1.
Time 5. What is the slope of the line in number 4? What is the value of the rate constant, k, iIt
km? The Slope is -o.oo3? . The rat e constant. 's o.?3??. 6. Using the relationship between the
half-live and the rate constant (In 2 -kts), determine the half-life of your radioactive substance,tw
7. Is your value of ty consistent with the accepted value of approximately 2.552 minutes for the
halif-life of barium-137? What is the percent error? No, our hak lifevalue was 3.44 minutes,
whicis o.sG2 minutes above the accepted value. 3.lit-2.ssaIx1oo,22.02% 8. What fraction of the
initial activity of your barium sample would remain after 25 minu barium 137 9. Was a good
assumption that the counts in the last five minutes would be due entirey to non-barium sources?
Solution
8) given : n=t(given)/t(half) .
here, n=25/3.114.
. n=8.
now,again: ms/ml=(1/2)^n.
therefore ms/ml=(1/2)^8.
. ms/ml=0.39%.
9) we see that amount of barium left is almost negigible.So yes,we can say that counts in the last
5 minutes would be entirely due to non barium sources.