Why is the viscosity and boiling point of concentrated `H_(2)SO_(4)` very high?

Explanation

The structure of sulphuric acid is as follows:

Each molecule of `H_(2)SO_(4)` contains two OH groups and two doubly bonded oxygen atoms. Thus, each molecule of `H_(2)SO_(4)` forms four H-bonds with other molecules. this causes extensive association among the `H_(2)SO_(4)` molecules, resulting in increase in boililng point.

The extensive intermolecular H-bonding enhances the intermolecular attraction among the different layers of the liquid, leading to incrase in viscosity.