Which out of the following is the strongest acid?

$\left(\mathrm{i}\right)$ ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}$
$\left(\mathrm{ii}\right)$ ${\mathrm{CH}}_3\mathrm{COOH}$
$\left(\mathrm{iii}\right)$ ${\mathrm{C}}_6{\mathrm{H}}_5\mathrm{OH}$
$\left(\mathrm{iv}\right)$ ${\mathrm{H}}_2\mathrm{O}$

Arrange the following in the increasing order of acid strengths:
$\left(\mathrm{i}\right)$ Fluoroacetic acid

$\left(\mathrm{ii}\right)$ Chloroacetic acid

$\left(\mathrm{iii}\right)$ Acetic acid

$\left(\mathrm{iv}\right)$ Formic acid

$\left(\mathrm{v}\right)$ Propionic acid.

How is benzoic acid converted to Benzoic anhydride?

How is benzoic acid converted to Benzaldehyde ?