Question

why does PH3 fumes in moist air?

Answer 1

In the presence of moisture, the hydrolysis of PCl3 gives fumes of phosphorus acid and hydrochloric acid.

Answer 2

PH3 fumes in moist air because of the following chemical reaction :

Phosphine reacts with water to UNDERGO HYDROLYSIS

reaction  to produce to hydrogen chloride and phosphorous

acid

This Hydrogen chloride which is liberated fumes in air.

PH3 +3H20---->H3P03+3HCl