1 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
1/8th of a mg. You lose half every three hours.
2.5
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.
1 mg
0.25
0.25 mg
1 mg
.25 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.
After 3 half-lives, half of the original sample would remain unchanged. After the 1st half-life: 300 unchanged atoms. After the 2nd half-life: 150 unchanged atoms. After the 3rd half-life: 75 unchanged atoms would remain.
To determine how much of a 100 gram sample would remain unchanged after 2 hours, it is necessary to know the specific decay rate or change process of the sample. For example, if the sample undergoes a decay process with a known half-life, you can calculate the remaining amount using the formula for exponential decay. Without this information, it's impossible to provide an exact answer. In general, if no decay occurs, the entire 100 grams would remain unchanged.