Textbook Question
The half-life of 232Th is 1.4⨉1010 yr. Find the number of disintegrations per hour emitted by 1.0 mol of 232Th.
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Ch.20 - Radioactivity and Nuclear Chemistry
Chapter 20, Problem 95
When a positron and an electron collide and annihilate each other, two photons of equal energy are produced. What is the wavelength of these photons?
Verified step by step guidance1
Understand that when a positron and an electron annihilate, their mass is converted into energy in the form of photons.
Use the equation for energy-mass equivalence, $E = mc^2$, to calculate the total energy released, where $m$ is the mass of the electron (or positron) and $c$ is the speed of light.
Since two photons are produced, divide the total energy by 2 to find the energy of each photon.
Use the equation for the energy of a photon, $E = \frac{hc}{\lambda}$, where $h$ is Planck's constant and $\lambda$ is the wavelength, to solve for the wavelength of each photon.
Rearrange the equation to solve for $\lambda$: $\lambda = \frac{hc}{E}$, and substitute the known values to find the wavelength.
Related Practice
Open Question
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A 228-mL sample of an aqueous solution contains 2.35% MgCl2 by mass. Exactly one-half of the magnesium ions are Mg-28, a beta emitter with a half-life of 21 hours. What is the decay rate of Mg-28 in the solution after 4.00 days? (Assume a density of 1.02 g/mL for the solution.)
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The half-life of 235U, an alpha emitter, is 7.1⨉108 years. Calculate the number of alpha particles emitted by 1.0 mg of this nuclide in 1.0 minute.
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Given that the energy released in the fusion of two deuterons to a 3He and a neutron is 3.3 MeV, and in the fusion to tritium and a proton it is 4.0 MeV, calculate the energy change for the process 3He + 1n → 3H + 1p. Suggest an explanation for why this process occurs at much lower temperatures than either of the first two.
Textbook Question
The nuclide 18F decays by both electron capture and β+ decay. Find the difference in the energy released by these two processes. The atomic masses are 18F = 18.000950 and 18O = 17.9991598.
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