Question

Why is conc. Sulphuric acid used as a drying agent? Is it because it is hygroscopic it will absorb water without forming a solution?

Answer 1

Is it because it is hygroscopic it will absorb water

agreed

without forming a solution? Not sure what you mean. You end up with a more dilute sulfuric acid.

It is usually used as a drying agent for a gas. For example nitrogen, He or Ar are bubbled through c.H2SO4 to dry them when it is essential to have a dry atmosphere for a reaction. It can also be used as a dessicant at the bottom of a dessicator and I have seen it used in an open dish in an oven (not recommended) as a dessicant.

Answer 2

Well deliquescent substances like CaCl2 would absorb water and dissolve readily in it. Sulphuric will just absorb the water it will become dilute but it won't necessarily dissolve in the water forming aa solution. Does that make sense or am I just talking gibberish?

Answer 3

<<Well deliquescent substances like CaCl2 would absorb water and dissolve readily in it. Sulphuric will just absorb the water it will become dilute but it won't necessarily dissolve in the water forming aa solution.>>

Grasping at straws for a difference I think. In both cases the end product is a solution. For CaCl2 (or NaOH or P2O5) you end up with a solution of the drying agent in water. For cH2SO4 you end up with a solution of water in the drying agent (the sulfuric acid).