______ is used to prepare fire proof and water proof clothes.

Chemically, why can't liquid detergent be used on waterproof clothing but powder detergent can be? I'm assuming that the hydrophilic end of the liquid detergent remains on the clothing, but I'm looking for a deeper answer. Does the powdered detergent not leave a hydrophilic residue? How come? Or am I completely wrong? This has nothing to do with school, I was just getting my snowboarding clothes ready for the season and I'm a senior Chemistry major so I'm curious...

What volume of 8.4 N Al(OH)3 will be used to prepare 350 mL of 2.1 M solution?
How many mL of water will be used to prepare this dilute solution?