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Question
Ten grams of 57Co kept in an open container beta-decays with a half-life of 270 days. The weight of the material inside the container after 540 days will be very nearly
Options
10 g
5 g
2.5 g
1.25 g
Solution
10 g
57Co is undergoing beta decay, i.e. electron is being produced. But an electron has very less mass (9.11×10-31 kg) as compared to the Co atom. Therefore, after 570 days, even though the atoms undergo large beta decay, the weight of the material in the container will be nearly 10 g.
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