Krypton-81m is inhaled during studies to measure lung ventilation. Its half-life is only 13 seconds. How much time has passed before a sample of krypton-81m with an original activity of 260 decays per minute has decreased to an activity of 8 decays per minute?
2007-05-21 10:41:13 · 3 answers · asked by soccrrulz21 2 in Science & Mathematics ➔ Chemistry
260/8 = 65/2 times = 32. 5 times
Each 13 seconds, the activity becomes half.
So, in 26 seconds, it becomes 1/4th.
in 39 seconds, it becomes 1/8th
in 52 seconds, it becomes 1/16th
in 65 seconds, it becomes 1/32th
So, just a little beyond 65 seconds have passed. A more precise answer is possible with logarithms and a scientific calculator.
2007-05-21 10:51:53 · answer #1 · answered by Swamy 7 · 0⤊ 0⤋
8 = 260 (1/2)^ (13/x)
2007-05-21 17:49:06 · answer #2 · answered by stephanie l 5 · 0⤊ 0⤋
260/2= 130
130/2=65
65/2=32.5
32.5/2=16.25
16.25/2=8.125
soooo the answer is 5 x 13 secs my friend
= 65 secondos.
2007-05-21 17:54:07 · answer #3 · answered by Dave K 2 · 0⤊ 0⤋