What is the half life of the following radioactive decay? And is 5.78e-3 the cor
ID: 1271652 • Letter: W
Question
What is the half life of the following radioactive decay? And is 5.78e-3 the correct decay constant?
Data Table 1: Radioactive Decay
Trials
Time-minutes
Parents=peas lying flat # per trial
Daughters=Peas on rounded side
# per trial : cumul.
0
0
50
0 0
1
2
15
35 35
2
4
4
11 46
3
6
3
1 47
4
8
2
1 48
5
10
1
1 49
6
12
0
1 50
Trials
Time-minutes
Parents=peas lying flat # per trial
Daughters=Peas on rounded side
# per trial : cumul.
0
0
50
0 0
1
2
15
35 35
2
4
4
11 46
3
6
3
1 47
4
8
2
1 48
5
10
1
1 49
6
12
0
1 50
Explanation / Answer
A radioactive decay follows first order kinectics.
Thus the equation is N = N0e-kt
Here N0 is the number of parent nuclei at the start or at time = 0.
N is the number of parent nuclei at time = t.
k = decay constant
Form reading one we have N0 = 50.
from 2nd observation we get at time t = 2min = 120 sec we have parent nuclei(N) = 15.
Put in above equation
15 = 50*e-k*120
-1.2 = - k*120
k = 0.01sec-1
half life = ln2/k = 0.693/0.01 = 69.3sec = 1.155min
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