The half-life of iodine-131 is 8 days. Chan Hee examines two samples of iodine-131.
Sample 1: 10 g
Sample 2: 20 g
What can Chan Hee expect to observe about the samples after 16 days?
A. The mass of iodine-131 in sample 1 will be 7.5 g and in sample 2 will be 16 g.
B. Three-fourths of each sample will have undergone radioactive decay.
C. Ten grams of each sample will have undergone radioactive decay.
D. One-half of each sample will still be iodine-131.
The half-life of iodine-131 is 8 days, which means that after 8 days, half of the iodine-131 will decay. Therefore, after 16 days, another half of the remaining iodine-131 will decay.
For Sample 1:
Initially, there are 10 g of iodine-131. After 8 days, half of it will decay, leaving 5 g. After another 8 days, half of the remaining 5 g will decay, leaving 2.5 g. Therefore, the mass of iodine-131 in Sample 1 after 16 days will be 2.5 g.
For Sample 2:
Initially, there are 20 g of iodine-131. After 8 days, half of it will decay, leaving 10 g. After another 8 days, half of the remaining 10 g will decay, leaving 5 g. Therefore, the mass of iodine-131 in Sample 2 after 16 days will be 5 g.
Therefore, Chan Hee can expect to observe that the mass of iodine-131 in Sample 1 will be 2.5 g and in Sample 2 will be 5 g after 16 days.
Therefore, the correct answer is:
A. The mass of iodine-131 in sample 1 will be 2.5 g and in sample 2 will be 5 g.