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प्रश्न
Write a short note.
Homologous series
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उत्तर
- The series of carbon compounds formed by joining the same functional group in the place of a particular hydrogen atom on the carbon chains having sequentially increasing length is called homologous series.
- There are different homologous series in accordance with the functional group. For example, homologous series of alcohols, homologous series of carboxylic acids, homologous series of aldehydes, etc.
- All the members of the homologous series are homologues of each other and they can be represented by the same general molecular formula.
- Physical properties generally show a gradual change with the increase in molecular mass in the series whereas chemical properties of the members of the series show similarity because of the presence of the same functional group in them.
APPEARS IN
संबंधित प्रश्न
What is a homologous series?
State any four characteristics of a homologous series
Write the next homologue of the following: C2H4
Write the name and formula of the 2nd member of homologous series having general formula CnH2n – 2.
The following vegetables are kept in a basket :
Potato, Tomato, Radish, Brinjal, Carrot, Bottle-gourd
Which two of these vegetables correctly represent the homologous structures?
(A) Carrot and Tomato
(B) Potato and Brinjal
(C) Radish and Carrot
(D) Radish and Bottle-gourd
Give the structural formula for 1, 2-dichloroethane
Fill in the following blank with suitable word:
Carbon compounds have usually ... melting points and boiling points because they are ...... in nature.
What is the next higher homologue of methanol (CH3OH)?
An organic compound having the molecular formula C3H6O can exist in the form of two isomers A and B having different functional groups. The isomer A is a liquid which is used as a solvent for nail polish. The isomer B is also a liquid. An aqueous solution of one of the lower homologues of B is used for preserving biological specimens in the laboratory
(a) What is compound A?
(b) Write the electron-dot structure of A.
(c) What is compound B?
(d) Write the electron-dot structure of B.
(e) Name the lower homologue of compound B which is used in preserving biological specimens.
A colourless organic liquid X of molecular formula C2H4O2 turns blue litmus to red. Another colourless organic liquid Y of molecular formula C3H6O has no action on any litmus but it is used as a nail polish remover. A yet another colourless organic liquid Z of molecular formula C2H6O has also no action on litmus but it is used in tincture of iodine.
(a) Name the liquid X. To which homologous series does it belong? Give the name of another member of this homologous series.
(b) Name the liquid Y. To which homologous series does it belong? Write the name of another member of this homologous series.
(c) Can you name an organic compound having the same molecular formula as liquid Y but which belongs to a different homologous series? What is this homologous series?
(d) Name the liquid Z. To which homologous series does it belong? Write the name of another member of this homologous series.
Give the dot diagram of the first member of the alcohol.
Give the abbreviated formula of the third member of the alcohol.
.
Why homologous series of carbon compounds are so called? Write chemical formula of two consecutive members of a homologous series and state the part of these compounds that determines their (i) physical properties, and (ii) chemical properties.
Define homologous series of organic compounds. List its two characteristics. Write the name and formula of the first member of the series of alkenes.
Distinguish between homologous organs and analogous organs. In which category would you place wings of a bird and wings of a bat? Justify your answer giving a suitable reason.
What is the difference in the molecular formula of any two adjacent homologues:
(i) In terms of molecular mass
(ii) In terms of number and kind of atoms per molecule?
The general formula of Alkane is _________________
Complete the following table for homologous series of alcohols.
| Name | Molecular formula | Condensed structural formula | Number of carbon atom | Number of -CH2- units | Boiling point °C |
| Methanol | CH4O | CH3-OH | 1 | 1 | 63 |
| Ethanol | C2H6O | CH3–CH2-OH | 2 | 2 | 78 |
| Propanol | C3H8O | CH3–CH2–CH2-OH | ______ | ______ | 97 |
| Butanol | C4H10O | CH3–CH2–CH2–CH2–OH | ______ | ______ | 118 |
