Calculate the age (in years) of a rock sample if 75.0 percent of the original amount
of thorium-232 (232Th) contained in the rock has undergone radioactive decay?
The half-life for 232Th is 1.4 x 1010 yrs.
(a) 5.8 x 109 years
(b) 7.0 x 109 years
(c) 2.1 x 1010 years
,(d) 2.8 x 1010 years
(e) 3.5 x 1010 years - ✔✔(d) 2.8 x 1010 years
Naturally-occurring uranium contains 0.005% 234U, 0.720% 235U and 99.275%
238U. In order to be used as fuel in a fission power plant, the uranium must be
enriched to contain about 3% 235U. This is necessary because
(a) 238U undergoes fission too easily.
(b) the amount of 235U in naturally-occurring uranium is too low to sustain
fission.
(c) 235U also functions as the moderator.
(d) 235U reduces the number of neutrons colliding with the fuel thereby
controlling the chain reactions. - ✔✔(b) the amount of 235U in
naturally-occurring uranium is too low to sustain fission.
Unobtainium (Ub), a fictional element mined on Pandora (Avatar), undergoes the
following fission reaction after neutron capture. What are the atomic and mass
numbers of Unobtainium (Ub)? Ub + n 0 1 → I 53 105 + La 57 146 + 3 n 0 1
, (a) 108 and 251
(b) 112 and 253
(c) 110 and 251
(d) 110 and 253
(e) 110 and 254 - ✔✔(d) 110 and 253
Sodium-23 (23Na) is formed by the β+ decay of which one of the following
isotopes?
(a) Mg 12 23
(b) Mg 12 24
(c) Mg 12 22
(d) Ne 10 22
(e) Ne 10 23 - ✔✔(a) Mg 12 23
Which one of the following nuclides would you predict to be most stable?
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