CBSE Class 10 Science Carbon And Its Compounds Worksheet Set F

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

Question. How many structural isomers can you draw for pentane?
Answer : Three structural isomers can be drawn from pentane.
Pentane : _C5H12

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

Question. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

Answer : Carbon form large number of compounds due to the following properties:
(a) Catenation → Carbon shows the property of catenation that is the ability to form bonds with other carbon atoms forming long chains both branched and unbranched chains, and even rings.
(b) Tetravalency → Carbon has valency 4, it is capable of bonding with 4 other carbon atoms or atoms of other non-covalent elements, giving rise to compounds with specific properties depending on the elements present in the compound.
(c) Isomerism → Carbon compounds show the property of isomerism that is compounds having same molecular formula but different structural formula.

Question. How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer : (a) Acid test: Reaction with carbonates/hydrogen carbonates.
Take samples of alcohol and carboxylic acid in 2 test tubes, and add sodium carbonate or sodium bicarbonate solution to each. The compound which will produce brisk effervescence of CO₂ gas will be acid.
(b) Alcohol test: Take small amount of ethanol and ethanoic acid in test tube A and B. Add 5% solution of alkaline potassium permanganate drop by drop to this solution and warm the test tube.
The colour of potassium permanganate will disappear in test tube containing alcohol.

Question. Would you be able to check if water is hard by using detergent?
Answer : No, because detergent forms lather in both, hard and soft water.

Question. Ethane, with the molecular formula C2H6 has
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.
Answer : (b) 7 covalent bonds.

Question. Butanone is a four-carbon compound with the functional group
(a) carboxylic acid.
(b) aldehyde.
(c) ketone.
(d) alcohol.
Answer : (d) ketone.

VERY SHORT ANSWER TYPE QUESTIONS 

Question. Name two allotropes of carbon.
Answer : Two allotropes are – Crystalline and amorphous
Crystalline form – Diamond and graphite.
Amorphous form – Charcoal, coal, coke.

Question. Why covalent compounds have low melting and boiling points?
Answer : As the bond is formed by sharing of electrons between two atoms. Intermolecular forces are small between the covalent compounds. These bonds break easily.

Question. What is an homologous series? Explain with an example.
Answer : It is a group of members of same class of organic compound having similar chemical properties, they have same general formula.
They have same functional group, when arranged in the ascending order of molecular mass they differ by 14 a.m.u. or —CH₂ group.

Question. What is a hydrocarbon?
Answer : It is a compound of hydrogen and carbon.

Question. Define oxidising agents.
Answer : Some substances are capable of adding oxygen to others. These substances are known as oxidising agents.
Example: alkaline KMnO4 and acidified K₂Cr₂O₇.

Question. Define catalyst.
Answer : Catalyst are substances that cause a reaction with a change in rate of reaction, without itself undergoing any change.
Example: Micelle acts as a catalyst to convert unsaturated hydrocarbon into saturated hydrocarbon.

Question. Give different forms in which carbon occurs in nature.
Answer : Carbon occurs in free form e.g., graphite and diamond in combined form like carbon dioxide, carbonates, etc.
In earth’s crust–0.02% and in atmosphere–0.03%.

Question. Give two properties of ethanol.
Answer : (a) Liquid at room temperature
(b) Soluble in H₂O in all proportions

Question. Give the full form of IUPAC.
Answer : IUPAC → International Union of Pure and Applied Chemistry.

Question. Give the IUPAC name and write the functional group present in vinegar.
Answer : Vinegar IUPAC name is acetic acid CH₃COOH
Functional group –COOH

Question. How can esters be converted into soap?
Answer : By saponification reaction, by adding/reacting ester with NaOH.

Question. What are heteroatoms?
Answer : An element or group of elements which replaces one or more hydrogen (H) atoms from hydrocarbon, such that valency of carbon remains satisfied.
Example: CH₄ ⎯→ CH₃ – OH
Hence, —OH is a heteroatom.

Question. What are covalent bonds?
Answer : Bond which are formed by sharing of a pair of electrons between two atoms is called covalent bonds.

Question. Name two types of hydrocarbon.
Answer : Hydrocarbon – Saturated and unsaturated.

SHORT ANSWER TYPE QUESTIONS 

Question. How does ethanoic acid react with carbonates and hydrogen carbonates? Show it with the equation.
Answer : Ethanoic acid reacts with carbonates and hydrocarbonates to form salt, CO₂ and H₂O.
The salt formed is sodium acetate.
2CH₃COOH + Na₂CO₃ ⎯→ 2CH₃COONa + H₂O + CO₂
CH₃COOH + NaHCO₃ ⎯→ CH₃COONa + H₂O + CO₂

Question. Diamond and graphite show different physical properties although they are made up of carbon and shows same chemical properties. What is this property called?
Answer : This property is allotropy.
The physical properties are different because the carbon-carbon bonding in both the cases varies. In diamond one carbon atom is bonded with four other carbon atoms with strong covalent bond so it is hard, while in case of graphite each carbon forms two strong bonds with other two carbon atoms and one weak bond is formed with third carbon atom and forms hexagonal rings which slide over each other, so it is soft.

Question. Write the general formula for each of the following hydrocarbons and give one example for each.
(i) Alkene (ii) Alkyne
Answer : (i) Alkene CnH₂n e.g., C₂H₄ ethene
(ii) Alkyne CnH₂n–2 e.g., C2H₂ ethyne

Question. What is esterification and give its uses?
Answer : It is the reaction in which esters are formed by reacting carboxylic acid with alcohol in the presence of concentrated sulphuric acid.
Carboxylic acid + alcohol ⎯⎯→ Ester + water
C₂H₅OH + CH₃COOH ⎯⎯→ CH₃COOC₂H₅ + H₂O
Ethanol Ethanoic acid Ester
Uses:(i) It is used as flavour in ice-cream and sweets.
(ii) It is a sweet smelling substance.

Question. What is the reactive site in the given hydrocarbon? Write its name.
H3C—CH₂—CH==CH—CH₃
Answer : The reactive site is at a place where double bond is present.
Name of the compound is 2-pentene.

Question. What is the difference in the number of carbon and hydrogen atoms between two successive members of a homologous series? Also give the difference in their atomic masses.
Answer : The difference is of 1 carbon and two hydrogen atoms i.e., —CH₂ and mass difference is 14 a.m.u.

Question. What is denatured alcohol?
Answer : When ethanol is mixed with methanol or some poisonous substances such as copper sulphate, pyridine which makes it unfit for drinking such alcohol is called denatured alcohol.

Question. Explain substitution reaction with example.
Answer : The reaction of saturated hydrocarbon with chlorine in which each hydrogen atom slowly gets substituted with chlorine atom is called substitution reaction.
CH₄ + Cl₂ ⎯⎯→ CH₃Cl + HCl
Methane Chlorine Methyl Hydrochloric

Question. Why acetic acid is called glacial acetic acid?
Answer : Acetic acid has very low melting point i.e. 290 K, hence it freezes during winters in cold countries. So it is called glacial acetic acid.

LONG ANSWER TYPE QUESTIONS

Question. Identify the compound A, B, C, D, and E in the following reaction:
(a) CH3CH2OH → Ⓐ CH3COOH
(b) CH₃CH₂OH + CH₃COOH → conc. Ⓑ + H2O H2SO4
(c) B + NaOH → C2H₅OH + Ⓒ
(d) D + Na₂CO₃ → CH3COONa + E + H₂O
(e) E + Ca(OH)2 → Ⓕ + H₂O
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Answer : (a) A = Alkaline KMnO₄ or acidified K₂Cr₂O₇
(b) B = CH₃COOC₂H₅
(c) C = CH₃COONa
(d) D = CH₃COOH; E = CO₂
(e) E = CO₂; F = CaCO₃

Question. Write an activity to show the acidic nature of ethanol. Give the chemical equation of the reaction taking place.
Answer : Take ethanol in a test tube and drop a small piece of sodium about the size of a grain of rice into it. The reaction evolves a colourless gas which is hydrogen.
Hydrogen gas can be tested by bringing a burning splinter/match stick near the mouth of the test tube, it burns with the popping sound.
This activity proves that ethanol like other acids release H2 gas
2Na + 2CH₃CH₂OH ⎯⎯→ 2CH₃CH₂ONa + H₂

Question. A compound ‘X’ has molecular formula C2H6O is saturated hydrocarbons and is a very good solvent. How can you convert it into unsaturated hydrocarbon? Identify X and show its conversion with the help of equation.
Answer : ‘X’ is CH₃—CH₂OH ethanol. It can be made unsaturated by heating it with conc.
H₂SO₄ which is a dehydrating agent removes water from it, thereby forming ethene.

Question. A hydrocarbon compound A is active ingredient of wine and cough syrup. A on oxidation with acidified K₂Cr₂O₇ forms compound B. Identify the compound A and B and write the chemical equations involved.
Answer : A is ethanol, C₂H₅OH
B is ethanoic acid, CH₃COOH
Equation : C₂H₅OH acid K₂Cr₂O₇ ⎯⎯⎯⎯⎯⎯→ CH₃COOH

Question. An organic compound ‘A’ is widely used as a preservative in pickles and has a molecular formula C₂H₄O₂. This compound reacts with ethanol to form a sweet smelling compound ‘B’.
(a) Identify the compound ‘A’.
(b) Write the chemical equation for its reaction with ethanol to form compound ‘B’.
(c) How can we get compound ‘A’ and ‘B’?
(d) Which gas is obtained when compound ‘A’ reacts with washing soda? Give the equation.
(e) Write an equation to obtain ‘A’ back from ‘B’.
Answer : (a) ‘A’ is CH₃COOH acetic acid.
(b) CH₃COOH + C₂H₅OH ⎯⎯→ CH₃COOC₂H₅ + H₂O
(c) We can get compound A back by the process of saponification.
(d) A + washing soda ⎯⎯→ CO₂ gas is produced
2CH₃COOH + Na₂CO₃ ⎯⎯→ 2CH₃COONa + H₂O + CO₂
(e) Saponification
CH₃COOC₂H₅ ⎯N⎯aO⎯H→ C₂H₅OH + CH₃COONa

Question. A, B, C are members of homologous series their melting points are –183°C, –138°C, 130°C respectively. Among these
(i) Which member will have least number of carbon atoms?
(ii) Which member will have maximum number of carbon atoms?
Answer : (i) A will have least number of carbon atoms.
(ii) C will have maximum number of carbon atoms.