Class 10 Science Chapter 4 HOTS Questions - Carbon and Its Compounds

Q1: An organic compound A of molecular formula C₂H₄ on reduction gives another compound B of molecular formula C₂H₆. B on reaction with chlorine in the presence of sunlight gives C of molecular formula C₂H₅Cl.
(i) Name the compounds A, B and C.
(ii) Write chemical equation for the conversion of A to B and name the type of reaction.
Ans: The compound A of molecular formula C₂H₄ is an alkene. Upon reduction with hydrogen, it gives ‘B’ of molecular formula C₂H₆. The compound ‘B’ upon chlorinadon gives ‘C’ of molecular formula C₂H₅Cl.
(i) 

(ii)

The reaction to called addition reaction.

Q2: Name the functional group of organic compounds that can be hydrogenated. With the help of suitable example, explain the process of hydrogenation mentioning the conditions of the reaction and any one change in physical property with the formation of the product. Name any one natural source of organic compounds that are hydrogenated.
Ans: The functional group which can be easily hydrogenated is

The family is known as alkenes. The hydrogenation reaction can be carried by heating a member of the family (e.g. ethene) with hydrogen in the presence of a catalyst like nickel (Ni) For example.
Ethene is an unsaturated hydrocarbon while ethane is of saturated nature.
Edible oils such as coconut oil, olive oil, peanut oil etc. contain atleast one in their molecules. These are regarded as unsaturated compounds. Upon hydrogenation, these get converted into fats which no longer contain any

Q3: An organic compound A’ of molecular formula C₂H₆O on oxidation with dilute alkaline KMnO₄ solution gives an acid ‘B’ with the same number of carbon atoms. Compound A’ is often used for sterilization of skin by doctors. Name the compound. Write the chemical equation involved in the formation of ‘B’ from A.
Ans: The compound ‘B’ should contain a —COOH group as it is an acid. Since it has only two carbon atoms, the other carbon atom must represent CH₃ group. Thus, compound ‘B’ is ethanoic acid (CH₃COOH). The compound A used for the sterilization of skin by doctors is ethanol C₂H₅OH (C₂H₆O). The chemical reaction involved in the oxidation by dilute alkaline KMnO₄ solution also called Baeyers reagent is:

Q4: A to F are the structural formulae of some organic compounds:

(i) Give the letters which represent the same family.
(ii) Give the letters which do not represent hydrocarbons.
(iii) Flow can ‘C’ be converted into A?
Ans:
(i) Letters ‘B’ and ‘D’ represent the family of alkynes.
(ii) Letters ‘E’ and ‘F’ donot represent any hydrocarbon.
(iii) ‘C’ can be converted into ‘A’ by passing hydrogen (H₂) in the presence of Ni at 473 K.

Q5: (a) A test tube contains a brown liquid in it. The colour of the liquid remains the same when methane is passed through it but it disappears when ethene is passed. Suggest the name of the liquid brown in colour. Give the chemical equation involved.
(b) The formula of an ester is C₃H₇COOC₂H₅. Write the formulae of the acid and alcohol from which the ester is prepared.
Ans: (a) The brown liquid seems to be bromine dissolved in water. Methane (CH₄) is a saturated hydrocarbon and does not react with bromine. Ethene (C₂H₄) being unsaturated in nature, decolourises bromine and its colour therefore, disappears.

(b) In an ester, the left side in the molecular formula containing C₃H₇CO is derived from the acid while the right side having OC₂H₅ is from the alcohol. This means that the acid and alcohol participating in the ester are C₃H₇COOH and C₂H₅OH respectively. The formation of ester may be shown as follows: