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Chapter 12: Q3. (page 398)

If there is 10 μmol of the radioactive isotope ³²P (half-life 14 days) at t=0, how much will ³²P remain at (a) 7 days, (b) 14 days, (c) 21 days,
and (d) 70 days?

Short Answer

Expert verified
  1. The quantity of ³²P that will remain after 7 days is 7.04 μmol.
  2. The quantity of ³²P that will remain after 14 days is 4.96μmol.
  3. The quantity of ³²P that will remain after 21 days is 3.49μmol.
  4. The quantity of ³²P that will remain after 70 days is 0.3μmol.

Step by step solution

01

Half-life

The time it takes for a substance's concentration to drop to half of its starting value is known as the half-life period. The reaction's starting concentration has no bearing on the reaction's half-life.

02

Explanation for (a)

The half-life of ³²P is 7 days.

The expression used to calculate the concentration of radioactive isotope at half-life is:

A=Ae- kt

Now,

t1/2=0.693kk=0,693t12k=0.05days-1

On substituting the value of k and t in the expression,

A=Ae-kt        =10×e-0.35        =7.04μ mol

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