CBSE Class 10 Science Important Questions Chapter 4 Carbon and Its Compounds Part 4

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13. Write three difference between ethanol and ethanoic acid on the basis of chemical properties?

Ans. (i) on adding a small amount of to ethanoic acid gas is evolved with brisk effervescence and no such reaction takes place in case of ethanol

(ii) Ethanol is neutral so does not bring any change in the colour of litmus paper but ethanoic acid is acidic and changes the colour of a blue litmus strip to red when dipped in it.

(iii) Ethanoic acid reacts with NaOH and KOH to form salt and water whereas ethanol fails to react.

14. Given a chemical test to distinguish between

(i) Ethane and ethane

(ii) Ethanol and ethanoic acid

(iii) Soaps and Detergents

Ans. (i) Ethane decolorizes the yellow colour of bromine while ethane does not.

(ii) Ethanoic acid gives a brisk effervescence with sodium hydrogen carbonate while ethanol does not.

(iii) Soaps form curdy white precipitate or scum with hard water while detergents do not form any precipitate.

15. Name the functional groups present in the following compounds? (i)

(ii)

(iii)

Ans. (i)

(ii)

(iii)

16. What are esters? Write an equation to show the formation of ester?

Ans. Esters are pleasant smelling compounds and are commonly used as flavouring agents. Monocarboxylic acids react with alcohol to form esters and water. This reaction is called as esterification

17. What will be the formula and electron dot structure for cyclopentane?

Ans. Formula of cyclopentane is . The electron dot structure cyclopentane is:

Formula of cyclopentane

Formula of Cyclopentane

Formula of cyclopentane

18. How many structural isomers can you draw for pentane? Ans. The isomers are as under:

Structural isomers

Structural Isomers

Structural isomers

19. What is a homologous series? Explain with an example.

Ans. Series of compounds in which the same functional group substitutes for hydrogen in a carbon chain is called homologues series. The difference between the formulae of any two successive members is and difference between the molecular formula is 14 u.

20. How can ethanol and Ethanoic acid be differentiated on the basis of their physical and chemical properties?

Ans. On the basis of physical properties: Melting and boiling points of ethanol is 156 K and 351 K but melting and boiling point of Ethanoic acid is 290 K and 391 K respectively. On the chemical properties: Ethanoic acid reacts with sodium hydrogen carbonate liberating carbon dioxide while ethanol does not.

21. Why are carbon and its compounds used as fuels for most applications?

Ans. Carbon on combustion gives carbon dioxide and water. This reaction is accompanied by evolution of heat and light. The same is true for compounds of carbon. That is why carbon and its compounds are used as fuel for most applications.

22. Explain the formation of scum when hard water is treated with soap.

Ans. Hard water contains hydrogen carbonates, chlorides and sulphates of calcium and magnesium which reacts with soap to form scum. For example, calcium chloride reacts with soap to form scum.

Sodium stearate + Calcium chloride sodium chloride + Calcium stearate (scum)

23. What change will you observe if you test soap with litmus paper (red and blue)?

Ans. Soap is sodium or potassium salt of fatty acid. It is obtained by treating of oil with caustic soda. Sodium stearate is thus a salt of weak acid and strong base. Its water solution will be slightly alkaline and will turn red litmus red.

24. What is hydrogenation? What is its industrial application?

Ans. Unsaturated hydrocarbons add hydrogen in presence of catalysts such as palladium or nickel to give saturated hydrocarbons. This process is called hydrogenation.

It is commercially used for converting vegetable oils to ‘vanaspati’ ghee in presence of nickel as catalyst.

25. Explain in mechanism of the cleaning action of soap.

Ans. Soap are sodium or potassium salt of fatty acids. Two ends of molecules of soap behave differently. This ionic end is hydrophilic and it is oriented towards water. The other hydrocarbon end is hydrophobic and it is oriented towards dirt which is oily in nature. A micelle formation around the oily dirt takes place. When flushed with excess of water, the micelle containing the dirt is removed, thus cleaning the clothes, etc.

26. An organic compound X with a molecular formula C undergoes oxidation with in presence of alkaline to form a compound I X on heating in presence of Cone. 11 at 443 K gives Z. which on reaction with 112 cm presence of 11 gives back ‘X. ‘‘Z’ reacts with Br (aq) and decolorizes it. Identify X, Y, & Z and write the reactions involved.

Ans.

Organic compound X

Organic Compound X

Organic compound X

27. ‘A’ compound works well with hard water. It is used for making shampoos &products for cleaning clothes. A is not 100% biodegradable and causes water pollution. ‘B’ does not work well with hard water. It is 100% biodegradable and does not create water pollution. Identify A & B.

Ans. ‘Y’ will burn with a sooty flame. So it is an unsaturated hydrocarbon.

‘A’ compound works

‘A’ Compound Works

‘A’ compound works

28. A cyclic compound ‘X’ has molecular formula . It is unsaturated and burns with sooty flame. Identify ‘X’ and write its structural formula. Will it decolonze bromine water or not and why?

A cyclic compound

A Cyclic Compound

A cyclic compound

It does not decolorize bromine water because it does not undergo addition reaction.

29. An organic compound ‘A’ is a constituent of antifreeze and has the molecular formula.upon reaction with alkaline the compound ‘A’ is oxidized to another ‘B’ with formula C Identify the compound A’ and ‘B’. Write the chemical equation for the reaction which leads to the formulation of ‘B’

Ans.

30. Two compounds ‘X’ and ‘Y’ have the same formula C One of them reacts with sodium metal to liberate 112 and CO with NaHCO Second one does not reacts with Na metal and NaHCO but undergo hydrolysis with NaOH to form salt of carboxylic acid and compound ‘Z’ which is called wood spirit. Identify ‘X’, ‘Y’, and ‘Z’ and write chemical equation for the reaction involved.

Ans.

31. A compound ‘X’ with molecular formula C burns with a sooty flame. It decolourise bromine water. Identify ‘X’ Will it dissolve in water or not? Will it conduct electricity in aq. Solution? Will it have high melting point or low melting point?

Ans. ‘X’ is ethene. It will neither dissolve in water nor conduct electricity because it is a covalent compound. It has low melting point.

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