Assignment:
1) A set of piston rings weighing 120 g was irradiated with neutrons from a nuclear reactor, converting some of the cobalt atoms present in the steel into 60 Co. The irradiation continued until 60Co activity reached 360mCi. The rings were installed in the motor of the automobile that went on to operate during 24 hours under average conditions, after which 0.27 μCi of 60Co of activity were determined in the oil filter. Calculate the wear rate of the piston rings in mg / yr based on the hypothesis that all the metal that was worn was captured in the oil filter.
2) One chemistry had a solution containing various sodium salts and it wanted to determine the total amount of sodium contained in it. It added a certain amount of HCl so as to constitute an excess over the equivalent sodium ion, then added exactly 0.4229 g of pure NaCl, which has a total 22Na activity of 22110 counts / min. (22 Na is a positron emitter with a half-life of 2.6 years). The solution was thoroughly mixed and then evaporated until NaCl crystals were obtained. These were filtered and repeatedly recrystallized until the last batch of pure NaCl was obtained with an activity of 483 counts / min and per gram. What was the mass of sodium ion in the original solution?