Under certain water conditions, the free chlorine
(hypochlorous acid, HOCl) in a swimming pool decomposes according
to the law of uninhibited decay. After shocking a pool, the pool
boy, Geoff, tested the water and found the amount of free chlorine
to be 2.4 parts per million (ppm). Twenty-four hours later,
Geoff tested the water again and found the amount of free chlorine
to be 2.1 ppm. What will be the reading after 2 days (that is, 48
hours)? When...