Carbon and its Compounds — Class 10 Science PYQs

Consider the following statements about homologous series of carbon compounds :
(a) All succeeding members differ by $-{\text{CH}}_2$ unit.
(b) Melting point and boiling point increases with increasing molecular mass.
(c) The difference in molecular masses between two successive members is $16\text{ u}$.
(d) ${\text{C}}_2{\text{H}}_2$ and ${\text{C}}_3{\text{H}}_4$ are NOT the successive members of alkyne series.
The correct statements are –

The name and formula of third member of homologous series of alkyne is :

Carbon compounds :
(i) are good conductors of electricity.
(ii) are bad conductors of electricity.
(iii) have strong forces of attraction between their molecules.
(iv) have weak forces of attraction between their molecules.

The correct statements are :

Consider the following statements about homologous series of carbon compounds :
(a) All succeeding members differ by $-{\text{CH}}_2$ unit.
(b) Melting point and boiling point increases with increasing molecular mass.
(c) The difference in molecular masses between two successive members is $16\text{ u}$.
(d) ${\text{C}}_2{\text{H}}_2$ and ${\text{C}}_3{\text{H}}_4$ are NOT the successive members of alkyne series.

The correct statements are -

(A) (i) Define the term functional group. Identify the functional groups present in the following carbon compounds :

   H O H
   | || |
 H-C-C-C-H
   |    |
   H    H
      (I)

   H H OH
   | | |
 H-C-C-C=O
   | |
   H H
      (II)

(ii) What happens when ethanol reacts with acidified potassium dichromate solution ? Write chemical equation for the reaction. Why is this reaction considered an oxidation reaction ?
(iii) Write chemical equation for the reaction of ethanoic acid with sodium hydroxide.
OR
(B) (i) Describe method of preparation of soap giving chemical equation for the reaction involved.
(ii) Explain with diagram the mechanism of the cleansing action of soaps.

(a) (i) Give reason why carbon can neither form ${\text{C}}^{4+}$ cations nor ${\text{C}}^{4-}$ anions but form covalent compounds.
(ii) What is homologous series of carbon compound ? Write the molecular formula of any two consecutive members of homologous series of aldehydes.
(iii) Draw the structure of the molecule of cyclohexane (${\text{C}}_6{\text{H}}_{12}$).

OR

(b) (i) Name a commercially important carbon compound having functional group $-\text{OH}$ and write its molecular formula.
(ii) Write chemical equation to show its reaction with
(1) Sodium metal
(2) Excess conc. sulphuric acid
(3) Ethanoic acid in the presence of an acid catalyst
(4) Acidified potassium dichromate
Also write the name of the product formed in each case.

(a) (i) Give reason why carbon can neither form ${\text{C}}^{4+}$ cations nor ${\text{C}}^{4-}$ anions but form covalent compounds.
(ii) What is homologous series of carbon compound ? Write the molecular formula of any two consecutive members of homologous series of aldehydes.
(iii) Draw the structure of the molecule of cyclohexane (${\text{C}}_6{\text{H}}_{12}$).

OR

(b) (i) Name a commercially important carbon compound having functional group $-\text{OH}$ and write its molecular formula.
(ii) Write chemical equation to show its reaction with
(1) Sodium metal
(2) Excess conc. sulphuric acid
(3) Ethanoic acid in the presence of an acid catalyst
(4) Acidified potassium dichromate
Also write the name of the product formed in each case.

(A) (i) Define a homologous series of carbon compounds.
(ii) Why is the melting and boiling points of ${\text{C}}_4{\text{H}}_8$ higher than that of ${\text{C}}_3{\text{H}}_6$ or ${\text{C}}_2{\text{H}}_4$ ?
(iii) Why do we NOT see any gradation in chemical properties of a homologous series compounds ?
(iv) Write the name and structures of (i) aldehyde and (ii) ketone with molecular form ${\text{C}}_3{\text{H}}_6\text{O}$.

OR

(B) (i) Write the name and structure of an organic compound 'X' having two carbon atoms in its molecule and its name is suffixed with '-ol'.
(ii) What happens when 'X' is heated with excess concentrated sulphuric acid at $443\text{ K}$ ? Write chemical equation for the reaction stating the conditions for the reaction. Also state the role played by concentrated sulphuric acid in the reaction.
(iii) Name and draw the electron dot structure of hydrocarbon produced in the above reaction.