Half-life Problems Exam with
100% correct answers already
graded A+
An isotope of Cesium (Cesium-137) has a half-life of 30 years. If 1.0
mg of Cesium-137 disintegrates over a period of 90 years, how
many mg of Cesium-137 remain? - answer 0.125 mg
A 2.5 gram sample of an isotope of Strontium-90 was formed in a
1960 explosion of an atomic bomb at Johnson island in the Pacific
Test Site. The half-life of Strontium-90 is 28 years. In what year will
only 0.625 grams of this Strontium-90 remain? - answer 56 years
Actinium-226 has a half-life of 29 hours. If 100 mg of Actinium-226
disintegrates over a period of 58 hours, how many mg of Actinium-
226 will remain? - answer 25 mg
Thallium-201 has a half-life of 73 hours. If 4.0 mg of Thallium-201
disintegrates over a a period of 6 days and 2 hours, how many mg of
Thallium-201 will remain? - answer 1 mg
Sodium-25 was to be used in an experiment, but it took 3 minutes to
get the Sodium from the reactor to the laboratory. If 5.0 mg of
Sodium-25 was removed from the reactor, how many mg of Sodium-
25 were placed in the reaction vessel 3 minutes later if the half-life
of Sodium-25 is 60 seconds? - answer 0.625 mg
The half-life of isotope X is 2 years. How many years would it take
for a 4.0 mg sample of isotope X to decay and only have 0.50 mg of
it remain? - answer 6 years
100% correct answers already
graded A+
An isotope of Cesium (Cesium-137) has a half-life of 30 years. If 1.0
mg of Cesium-137 disintegrates over a period of 90 years, how
many mg of Cesium-137 remain? - answer 0.125 mg
A 2.5 gram sample of an isotope of Strontium-90 was formed in a
1960 explosion of an atomic bomb at Johnson island in the Pacific
Test Site. The half-life of Strontium-90 is 28 years. In what year will
only 0.625 grams of this Strontium-90 remain? - answer 56 years
Actinium-226 has a half-life of 29 hours. If 100 mg of Actinium-226
disintegrates over a period of 58 hours, how many mg of Actinium-
226 will remain? - answer 25 mg
Thallium-201 has a half-life of 73 hours. If 4.0 mg of Thallium-201
disintegrates over a a period of 6 days and 2 hours, how many mg of
Thallium-201 will remain? - answer 1 mg
Sodium-25 was to be used in an experiment, but it took 3 minutes to
get the Sodium from the reactor to the laboratory. If 5.0 mg of
Sodium-25 was removed from the reactor, how many mg of Sodium-
25 were placed in the reaction vessel 3 minutes later if the half-life
of Sodium-25 is 60 seconds? - answer 0.625 mg
The half-life of isotope X is 2 years. How many years would it take
for a 4.0 mg sample of isotope X to decay and only have 0.50 mg of
it remain? - answer 6 years
