Tiêu đề Chap. 4 carbon and Its Compounds.pdf ✅

Ch. 4 Carbon and Its Compounds Q1. Which organic compound is added to make ethanol unfit for drinking purposes? What is the name of the mixture formed? Ans. Methanol which is highly poisonous is added in small amount to ethanol in order to make unfit for drinking purposes. The mixture is called methylated spirit or denatured alcohol. Q2. Vapours of a hydrocarbon were passed through bromine dissolve in carbon tetrachloride. The yellow colour of bromine got discharge? Predict the nature of the hydrocarbon. Ans. The hydrocarbon is unsaturated. It is either an alkene or alkyne. Q3. What do we get when ethanoic acid reacts with ethenoil in the presence of concentrated sulphuric acid? Ans. Ethyl ethanoate (CH3COOC2H5) is formed by Esterification reaction. It has fruity smell. Q4. What are the essential constituents of all organic compounds? Ans. Carbon and hydrogen are the essential constituents of all organic compounds. However, carbon tetrachloride (CCl4) is an exception. Q5. What is the valency of carbon in its compounds? Ans. Carbon is tetravalent in its compound. Q6. The formula of a hydrocarbon is CnH2n. Name the family which it belongs and also predict its nature. Ans. The hydrocarbon belongs to alkene family. It is unsaturated in nature. Q9. When do you get yellow soot in a burner? Ans. Yellow soot is obtained when the holes of the burner are not clean. The combustion is incomplete. The yellow soot or yellow flame is because of unburnt carbon particles. Q10. What is the role of soap in cleansing of clothes? Ans. Soap helps in forming a stable emulsion between oil drops carrying dirt particle sand water. The emulsion is also known as micelle. Q11. Give a test to identify the presence of ethanoic acid.
Ans. Dip a strip of blue litmus paper in the solution of ethanoic acid. Its colour will change to red. Q12. Why are organic compounds present in such a large number? Ans. This is due to the self linking property of carbon known as catenation. Q13. Can you check hard water by using a detergent? Ans. No, it is not possible because detergents give lather with both soft and hard waters. Q14. A family of organic compounds has the functional group ‘al’ what is its name? Ans. The family of aldehydes also called alkanals. Q15. Which is common in all the members of a family? Ans. They have the common functional group. Q16. An unknown compound has the smell of vinegar. Identify it. Ans. The is ethanoic acid also called acetic acid. Q17. Why is candle flame generally yellow? Ans. Candle flame is generally yellow due to the presence of unburnt carbon particles. When light falls on these particles, they scatter yellow colour. This shows that the combustion of hydrocarbons present in wax or candle is not complete. Q18. Out of ketonic and aldehydic groups, which is the terminal functional group? O || Ans. Aldehydic group ( – C – H ) is the terminal functional group. Q19. An compound with molecular formula C2H6O is used as a duel. Identify the compound. Ans. The compound is ethanol with formula C2H5OH. Q20. Identify from the following hydrocarbons that undergo edition reactions: C3H4, C2H6, CH4, C2H4. Justify your answer. Ans. The hydrocarbons are C2H4 (ethane) with formula CnH2n and C3H4 (Propyne) with formula CnH2n – 2. Both are unsaturated. Q21. Which ions are responsible for making water hard?
Ans. Ca2+ and Mg2+ ions are responsible for making water hard. Q22. How can saturated and unsaturated hydrocarbons be differentiated on the basis of combustion? Ans. Saturated hydrocarbons sometimes burn with smoky flame upon combustion while unsaturated hydrocarbons always burn with non-smoky or blue flame. This is on account of the reason that for the same number of carbon atoms in their molecular formula, saturated hydrocarbons have more hydrogen atoms as compared to unsaturated hydrocarbons. Q23. Write IUPACV and common names of CH3COCH3, C2H5COOH. Ans. CH3COCH3: propane, Acetone C2H5COOH: Propanoic acid, Propanoic acid. Q24. Which functional groups are present in family of (i) alcohols (ii) aldehydes (iii) carboxylic acids? Ans. (i) –OH (ii) –CHO (iii) –COOH. Q25. The molecular formula of butane is C4H10. What is the formula of butane? Ans. The formula of butane is C4H8. Q26. Which has a triple bond; C2H4, C3H4 and C3H6. Ans. C3H4 has triple bond with the formula CH3C ≡ CH Q27. Which of the following belong to the same homologous series? C3H8, C4H8, C4H6, C3H6. Ans. C3H6 and C4H8 belong to the same homologous series which is alkenes with general formula CnH 2n . Q28. What is common in the structures of the compounds methanol and ethanol? Ans. They have the same functional group (–OH) known as alcoholic group. SHORT ANSWER QUESTIONS Q29. State two characteristics features of carbon which when put together give rise to a large number of carbon compounds. Ans. (i) The size of carbon atom is very small (Atomic radius bonds = 77pm) (ii) The strength C – C bond is quite high (355 kj mol-1 )
Therefore, any number of carbon atoms can be linked by covalent bonds. This self linking property is called catenation. Q30. (a) Why is not easy for carbon to take part in the function of ionic compounds? (b) Diamond is a poor conductor of electricity while graphite is a good conductor. Assign reason. Ans. (a) In order to form ionic bond, carbon atom is either to lose four electrons to form C4+ ion or gain four electrons to form C4- ion. The loss or gain of electron is not easy for carbon since energy needed is very high. It is not available as such. Therefore, carbon does not take part in ionic bond formation. (b) In the structure of diamond, all the four valence electrons of carbon are involved in the formation of covalent bonds. Thus, no free electron is available. In the structure of graphite, three electrons in the valance shell of carbon are involved in covalent bond formation. The fourth electron is free to carry charge. Therefore, graphite is a good conductor of electricity. Q31. The molecular formula C3H6O can represent an aldehydes as well as ketone. Write their structures and name them. How are they related to each other? Ans. The aldehyde and ketone with formula C3H6O are propanal and propane. Having the same molecular formula, these are isomers. As the functional groups are different, these are regarded as functional isomers. For example, O O || || CH3–CH2–C–H and CH3–C–CH3 Propanal Propanone Q32. (a) Hydrocarbons generally act as fuels. How will you account for this? (b) Why is petrol regarded as a better fuel then kerosene? Ans. (a) All hydrocarbons contains carbon and hydrogen. Both these elements are easily oxidised by oxygen to from carbon dioxide and water respectively. These reactions are highly exothermic and are accompanied by the release of large amount of heat energy. That is why hydrocarbons generally act as fuels. (b) In petrol, the combustion of hydrocarbons present is complete and they burn with blue flame. However, in kerosene, the combustion is not complete. It burns with smoky flame accompanied by the release of unburnt carbon atoms. Therefore, petrol is regarded as a better fuel than kerosene.