Question 9: Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer: The conversion of ethanol to ethanoic acid is as follows:
CH3CH2OH + (Alkaline KMnO4 ) ⇨ CH3COOH
Since, in this reaction one oxygen is added to ethanol, hence it is an oxidation reaction.
Question 10: A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Answer: When mixture of oxygen and ethyne is burnt, it gives high temperature because of complete combustion and gives clean flame. But when ethyne is burnt with air, it results in incomplete combustion. Incomplete combustion will not give a high temperature simultaneously it will give sooty flame. This is the reason, oxygen is used; instead of air; to burn ethyne.
Question 11: How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer: When acid reacts with carbonate and hydrogen carbonate, it gives carbon dioxide which turns lime water milky. On the other hand, alcohol does not give carbon dioxide on reaction with carbonate or hydrogen carbonate. Thus, the reaction with carbonate or hydrogen carbonate; can be used to distinguish between carboxylic acid and alcohol.
Question 12: What are oxidising agents?
Answer: Substances which give oxygen or replace hydrogen on reaction with other compounds are called oxidising agents, example; potassium permanganate.
Question 13: Would you be able to check if water is hard by using a detergent?
Answer: Detergent gives lather with hard and soft water both, while a soap gives lather with soft water only. Thus, it is not possible to check if water is hard; by using a detergent.
Question 14: 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?
Answer: Molecules of soap form micelles with dirt, such as grease. Micelles remain suspended as colloid. To remove dirt in the form of micelles from clothes agitation is necessary to get clean clothes.
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