethene i.e., ‘X’ is ethanol.

Question. What are detergents chemically? List two merits and two demerits of using detergents for cleansing. State the reason for the suitability of detergents for washing even in case of water having calcium and magnesium ions.
Answer: Detergents are sodium or potassium salts of sulphonic acids of benzene or sulphates of unsaturated hydrocarbons like alkenes with —SO₃Na or —SO₄Na group.
Merits:
They are more effective than soaps.
They work well even with hard water.
Demerits:
a. They are expensive.
b. Some of them create water pollution.

Question. Give reasons for the following:
a. Element carbon forms compound mainly by covalent bonding.
b. Diamond has high melting point.
c. Graphite is good conductor of electricity.
d. Acetylene bums with sooty flame.
e. Kerosene does not decolourise bromine water whereas cooking oil does.
Answer: a. It is because carbon can neither lose 4 electrons nor gain 4 electrons. It can share four electrons to form covalent bonds.
b. Diamond has strong C—C bonds and compact 3-D structure in which one carbon atom is covalently bonded to other four carbon atoms therefore, has high melting point.
c. In graphite, one carbon atom is bonded to other three carbon atoms. Remaining one electron on each carbon is free to move due to which graphite conducts electricity.
d. Acetylene has high carbon content, therefore, partial oxidation causes it to bum with sooty or smoky flame.
e. Kerosene is a saturated compound, therefore, does not decolourise bromine water.

Question. a. Differentiate between soap and detergent.
b. Explain why, soaps form scum with water whereas detergent do not.
Answer: 

b. Sodium salts of fatty acids (soaps) react with Ca2+ and Mg2+ ions in hard water to form insoluble salts called scum. Detergents form soluble salts with Ca2+ and Mg2+.

Question. a. How is vinegar made?
b. What is glacial acetic acid? What is its melting point?
c. Why are carboxylic acids called weak acids?
d. Write the name and formula of compounds formed when the ester CH₃COOC₂H₅ undergoes saponification.
Answer: a. Vinegar is 5-8% solution of acetic acid (Ethanoic acid) in water. It can be made by fermentation of ethanol in presence of oxygen.
b. Glacial acetic is pure (100%) acetic acid. Its melting point is 290 K.
c. They do not ionise completely in aqueous solution.
d. CH₃COOC₂H₅ + NaOH → CH₃COONa + C₂H₅OH
                                        Sodium ethanoate Ethanol

Question. Suman always carried her tiffin box in a jute bag while most of her friends got it packed in a poly bag.
(a) What type of bonding is present in polythene?
(b) Give one advantage of carrying jute and disadvantage of poly bag.
(c) Which value is reflected in Suman by using jute bag?
Answer: (a) In polythene, long chain of ethene is present – C = C –.
(b) Jute bag is biodegradable and will not cause pollution. While poly bag is nonbiodegradable and causes pollution.
(c) Suman shows the value of a responsible behaviour.

Question. Geeta helps her mother in washing clothes, toilets, balconies every Sunday. She uses thele ftover detergent water of washing machine to clean toilets.
(a) Why is detergent used in washing clothes?
(b) Give one advantage of detergent over soap.
(c) What value of Geeta is reflected in the above task?
Answer: (a) Detergents have strong cleansing ability and can remove oil and dirt from clothes or other surfaces.
(b) Soap cannot be used in hard water but detergents can be used in hard water.
(c) Geeta is trying to reduce water pollution and water shortage problem. She also shows helpful to her mother and responsible behaviour.

Question. Giving chemical equations of the reactions write what happens when
(i) Ethanol is heated with excess of concentrated sulphuric acid at 443 K.
(ii) Ethanoic acid reacts with ethanol in presence of an acid.
(iii) Ester with molecular formula CH₃COOC₂H₅ reacts with sodium hydroxide.
Answer: 

Question. Name the functional group of organic compounds that can be hydrogenated. With the help of suitable example explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.
Answer: 

When unsaturated hydrocarbons are heated with hydrogen in the presence of nickel as catalyst, saturated hydrocarbons are formed. If the starting unsaturated hydrocarbons are liquids, they will change into solids. Vegetable oils are hydrogenated to form vegetable ghee. Plants are natural sources of vegetable oils which can be hydrogenated.

Long Short Answer Type Question

Question. (a) Why does carbon form compounds mainly by covalent bonding?
(b) List any two reasons for carbon forming a very large number of compounds.
(c) 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: (a) Carbon forms compounds mainly by covalent bonding because carbon has small size, so neither it can loose four electrons easily, because very high amount of energy will be required, nor it can gain four electrons. Hence, it shares four electrons forming covalent bonds.
(b) (i) Due to catenation – Self linking property
(ii) Tetravalency of carbon – Forms compounds with other elements.
(c) (i) ‘X’ is CH3COOH, it freezes during winter in cold countries.
‘Y’ is ester CH₃COOC₂H₅
(ii) CH₃COOH + C₂H5OH ⎯C⎯onc⎯. H₂SO₄→ CH3COOC₂H₅ + H₂O
Ethanoic acid Ethanol Ester

Question. (a) What is homologous series of compounds? List any two characteristics of a homologous series.
(b) (i) What would be observed on adding 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.
(c) How would you distinguish experimentally between an alcohol and a carboxylic acid on the basis of a chemical property?
Answer: (a) Organic compounds when arranged in series having same general formula and similar chemical properties is called homologous series.
Two characteristics of homologous series.
(i) Each successive member differ by —CH2 group, 14 u.
(ii) The method of preparation and chemical properties of members of homologous series is same.
(b) (i) The colour of KMnO4 will get discharged because ethanol gets oxidised to form ethanoic acid.
CH₃CH₂OH + 2(O) ⎯a⎯lk. ⎯KMnO₄→ CH₃COOC₂H₅ + H₂O
(ii) Ethanoic acid
(c) On adding sodium bicarbonate solution to both the test tubes containing ethanol and ethanoic acid then the test tube containing carboxylic acid (ethanoic acid) will show brisk effervescence due to formation of CO₂ gas. Alcohol will not react with sodium bicarbonate.

Question. (a) What is a functional group in a carbon compound? Identify the functional group present in CH₃COOH and C₂H₅OH.
(b) State the principle on which the cleansing action of soap is based.
Answer: (a) The atom or group of atoms which determines the properties of a compound is called functional group.
— OH is alcohol group
— COOH is carboxylic group
(b) Cleansing action of soap depends on its structure, it has two ends hydrophobic which attracts dirt, oil or grease and hydrophilic end which attracts water.

The dirt is carried by hydrophobic portion which is attached to hydrophilic end which gets attached to water and is washed away.

Question. (a) Distinguish between esterification and saponification reactions of organic compounds.
(b) With a labelled diagram describe an activity to show the formation of an ester.
Answer: (a) Esterification: Reaction in which carboxylic acid reacts with alcohol in presence of conc. H2SO4 to form a fruity smelling compound called ester.
CH₃COOH + C₂H₅OH ⎯ ⎯Con⎯c. H⎯2S⎯O4⎯→CH₃COOC₂H₅ + H₂O
Saponification: It is a reaction in which an ester reacts with alkali solution to form a compound called soap.
CH₃COOC₂H₅ + NaOH ⎯⎯→ CH₃COONa + C₂H₅OH
Ester Sodium Sodium Ethanol
hydroxide ethanoate
(b) Activity to show the formation of an ester: Take a test tube and add ethanol, acetic acid and few drops of conc. H2SO4 in it. Warm it over a water bath, i.e., keeping the test tube in a beaker containing water. Pleasant, fruity smelling compound called ester is formed.
CH₃COOH + C₂H₅OH ⎯⎯Con⎯c. H⎯2S⎯O₄⎯→ CH₃COOC2H₅ + H₂O (Img 43)

Question. Explain isomerism. State any four characteristics of isomers. Draw the structures of possible isomers of butane, C₄H₁₀
Answer: Isomerism is a phenomenon due to which some compounds have same molecular formula but different structural formulae.
Characteristics:
(i) They differ in structural formula.
(ii) They differ in melting point.
(iii) They differ in boiling point.
(iv) They differ in solubility in same solvent.

Question. a. How will you bring out following reactions? Write the concerned chemical reaction.
(1) Ethanol to ethene
(2) Ethanol to ethanoic acid
b. Give one example with chemical equation for the following reactions:
(1) Substitution reaction
(2) Saponification reaction
(3) Combustion reaction
Answer: 

Question. Identify the compounds ‘A’ to ‘E’ in the following sequence: 

Answer: 

Question. a. In a tabular form, differentiate between ethanol and ethanoic acid under the following heads:
(i) Physical state
(ii) Taste
(iii) NaHCO3 test
(iv) Ester test
b. Write a chemical reaction to show dehydration of ethanol.
Answer: (i) 

Question. Soaps and detergents are both types of salts. State the difference between the two. Write the mechanism of the cleansing action of soaps. Why do soaps not form lather (foam) with hard water? Mention any two problems that arise due to the use of detergents instead of soaps.
Answer: a. Soaps are sodium or potassium salts of fatty acids e.g. —COONa. Detergents are sodium or potassium salts of sulphonic acids e.g. —SO3Na or —SO₄Na
b. Soaps are sodium or potassium salts of fatty acids. They contain —COONa group. Detergents are sodium or potassium salts of sulphonic acids.
They contains —SO₃Na or —SO4Na group. Soap has ionic end which is hydrophilic, interacts with water while carbon chain is hydrophobic interacts with oil, grease. The soap molecules orient themselves in a cluster in which hydrophobic tails are inside the cluster and ionic ends face outside.
These cluster are called micelles. These attract oil which is washed away by water.
c. Soaps react with Ca²⁺ and Mg²⁺ ions in hard water to form calcium or magnesium salts of fatty acids which are insoluble in water and thus interfere in action of soap,
d. (i) Detergents are more expensive than soaps.
(ii) Some detergents are not biodegradable i.e. will create pollution.