The radioactive nuclide 199Pt has a half life of 30.8 minutes. A sample is prepared that has an initial activity of 7.56x1011Bq. (a) How many 199Pt nuclei are initially present in the sample? (b) How many are present after 30.8minutes? What is the activity at this time? (c) Repeat part (b) for a time 92.4 minutes after the sample is first prepared.
(a) 2.02x1015, (b) 1.01x1015, 3.78x1011Bq, (c) 2.52x1014, 9.45x1010Bq Q2. The unstable isotope 40K is used for dating of rock samples. Its half life is 1.28x109 years. (a) How many decays occur per second in a sample containing 1.63x10-6g of 40K? (b) What is the activity of the sample in curies? 0.421Bq , 1.14x10-11Ci
The most common (99.3%) isotope of Uranium, 238U, has a half life of 4.47x109 years, decaying to 234Th by α emission. (a) What is the decay constant? (b) What mass of uranium would be required for an activity of 12.0μCi? (c) How many α particles are emitted per second by 60.0g of 238U? -18 -1 (a) 4.91x10 s , (b) 35.7g, (c) 7.46x105 Q4. Consider the nuclear reaction 2 9 X + 4 He where X is a nuclide. 1 H + 4 Be 2 (a) What are the values of Z and A for the nuclide X? (b) How much energy is liberated? (c) Estimate the threshold energy for this reaction. (a) Z=3, A=7, (b) 7.151MeV, (c) 1.4MeV Q5. Consider the nuclear reaction 2 1
H + 14 N 7
X +10 B 5
where X is a nuclide. (a) What are Z and A for the nuclide X? (b) Calculate the reaction energy Q (in MeV). (c) If the 2 H nucleus is incident on a stationary 1 must it have for the reaction to occur? (a) Z=3, A=6, (b) -10.14MeV, (c) 11.60MeV Q6. A 235 92
N , what minimum kinetic energy
U nucleus at rest absorbs a low-energy neutron. What is the internal excitation 236 92
energy of the
U * nucleus that is produced? The atomic masses of the neutral atoms in 235 92
their nuclear ground states are 235.043923u for (a)...