NCERT Solutions for Class 10th Science
Chapter 4 – CARBON AND ITS COMPOUNDS
(Complete Downloadable Chapter Solution PDF file is at the bottom of the page)
Q.1 What would be the electron dot structure of carbon dioxide which has the formula CO2?
Q.2 What would be the electron dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (Hint – The eight atoms of sulphur are joined together in the form of a ring).
Q.3 How many structural isomers can you draw for pentane?
Q.4 What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Ans 1) Catenation: It is the ability of carbon to form bonds with other atoms of carbon, giving rise to large molecules. Carbon atoms may be linked by single, double or triple bonds.
2) Tetravalency: Since carbon has a valency of four, it is capable of bonding with four other atoms.
Q.5 What will be the formula and electron dot structure of cyclopentane?
Q.6 Draw the structures for the following compounds.
(i) Ethanoic acid (ii) Bromopentane*
(iii) Butanone (iv) Hexanal.
*Are structural isomers possible for bromopentane?
Q.7 How would you name the following compounds?
(i) CH3-CH2-Br
Q.8 Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Q.9 A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Ans When a mixture of oxygen and ethyne is burnt, complete combustion takes place and the desired temperature of welding is achieved. On the other hand when ethyne is burnt in air, it produces sooty flame due to incomplete combustion which is not hot enough to melt metals for welding. Hence a mixture of ethyne and air is not used for welding.
Q.10 How would you distinguish experimentally between an alcohol and a carboxylic acid?
Q.11 What are oxidising agents?
Ans An oxidising agent is one which oxidises other substances by adding oxygen or removing hydrogen. For example alkaline potassium permanganate (KMnO4) and acidified potassium dichromate (K2Cr2O7) are strong oxidising agents.
Q.12 Would you be able to check if water is hard by using a detergent?
Ans No, we would not be able to check if water is hard by using a detergent because a detergent forms a good amount of lather even with hard water i.e. it is effective in hard water also.
Q.13 People use a 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?
EXERCISES
Q.1 Ethane, with the molecular formula C2H6 has
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.
Q.2 Butanone is a four-carbon compound with the functional group
(a) carboxylic acid.
(b) aldehyde.
(c) ketone.
(d) alcohol.
Ans (c) ketone.
Q.3 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.
Ans (b) the fuel is not burning completely.
Q.4 Explain the nature of the covalent bond using the bond formation in CH3Cl.
Q.5 Draw the electron dot structures for
(a) ethanoic acid.
(b) H2S.
(c) propanone.
(d) F2 .
Q.6 What is an homologous series? Explain with an example.
Ans A series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called a homologous series. In hologous series the chemical property remains same and the successive compounds differ by CH2 group. For examples, alkanes like methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10) are all part of the homologous series with the general formula CnH2n+2 in which successive compounds differ by CH2 group.
Q.7 How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Q.8 Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Q.9 Why are carbon and its compounds used as fuels for most applications?
Q.10 Explain the formation of scum when hard water is treated with soap.
Q.11 What change will you observe if you test soap with litmus paper (red and blue)?
Q.12 What is hydrogenation? What is its industrial application?
Ans Hydrogenation is a process in which hydrogen is added to unsaturated hydrocarbons in the presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This process is generally used in industry to obtain vegetable ghee from vegetable oils.
Q.13 Which of the following hydrocarbons undergo addition reactions:
C2H6, C3H8, C3H6, C2H2 and CH4.
Ans C3H6 and C2H2 will undergo addition reactions as they are unsaturated hydrocarbons.
Q.14 Give a test that can be used to differentiate chemically between butter and cooking oil.
Ans Butter contains saturated compounds whereas cooking oil contains unsaturated compounds. The following tests can be done to distinguish them:
1) Cooking oil decolorises bromine water whereas butter does not decolourises it.
2) As cooking oil has unsaturated compounds, it can be hydrogenated whereas butter can not be hydrogenated.
Q.15 Explain the mechanism of the cleaning action of soaps.