CBSE Class 10 Chemistry Carbon and Its Compounds Worksheet Set A

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

Question. While cooking, if the bottom of the vessel is getting blackened on the outside, it means that
(a) the food is not cooked completely.
(b) the fuel is not burning completely.
(c) the fuel is wet.
(d) the fuel is burning completely.
Answer : B

Question. The isomeric pair is
(a) ethane and propane
(b) propane and butane
(c) ethane and ethane
(d) butane and 2-methyl propane
Answer : D

Question. Which of the following is used to oxidise ethanol to ethanoic acid?
(a) Alkaline KMnO₄
(b) Conc. H₂SO₄
(c) Acidified K₂Cr₂O₇
(d) All of above
Answer : D

Question. Identify the product formed when methane reacts with chlorine in the presence of sunlight is
(a) C₂Cl₆
(b) CH₃Cl
(c) CHCl₄
(d) None of these
Answer : B

Question. Drinking alcohol and driving may cause serious accidents. To discourage this, police randomly test drivers for alcohol using a breath analyser. The breath analyser works because
(a) Alcohol makes the breath dry and the machine registers moisture
(b) Alcohol makes the breath hotter which changes the machine reading
(c) Alcohol causes more saliva which the machine checks.
(d) Alcohol in the breath cause a chemical change registered by the machine.
Answer : B

Question. The by product of soap is
(a) isoprene
(b) glycerol
(c) butene
(d) ethylene glycol
Answer : B

Question. The heteroatoms present is
CH₃ – O – CH₂ – CH₂ (Br)
(a) oxygen
(b) carbon
(c) hydrogen
(d) bromine
Answer : D

Question. Which of the following can be used for the denaturation of ethyl alcohol?
(a) Methyl alcohol
(b) Pyridines
(c) Copper sulphate
(d) All of above
Answer : D

Question. For gas welding used for welding broken pieces of iron, we normally use a mixture of
(a) Ethane and oxygen
(b) Ethene and oxygen
(c) Ethyne and oxygen
(d) Ethene and air
Answer : A

Quetion. What would be the product when a compound containing carbon is burnt?
Answer: CO₂

Quetion. What is the amount of carbon present in the earth's crust?
Answer: 0.02%

Quetion. What is the distribution of electrons in various shells of carbon?
Answer: 2+4

Quetion. Writethe number of covalent bonds in the molecule of ethane.
Answer: 7

Quetion. Covalent compounds are generally poor conductors of electricity. Why?
Answer: The electrons in covalent compounds are shared between atoms to form covalent compounds. They do not form any charged particles . Therefore, covalent compounds are poor conductor of electricity. Evaluation based

Quetion. Write the name and structure of an aldehyde with four carbon atoms in its molecule.
Answer: Butanal (draw structure)

Quetion. Write the name and molecular formula of the first members of the homologous series of alkynes.
Answer: Ethyne (C₂H₂), Propyne (C₃H₄), Butyne [1-Butyne and 2-Butyne] (C₄H₆).

Quetion. Priyanka went to Mussoorie with her parents. While washing her hands and face with soap, she noticed that scum was formed on her hands in place of lather. Why does this happen?
Answer: hard water. When soap is mixed with hard water it forms scum insted of lather.

Quetion. Adi's sister studies in class X and told him that the pencil is made up of carbon. He did not believe and asked his teacher. Which form of carbon is used to make lead of pencil and why?
Answer: lead of pencil is made of graphite. Graphite is an allotrope of carbon.

Quetion. We know that water is a universal solvent. When we try to dissolve ester in the water, it does not dissolve.
Why does ester not dissolving water?
Answer: Water is a ionic solvent which can dissolve polar substances which easily split into ions. Ether is an organic and non polar substance.

Quetion. Why are carbon and its compounds used as fuels for most applications?
Answer: Carbon compounds are used as fuel because they burn with a clean flame and no smoke is produced.Carbon compounds have higher calorific values, maximum ignition temperature and their combustion can be restrained. Hence, carbon and its compounds are a great source of fuel.

Quetion. What would be the electron dot structure of a molecule of sulphur which is made up of 8 atoms of sulphur?
Answer: The eight atoms of Sulphur are joined together in the form of a ring).

Quetion. What happens when 5% of alkaline potassium permanganate solution is added drop by drop to warm propyl alcohol taken from a test tube? Explain with the help of a chemical equation.
Answer: purple colour of potassium permanganate gradually disappears as it oxidizes the propanol to its respective carboxylic acid i.e propionic acid. Write chemical reaction)

Quetion. Why is the conversion of ethanol to ethanoic acid and oxidation reaction?
Answer: A molecule of ethanol contains six hydrogen atoms while that of ethanoic acid contains four hydrogen atoms since oxidation involves removal of hydrogen, therefore conversion of ethanol to ethanoic acid is an oxidation reaction.)

Quetion. Write the structural formula of any four isomers of hexane.
Answer:Write structural formula of C₆H₁₂

Question. Write the molecular formula of the 2nd and the 3rd member of the homologous series whose first member is methane. 
Answer : C₂H₆ and C₃H₈ are molecular formula of 2nd and 3rd member of alkanes.

Question. Write the general formula of hydrocarbon alkene. Write the name of simplest alkene. 
Answer : C_nH_2n, Ethene It has three double bonds.

Question. Why is diamond lustrous?
Answer : It is due to high refractive index.

Question. How much carbon is present on earth and CO₂ in atmosphere?
Answer : 0.02%, 0.03%

Question. What is valency of carbon?
Answer : 4

Question. Why carbon considered to be the most important element?
Answer : Carbon is considered to be the most important element because it forms largest number of compounds which are useful in our daily life.

Question. Name the following compounds: 
Answer : (a) Ethanol
(b) Ethanal

Question. Write the general formula of hydrocarbon alkene. Write the name of simplest alkene.
Answer : C_nH_2n, Ethene

Question. Carbon has four electrons in its valence shell. How does carbon attain stable electronic configuration.
Answer : By sharing four electrons with other atoms.

Question. Why does carbon form strong bonds?
Answer : It is due to small size.

Question. Name the first organic compound prepared in Laboratory.
Answer : In 1828, Wohlar prepared first organic compound urea by heating ammonium cyanate by isomerisation reaction.

Question. Why is carbon tetravalent? 
Answer : It is because carbon can share form electrons to complete its octet.

Question. Which element exhibits the property of catenation to maximum extent and why? 
Answer : Carbon shows catenation to maximum extent because it forms strong covalent bonds.

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

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

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

Question. What happens when ethanol burns in air?
Answer : Ethanol burns to form carbon dioxide and water.

Question. Give two uses of methane gas.
Answer : (i) It is used as a fuel (ii) It is the major component of biogas and CNG.

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

Question. Name the second member of alkyne series.
Answer : Propyne

Question. Give the IUPAC name of acetic acid and propyl alcohol.
Answer : Acetic acid – Ethanoic acid
Propyl alcohol – Propanol

Question. What is isomerism?
Answer : A property in which a compound can exist in different structural formula but its molecular formula remains the same.

Question. Why do soaps form scum when added to hard water?
Answer : Hard water contains carbonate and sulphate salts of magnesium or sodium ions which react with the soap molecule to form a compound which is insoluble in water. Hence soaps form scum with hard water.

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. What is hydrophilic?
Answer : The substance showing attraction towards water is called hydrophilic.

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

Short Answer Questions

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

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