Sodium-25 was to be used in an experiment but it took 3.0 minutes to get the sodium from the reactor to the laboratory if 5.0 mg of sodium-25 was removed from the reactor how many mg of sodium-25 were placed in the reaction vessel 3.0 minutes later if the half-life of sodium-25 is 60 seconds

3 half lives later... 5/2 = 2.5mg, then 2.5/2 = 1.25 mg, then 1.25/2 = .625 mg left

The mass has escaped into a gas which you can not see so the law stays true.

Ans. : frostbite is when exposure to cold temperatures causes freezing to the skin or other tissues. it most commonly affects the hands, feet, and face. the longer areas are exposed to cold, typically the worse the frostbite. the water temperature used for rewarming a frostbitten part should be : (102 -105) f degrees.