Give reasons for the following : (i) Unsaturated hydrocarbons show addition reactions. (ii) Detergents are better…

(a)
A - $\ce{C2H5OH}$/ Ethanol ($\frac{1}{2}$)
$\ce{H \quad H}$
$\ce{| \quad |}$
$\ce{H-C-C-OH}$
$\ce{| \quad |}$
$\ce{H \quad H}$ ($\frac{1}{2}$)
B - $\ce{CH3COOH}$ /Ethanoic acid/ acetic acid ($\frac{1}{2}$)
$\ce{H \quad O}$
$\ce{| \quad ||}$
$\ce{H-C-C-OH}$
$\ce{|}$
$\ce{H}$ ($\frac{1}{2}$)
C- $\ce{CH3COOC2H5}$ /Ethyl ethanoate/ ethyl acetate/ester ($\frac{1}{2}$)
$\ce{H \quad O \quad H \quad H}$
$\ce{| \quad || \quad | \quad |}$
$\ce{H-C-C-O-C-C-H}$
$\ce{| \quad \quad \quad | \quad |}$
$\ce{H \quad \quad \quad H \quad H}$ ($\frac{1}{2}$)
Alternate answer
$\ce{C2H5OH ->[Acidified K2Cr2O7] CH3COOH}$
Ethanol(A) Ethanoic acid (B) (1+1)
$\ce{A + B ->[conc H2SO4] C (CH3COOC2H5)}$
Ester
Ethyl ethanoate/ethyl acetate (1)
OR
(b)
(i) Unsaturated hydrocarbons having double or triple bonds have a
strong tendency to become saturated. (1)
OR
Unsaturated hydrocarbons are reactive and undergo addition
reactions. (1)
(ii) Long chain of hydrocarbon in detergents does not form insoluble
precipitate with Calcium or Magnesium ions of hard water and hence
they remain effective even in hard water. (1)
(iii) Carbon is tetravalent. It can neither form $\ce{C4+}$ cation nor $\ce{C4-}$ anion.
It completes its octet by sharing its valence electrons with other atoms
of carbon or other elements forming covalent bonds. (1)