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Which of the following is not observed in a homologous series? Give reason for your choice.
(a) Change in chemical properties
(b) Difference in —CH 2 and 14u molecular mass
(c) Gradation in physical properties
(d) Same functional group
Answer
Homologous series is a group/sequence of compounds which have the same functional group and similar chemical properties . The two successive compounds differ by a CH 2 group i.e. 12 + (2 x 1) = 14 amu.
In a homologous series, only the physical properties change . Chemical properties remain the same because of the presence of the same functional group.
Now, let’s check the options
- (a) Change in chemical properties - This is not observed in a homologous series. The chemical properties of all compounds in a homologous series remain the same.
- (b) Difference in —CH 2 and 14u molecular mass - This is observed in a homologous series.
- (c) Gradation in physical properties - This is observed in a homologous series.
- (d) Same functional group - This is observed in a homologous series.
Therefore, the correct option is (a) change in chemical properties
