Question

Why are conventional drying agents such as calcium oxide and phosphorous pentoxide not used for drying moist HCl gas? Give equations.

Answer 1

Both are chemically reactive basic compounds that will react with the acidic HCl gas to form new products instead of just absorbing moisture.

Chemical Equations:

With Quicklime (CaO):

\[\ce{CaO + 2HCl -> CaCl2 + H2O}\]

With Phosphorus pentoxide (P₂O₅):

\[\ce{P2O5 + 3HCl -> POCl3 + 3HPO3}\]