How could gas-density measurements help to establish that PCl5 vapor is decomposing?

Phosphorus pentachloride is a white solid that sublimes (vaporizes without melting) at about 100 degrees C. At higher temperatures, the PCl5 vapor decomposes to give phosphorus trichloride and chlorine.

How could gas-density measurements help to establish that PCl5 vapor is decomposing?

1 Answer
Dec 9, 2016

Answer:

The average gas-density of the air(?) around the reaction will increase as #PCl_3 and Cl_2# are added to it.

Explanation:

Of course, that will not necessarily be conclusive evidence that the #PCl_5# is decomposing , instead of just subliming. A specific test for chlorine in the surrounding gas would be more conclusive.