Question

A certain radioactive element has a half-life of one hour. if you start with 1.0 gram of the element at noon, how much of the radioactive element will be left at 2 p.m.? 0.50 grams 0.25 grams 0.125 grams 0.0 grams

Answer 1

Answer:

The radioactive element will be left at 2 p.m. will be 0.25 g.

Explanation:

Half life of the radioactive element =$t_{\frac{1}{2}}=1 hour$

Initial concentration of the radioactive element = $N_o$=1.0 g

Time elapsed = 12:00 pm to 2:00 pm = 2 hours

Concentration of radioactive element left = N

$\lambda =\frac{0.693}{t_{\frac{1}{2}}}=\frac{0.693}{1 hr}=0.693 hr^{-1}$

$\log N=\log N_o-\frac{\lambda t}{2.303}$

Putting the given values in the above equation we get:

N = 0.25 gram

The radioactive element will be left at 2 p.m. will be 0.25 g.

Answer 2

Answer: 0.25 g
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