7. Q. What types of flame produce by burning of Benzene, Nepthline and Camphor?
Ans: Smoky flame due presence of excess carbon content.
8. Q. What is Gasol?
Ans: The mixture of petrol with alcohol up to 20% is known gasol.
9.Q. Why Acetic acid is called glacier acid?
Ans: Acetic acid freezes at 290K in cold weather and form crystals.This is why acetic acid is called glacier acid.
10. Q. What is saponification?
Ans: When sodium hydroxide react with ester and form alcohol and sodium Ethanoate. This reaction is used to form soap So this reaction is known as saponification.
CH3COO C2H5 + NaOH ------------> CH3COONa + C2H5OH 11. Q. Why does melting and boiling points of the member of Homologous Series increase gradually ?
Ans: The number of carbon atoms in the molecule of the member of Homologous Series increases gradually
12. Q. Why does the viscosity of the member of Homologous Series increase gradually?
Ans: The viscosity increases as relative molecular mass and size increases.
13. Q. Why alkanes cannot dissolve in water but is soluble in organic solvent?
Ans: This is because alkane does not release a sufficient amount of energy to break the hydrogen bonds in water. Therefore, the alkane does not dissolve.
14. Q. Why doesn’t soap form micelles in ethanol as they form in water?
Ans: In organic solvent like ethanol, soap is completely soluble, hence no micelle formation
15. Q. What is observed on adding 5% solution of alkaline potassium permanganate solution drop by drop to some warm ethanol taken in testube. Write the name of the compound formed during chemical reaction.
Ans: When a 5% solution of alkaline potassium permanganate solution is added drop by drop to some warm ethanol taken in a test tube, magenta colour of alkaline potassium permanganate disappears and ethanol has been changed to carboxylic acid.
The reaction is as follows. CH3 - CH2OH --------------- > CH3COOH
16. Q. How would you distinguish experimentally between an alcohol and a carboxylic acid on the basis of a chemical property?
Ans: we take alcohol and a carboxylic acid in two separate test tubes. Add sodium hydrogen carbonate in both the test tubes. The test tube, from which the effectiveness evolves, contains carboxylic acid. The effervescence is due to the evolution of carbon dioxide gas. However, from test tube containing alcohol there is to effervescence, because no carbon dioxide gas is produced there.
17. Q. A straight-chain alkane will have a boiling point higher than a branched-chain alkane?
Ans: This is due to the greater surface area in contact.
18. Q. Why do Alkanes stable and less reactive than alkenes ?
Ans: This is because saturated hydrocarbons contain only single bonds which are very stable and difficult to break. On the other hand, unsaturated hydrocarbons contain pie bonds, which can be easily broken as they are more strained.
19. Q. How can you check which one is saturated butter or vegetable oil?
Ans: Butter contain saturated compound where as cooking oil contain unsaturated compound. If Alkaline KMno4added to both, pink color of KMno4disappear in cooking oil but remain in pink in butter.
22. Q. Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Ans. When ethanol is oxidised, hydrogen is removed from its molecule and oxygen is added so as to form ethanoic acid. Thus, conversion of ethanol into acetic acid is an oxidation reaction.
23. Q. A mixture of ethyne and oxygen is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Ans: Ethyne is un saturated carbon compound and burns in air with a sooty flame, because the oxygen from air is insufficient to burn the carbon completely. Thus, pure oxygen is used which completely burns carbon and hydrogen and produces a very hot flame.
24. Q. How will you distinguish between alcohol and carboxylic acid experimentally? (V. Imp.)
Ans. Take two test tubes A and B and place about 1 g of sodium carbonate in them. Pour alcohol in test tube A and carboxylic acid in test tube B. Shake the contents of the test tubes.
The test tube in which a brisk effervescence takes place, with the liberation of a colourless gas (CO2) is carboxylic acid. The test tube in which no reaction takes place is alcohol.
25. Q. Unsaturated hydrocarbons show addition reactions but not saturated hydrocarbons?
Ans: in saturated hydrocarbons all the four bonds of carbon are fully utilised and no more hydrogen or other atoms can attach to it. Thus, they can undergo only substitution reactions not addition reactions.
26. Q. How can ethanol and ethanoic acid be differentiated on the basis of physical and chemical properties?
Ans. Physical properties :
(a). Ethanol has a sharp bitter burning taste, whereas ethanoic acid has a sour taste.
(b) On cooling ethanol does not freeze, but ethanoic acid freezes.
Chemical Properties :
(a) Ethanol gets dehydrated by conc. sulphuric acid, but ethanoic acid does not get dehydrated by conc. sulphuric acid.
(b) Ethanol does not displace hydrogen with zinc or magnesium, but ethanoic acid displaces hydrogen with zinc or magnesium
27. Q. ‘‘Saturated hydrocarbons burn with a blue flame while unsaturated hydrocarbons burn with a sooty flame’’. Why?
Ans. This is because unsaturated hydrocarbon has high concentration of carbon than that of unsaturated hydrocarbons
28. Q. Why is the reaction between methane and chlorine considered as a substitution reaction.?
Ans: reaction between methane and chlorine is considered as a substitution reaction since the hydrogen atoms of methane are replaced by chlorine atoms.
29. Q. How would you bring about the following conversions? Name the process and write the reaction involved. (a) ethanol to ethene (b) propanol to propanoic acid.
Ans. (a) By the dehydration of ethanol in the presence of concentrated H2SO4