NCERT Solutions for Class 10 Science Carbon and its Compounds
Page Number – 61
Q1. What would be the electron dot structure of carbon dioxide which has the formula CO2?
Q2. What would be the electron dot structure of a molecule of Sulphur which is made up of eight atoms of Sulphur?
Page Number – 68
Q1. How many structural isomers can you draw for pentane?
Q2. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Ans. The two main properties which led the carbon to form a huge number of carbon compounds are:
(ii) Tetravalency of Carbon
Q3. What will be the formula and electron dot structure of cyclopentane?
Page Number – 69
Q1. Draw the structures of the following compounds.
(i) Ethanoic acid
Are Structural isomers possible for bromopentane?
Ans. (i) Ethanoic acid
Q2. How would you name the following compounds?
Ans. (i) Bromoethane
Page Number – 71
Q1. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Ans. Oxidation is the addition of Oxygen and removal of hydrogen.
So, during the conversion of Ethanol to ethanoic acid, two hydrogen are removed and One Oxygen is added to ethanol. therefore it is an Oxidation reaction.
Q2. A mixture of oxygen and ethyne is used for welding. Can you tell why a mixture of ethyne and air is not used?
Ans. The production of heat is very important for welding metals. When oxygen and ethyne are burnt, it burns completely and produces a higher temperature than air and ethyne. Therefore a mixture of ethyne and oxygen is used.
Page Number – 74
Q1. How would you distinguish experimentally between an alcohol and a carboxylic acid?
Ans. (i) Reaction with base: Alcohol do not react with base, while carboxylic acid react with base to produce salt and water.
(ii) Reaction with Sodium bicarbonate: Carboxylic acids react with Sodium bicarbonate while alcohol do not react.
Q2. What are oxidising agents?
Ans. Oxidising agents are those compounds which either remove Hydrogen or add oxygen to a compound.
Page Number – 76
Q1. Would you be able to check if water is hard by using a detergent?
Ans. It is not possible to check if water is hard by using a detergent because detergents are ammonium or sulphonate salts of long chain carboxylic acids. Unlike soap, they do not react with calcium and magnesium ions present in hard water to form scum. They give a good amount of lather irrespective of whether the water is hard or soft. This means that detergents can be used in both soft and hard water.
Q2. 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?
Ans. A soap molecule has two parts namely hydrophobic and hydrophilic. With the help of these, it attaches to the grease or dirt particle and forms a cluster called micelle. To Wash away these micelles from the surface of the cloth, It is either scrubbed mechanically or agitated in washing machine.
Q1. Ethane, with the molecular formula C2H6 has:
(a) 6 covalent bonds.
(b) 7 covalent bonds.
(c) 8 covalent bonds.
(d) 9 covalent bonds.
Ans. (b) Ethane has 7 covalent bonds.
Q2. Butanone is a four-carbon compound with the functional group:
(a) carboxylic acid.
Ans. (c) The functional group of butanone is ketone.
Q3. 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.
Q4. Explain the nature of the covalent bond using the bond formation in CH3Cl.
Ans. The bonds that are formed by sharing Electrons are known as covalent bonds. Carbon has 4 electrons in its valence shell to complete its octet, it either need to gain 4 electrons or lose 4 electrons to the other atom. Both these processes are impossible therefore carbon atoms achieve noble gas configuration by sharing 4 electrons with other atoms of itself or atoms of other elements.
Q5. Draw the electron dot structures for:
(a) Ethanoic acid.
Ans. (a) Ethanoic acid
Q6. What is a homologous series? Explain with an example.
Ans. A homologous series is a series of carbon compounds that have different numbers of carbon atoms but contain the same functional group.
Example: Methane (CH4)
There is a difference of −CH2 units between each successive compound.
Q7. How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Ans. Distinction based on physical property :
|Smell||Pungent Smell||Pleasant Smell|
|Melting Point||Lower Melting Point(156K)||Higher Melting Point(290K)|
|Physical State||Solid at Lower Temperature||Liquid|
Distinction based on chemical property :
Carbon dioxide Gas is evolved with brisk effervescence.
CH3COOH + NaHCO3 → CH3COONa + Na + CO2 + H2O
No such reaction noticed in case of ethanol.
C2H5OH + NaHCO3 → No reaction
Q8. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Ans. A soap is a sodium or potassium salt of long chain fatty acids. It has one polar end and one non-polar end. The polar end is hydrophilic in nature i.e., this end is attracted towards water. The non-polar end is hydrophobic, i.e., it is attracted towards hydrocarbons. When soap is added to water, soap molecules arrange themselves in a cluster to keep the non-polar portion out of water such that the non-polar ends are in the interior of the cluster and the polar ends are on the surface of the cluster. Since the dirt present on clothes is insoluble in water, the hydrophobic ends of the clusters attach themselves to the dirt. This cluster formation is called micelle. Michelle will not form in all types of solvents. it will form in such type of solvent in which soap is soluble.
Q9. Why are carbon and its compounds used as fuels for most applications?
Ans. When carbon burns in the presence of oxygen it forms carbon dioxide and water. During this reaction a large amount of heat is released. Saturated hydrocarbons burn with a clean flame and no smoke is produced. Therefore, carbon and its compounds used as fuels for most applications.
Q10. Explain the formation of scum when hard water is treated with soap.
Ans. Hard water contains calcium and magnesium ions. Soap is basically Sodium and potassium salt of higher fatty acid. it does not work properly when the water is hard. Hard water contains salts of calcium and magnesium. When soap is added to hard water, calcium and magnesium ions present in water displace sodium or potassium ions from the soap molecules forming an insoluble substance called scum.
Q11. What change will you observe if you test soap with litmus paper (red and blue)?
Ans. Soap is basic in nature, it will turn red litmus blue. However, the colour of blue litmus will remain blue.
Q12. What is hydrogenation? What is its industrial application?
Ans. Hydrogenation: The addition of hydrogen to unsaturated hydrocarbon in the presence of catalyst is known as hydrogenation.
Unsaturated hydrocarbons are added with hydrogen in the presence of Catalyst Like palladium and nickel to give saturated hydrocarbons.
Q13. Which of the following hydrocarbons undergo addition reactions:
C2H6, C3H8, C3H6, C2H2 and CH4.
Ans. Unsaturated hydrocarbons C3H6, C2H2 undergo addition reactions.
Q14. Give a test that can be used to differentiate chemically between butter and cooking oil.
Ans. When cooking oil is treated with a few drops of Alkaline KMnO4, the pink colour of KMnO4 disappears. With butter the pink colour of KMnO4 does not disappear.
Q15. Explain the mechanism of the cleaning action of soaps.
Ans. Soap Molecules have two ends one with hydrophilic and other with hydrophobic. The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water when scrubbed mechanically or beaten. Hence, the dust particles are easily rinsed away by water.