Frank Solutions for Chapter 11D Alkynes Class 10 Chemistry ICSE

1. Give the names of the first four members of the homologous series of alkynes. 
First four members of the homologus series of alkynes are : 

2. How is ethyne prepared  in the laboratory ? 
Ethyne is prepared by the reaction of calcium carbide with water 

3. What are addition reactions ? How are addition reactions of ethene different from ethyne ? 
Addition Reactions: The reactions in which molecules of the attacking reagent add across the double or triple bond of an unsaturated compound to yield saturated compound.
In case of ethene the addition occurs due to presence of double bond hence one molecule of the compound is added whereas in case of alkynes there is presence of triple bond hence two molecules of the compound is added. 

4. Write the equations to show what happens when ethyne gas reacts with 
(i) Bromine water
(ii) Excess of hydrochloric acid 

5. How will you convert 
(i) Ethyne to ethane 
(ii) Ethyne to acetaldehyde 

6. Give two chemical tests to distinguish between ethane and ethyne. 
Two chemical tests to distinguish between ethane and ethyne are : 
  1. Bromine water test 
  2. Baeyers  test 

7. Give three points to differentiate between saturated and unsaturated hydrocarbons. 

S. No.

Saturated organic compound

Unsaturated organic compound


All the four valencies of each carbon atom are satisfied by forming single covalent bonds with carbon and with hydrogen atoms

The valencies of at least two carbon atoms are not fully satisfied by the hydrogen atoms


Carbon atoms are joined only by a single covalent bond

Carbon atoms are joined by double covalent bonds or by triple covalent bonds.


Less reactive

More reactive

8. Write the structural formulae and IUPAC name of the second and third homologues. 
Structural formulae and IUPAC name of Second Homologues : 

9. Give the reactions of ethyne with 
(a) Hydrogen 
(b) Water
(c) Bromine 

10. Explain the following : 
(i) Ethene and ethyne burn with sooty luminous flame 
(ii) Ethane does not undergo addition reactions 
(iii) Ethyne is used for welding and cutting metals 
(i) Ethene and ethyne burns with a sooty luminous flame as all the carbon atoms do not get oxidized. 
(ii) Ethane does not undergo addition reaction due to absence of double and triple bond. 
(iii) Ethyne is used for welding and cutting metals as ethylene produce high temperature. 

11. Write three uses of ethyne . 
Uses of ethyne : 
  1. For welding and cutting metals 
  2. For artificial ripening of fruits 
  3. As a general anaesthetic under the name Naracylene. 
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