The half life of a radioactive substance is 14 days. If 48g of this substance is stored, after how many days will 1.5g of the original substance remain?
84 days
70 days
56 days
40 days
Explanation
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Half life = 14 days
Initial mass =48g
Final mass after decay=1.5g
1. 2. 3. 4. 5.
48/2=24/2=12/2=6/2=3/2=1.5
So 5×14=70
I think the answer is 94 days
On the 70th day it will be remaining 3
On the 94tg day it will be remaining 1.5 I.e 48/32
T=14 days
N1=48g
N2=1.5g
from Zhepwo's radioactive equation, you get:
t=(T×logR)/log2
R=N1/N2
R=48g/1.5g
R=32
therefore,
t=(14×log32)/log2
t=70 days
This is an easy problem. After 14 days, the amount remaing is 24g. After 28 days, the amount remaing is 12g. Every 14 days, half of the previous amount remains, so 6g, 3g, and 1.5g remains after 3, 4, and 5 half-lives, so 1.5g remains after 5 * 14 days, or 70 days.
