Carbon and Its Compounds NCERT Exemplar Problems
Short Answer Part 1
Question 1: A compound X is formed by the reaction of a carboxylic acid C2H4O2 and an alcohol in presence of a few drops of H2SO4. The alcohol on oxidation with alkaline KMnO4 followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of (a) carboxylic acid, (b) alcohol and (c) the compound X. Also write the reaction.
Answer: The carboxylic acid is ethanoic acid, the alcohol is ethyl alcohol and compound X is ester. The reaction is as follows:
CH3COOH + CH3 → CH3COOCH2CH3
Question 2: Why detergents are better cleansing agents than soaps? Explain.
Answer: Soaps can work properly only in soft water but not in hard water. This happens because soap forms precipitate after reacting with magnesium and calcium salts which are present in hard water. But detergents work equally good in soft water and hard water because they do not form precipitate even in hard water. Hence, detergents are better cleansing agents than soaps.
Question 3: Write the names of the following compounds
Answer: Pentaoic acid
Answer: Butyne
Answer: Heptanal
Answer: Pentanol
Question 4: Draw the electron dot structure of ethyne and also draw its structural formula
Answer:
Question 5: Identify and name the functional groups present in the following compounds.
Answer: Hydroxyl
Answer: Carboxylic acid
Answer: Ketone
Answer: Alkene
Question 6: Name the functional groups present in the following compounds
- CH3COCH2CH2CH2CH3
Answer: Ketone - CH3CH2CH2COOH
Answer: Carboxylic acid - CH3CH2CH2CH2CHO
Answer: Aldehyde - CH3CH2OH
Answer: Alcohol
Question 7: How is ethene prepared from ethanol? Give the reaction involved in it.
Answer: When ethanol is heated with excess of concentrated sulphuric acid at 443 K; it produces ethene. Hydrolysis of ethanol is involved in this reaction. This can be shown by following equation.
CH3CH2OH + hot conc. H2SO4 at 443 K → H2C=CH2 + H2
Question 8: Intake of small quantity of methanol can be lethal. Comment.
Answer: Methanol gets oxidized into methanal when it goes to the liver. Methanal results in coagulation of the protoplasm of cells. Moreover, it also affects the optic nerve and causes blindness. These effects of methanol make it lethal.
Question 9: A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.
Answer: Hydrogen gas is evolved in this reaction. This reaction can be shown by following equation.
2CH3CH2OH + 2Na → 2CH3CH2ONa + H2