Class 11 Chemistry Ch-13 Hydrocarbon (VSQ)

Q.1. What is halogen carrier? Give one example.

Answer Answer: A halogen compound used during halogenation of benzene is called halogen carrier e.g. FeCl3.

Q.2. Arrange the following in the increasing order of C–C bond length C2H6, C2H4, C2H2

Answer Answer: C2H2 < C2H4 < C2H6

Q.3. Name the products formed when an ethereal solution containing ethyl iodide and methyl iodide is heated with sodium metal.

Answer Answer: A mixture of ethane, propane and butane is formed.

Q.4. Out of ethylene and acetylene which is more acidic and why ?

Answer Answer: Acetylene, due to greater electronegativity of the sp– hybridized carbon.

Q.5. How can ethylene be converted into ethane ?

Answer Answer: By catalytic reduction with H2 in presence of nickel at 523–573 K.

Q.6. Arrange the following: HCl, HBr, HI, HF in order of decreasing reactivity towards alkenes.

Answer Answer: HI > HBr > HCl> HF

Q.7. Give the structure of the alkene ( C4H8) which adds on HBr in the presence and in the absence of peroxide to give the same product, C4H9Br.

Answer Answer: 2–Butene H3C—CH = CH—CH3 (being symmetrical gives the same product i. e., 2–bromobutane).

Q.8. Name two reagents which can be used to distinguish between ethene and ethyne.

Answer Answer: Tollens’ reagent and ammonical CuCl solution.

Q.9. Can eclipsed and staggered conformations of ethane be isolated? Give reason.

Answer Answer: No, because the difference of energy between these two conformations is very small, so even at room temperature these two interconverts rapidly and hence cannot be isolated.

Q.10. What is Lindlar’s catalyst? What is it used for?

Answer Answer: Pd deposited over CaCO3 or BaSO>sub>4 and partially poisoned by addition of lead acetate or sulphur or quinoline. This is used for partial reduction of alkynes to cis–alkenes.

Q.11. What are the requirements for geometrical isomerism?

Answer Answer: Refer textbook

Q.12. Why is dipole moment of trans-1, 2-dichloroethene zero?

Answer Answer: The two Cl’s of the trans-isomer have equal and opposite bond moments bearing a net zero molecular dipole moments.

Q.13. What happens when benzene is treated with excess of Cl2 in presence of sunlight? Give chemical reaction.

Answer Answer:

Q.14. Arrange the three isomers of pentane in increasing order of their boiling points.

Answer Answer: Isomers are 2-methyl pentane, 2, 3-dimethyl butane and 2, 2-dimethyl butane.
All three are isomers with the same molecular formula but one with least branching will have the highest boiling point, this is due to large surface area and more dispersion, forces.

Q.15. How will you distinguish between CH3CH2C ≡ CH and CH3 —C ≡ C —CH3

Answer Answer:

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