Question

explain why it is a common laboratory procedure to heat analytical reagents and store them in a dessicated atmosphere (a sealed environment containing a dehumidifying agent) before use.

Answer 1

Explanation:

Most reagent forms are going to absorb water from the air; they're called "hygroscopic".  Water presence can have a drastic impact on the experiment being performed  For fact, it increases the reagent's molecular weight, meaning that anything involving a very specific molarity (the amount of molecules in the final solution) will not function properly.

Heating will help to eliminate water, although some chemicals don't react well to heat, so it shouldn't be used for all.  A dessicated environment is simply a means to  "dry."  That allows the reagent with little water in the air to attach with.