问题描述：
有关化学的英文题目(中英文回答都可以)
1.If you started with 100 grams of a substance having a half-life of 2.5 hours,how much of the original substance would remain after 5 hours?7.5 hours?
2.If a radioactive substance has an extremely long half-life,would you expect its activity to be hogh or low?
1.If you started with 100 grams of a substance having a half-life of 2.5 hours,how much of the original substance would remain after 5 hours?7.5 hours?
2.If a radioactive substance has an extremely long half-life,would you expect its activity to be hogh or low?
问题解答：
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