The half-life of Cu-61 is approximately 3 hours, meaning that after each half-life, half of the remaining sample decays. After 9 hours, which is three half-lives (3 hours x 3 = 9 hours), the original 2 mg sample would have gone through three decay cycles. Thus, the amount remaining would be (2 , \text{mg} \times \left(\frac{1}{2}\right)^3 = 2 , \text{mg} \times \frac{1}{8} = 0.25 , \text{mg}).
Copper-64 (Cu-64) has a half-life of approximately 12.7 hours. After one half-life (12.7 hours), half of the original sample would remain. Therefore, from a 2 mg sample, after 12 hours, approximately 1 mg of Cu-64 would remain, as it has not yet fully completed one full half-life.
0.25
1 mg
1 mg
1/8th of a mg. You lose half every three hours.
After 132 hours, 1/4 of the initial sample of 10 Ci of Mo-99 would remain. Since the half-life is 66 hours, after 66 hours half of the sample would remain (5 Ci), and after another 66 hours (totaling 132 hours), half of that remaining amount would be left.
Copper-64 (Cu-64) has a half-life of approximately 12.7 hours. After one half-life (12.7 hours), half of the original sample would remain. Therefore, from a 2 mg sample, after 12 hours, approximately 1 mg of Cu-64 would remain, as it has not yet fully completed one full half-life.
1 mg
1 mg
0.25
.25 mg
0.25 mg
1 mg
1 mg
1/8th of a mg. You lose half every three hours.
2.5
To determine the remaining mass of a 10-gram sample of (^{42}\text{K}) after 12.4 hours, we need to know its half-life. The half-life of (^{42}\text{K}) is approximately 12.36 hours. After 12.4 hours, which is slightly more than one half-life, the mass will be reduced to about half of the initial mass. Thus, approximately 5 grams of the original 10-gram sample will remain unchanged after 12.4 hours.