11)A radioactive sample contains 1.95 g of an isotope with a half-life of 3.7 da
ID: 1024037 • Letter: 1
Question
11)A radioactive sample contains 1.95 g of an isotope with a half-life of 3.7 days. What mass of the isotope will remain after 5.6 days? (Assume no excretion of the nuclide from the body.) Express your answer using two significant figures.
14) In another process in which 235 92U undergoes neutron bombardment, the following reaction occurs: 235 92U+10nAZSr+143 54Xe+310n Enter the isotope symbol for the strontium (Sr) nucleus in this reaction. Express your answer as an isotope.
17a) Calculate the mass defect of the oxygen nucleus 16 8O. The mass of neutral 16 8O is equal to 15.994914 atomic mass units. Express your answer in atomic mass units to four significant figures.
Explanation / Answer
Q11)
A radioactive sample contains 1.95 g of an isotope with a half-life of 3.7 days. What mass of the isotope will remain after 5.6 days? (Assume no excretion of the nuclide from the body.) Express your answer using two significant figures.
initial mass sample = 1.95 g
Half life = 3.7 days
Mass after 5.6 days = ?
This is half life problem, so let us use the half life equation:
A = A0 * (1/2)^(t/HL)
Where A0 = initial concentration, t = time required, HL = half life and A = final concentration in time t
the 1/2 denotes that we are talking about "half life" since it is when we expect the time required to half the initial sample
So...
substitute all data
A = (1.95g)*(1/2)^(5.6 days / 3.7 days)
A =0.683001 g left after 5.6 days
this makes sense, since we expect less of the half product, since we are waiting longer time than the half reaction
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