Question

What's the difference between pure sulfuric acid and impure sulfuric acid?

Answer 1

Sulfuric acid  is a mineral acid with the molecular formula H2SO4. It is a colorless odorless syrupy liquid that is soluble in water.

Its corrosiveness can be mainly ascribed to its strong acidic nature. It readily absorb water vapour from the air. Sulfuric acid at even moderate concentrations is very dangerous upon contact with skin.  

For impure u need PH

Answer 2

Answer:

Pure sulfuric acid has a vapor pressure of <0.001 mmHg at 25 °C and 1 mmHg at 145.8 °C, and 98% sulfuric acid has a <1 mmHg vapor pressure at 40 °C. Pure sulfuric acid is a viscous clear liquid, like oil, and this explains the old name of the acid ('oil of vitriol').