Identify the molecular formula of pyridine from the following.

The cyclopentadienyl anion is:

What is the expected order of reactivity of the following compounds in electrophilic chlorination $(Cl_2 + FeCl_3)$? (more reactive $ > $ less reactive)
$I: C_6H_5CH_2CO_2H$
$II: C_6H_5N(CH_3)_2$
$III: C_6H_5OCOCH_3$
$IV: C_6H_5CCl_3$

The major product $P$ formed in the following reaction is:

Nitrobenzene can be prepared from benzene by using a mixture of conc. $HNO_3$ and conc. $H_2SO_4$. In the mixture,nitric acid acts as a/an

Benzene was discovered by.....