1-The half-life of cesium-129 is 32.0 hours . How much time is required for the

Question

1-The half-life of cesium-129 is 32.0 hours. How much time is required for the activity of a sample of cesium-129 to fall to 16.6 percent of its original value?

hrs

B)Chromium-51 is a radioisotope that is used to assess the lifetime of red blood cells The half-life of chromium-51 is 27.7 days. If you begin with 34.4 mg of this isotope, what mass remains after 54.0 days have passed?

mg

C)What is the binding energy in kJ/mol La for lanthanum-139?    kJ/mol

d)What is the binding energy in kJ/mol In for indium-113?    kJ/mol

2-

mg

Explanation / Answer

1.

k = 0.693 / t1/2

k = 0.693 / 32.0

k = 0.0216 h-1

First order integrated rate consant equation is,

k = ( 1 / t ) * ln([A]0 / [A]t)

0.0216 = ( 1 / t ) * ln(100 / 16.6)

t = 83.1 h

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