Rangana has a saturated alcohol X of chemical formula C4H9OH.
(a) Write the chemical formula of a member Y that comes two places after X in the homologous series and state by how much will its molecular mass differ from that of X.
(b) How do the chemical properties of X compare with those of Y? Give reason for your answer.
(c) Write the chemical formula of the product Z formed by heating Y with acidified potassium dichromate. Write the general formula for compounds in the homologous series that Z belongs to.

Solution
The molecular formula of saturated alcohol X is CH₃CH₂CH₂CH₂OH.
(a) The chemical formula of member Y will contain two more carbons and 4 more hydrogens than member X. The molecular formula of Y will be CH₃CH₂CH₂CH₂CH₂CH₂OH.
Since, Y has two more carbons and 4 more hydrogens than member X, its molecular mass will be (12 × 2) + (1 × 4) = 28 u more than member X.

(b) Since both X and Y belong to the same homologous series of saturated alcohols, both will have same chemical properties.

(c) When an alcohol is heated with acidified potassium dichromate, it is oxidised to carboxylic acid. 
 CH₃CH₂CH₂CH₂CH₂CH₂OH $\stackrel{\mathrm{Acidified} {\mathrm{K}}_2{\mathrm{Cr}}_2{\mathrm{O}}_7/∆}{\to }$ CH₃CH₂CH₂CH₂CH₂COOH
                Y                                                                                       Z    
So, the product Z will be hexanoic acid.
The product Z belongs to homologous series of saturated carboxylic acids which have the general formula C_nH_2nO₂., where n = 1, 2, 3,......