Chapter 11, Problem 11.34EP

(a)

Interpretation Introduction

Interpretation:

Quantity of Sr-90 that will be present after 84 years has to be calculated if the initial quantity taken was 8.00 g and half-life of Sr-90 is 28 years.

Concept Introduction:

Radioactive nuclides undergo disintegration by emission of radiation.  All the radioactive nuclide do not undergo the decay at a same rate.  Some decay rapidly and others decay very slowly.  The nuclear stability can be quantitatively expressed by using the half-life.

The time required for half quantity of the radioactive substance to undergo decay is known as half-life.  It is represented as $t_{1/2}$.

The equation that relates amount of decayed radioactive material, amount of undecayed radioactive material and the time elapsed can be given as,

$\left(\begin{array}{l}\text{Amount}\text{of}\text{radionuclide}\\ \text{undecayed}\text{after}n\text{half}\text{lives}\end{array}\right)\text{= }\left(\begin{array}{l}\text{Original}\text{amount}\\ \text{of}\text{radionuclide}\end{array}\right)\text{ x }\left(\frac{\text{1}}{{\text{2}}^n}\right)$

(b)

Interpretation Introduction

Interpretation:

Time taken to reduce 80.0 mg sample of Sr-90 to 10.0 mg has to be calculated if the half-life of Sr-90 is 28 years.

Concept Introduction:

Radioactive nuclides undergo disintegration by emission of radiation.  All the radioactive nuclide do not undergo the decay at a same rate.  Some decay rapidly and others decay very slowly.  The nuclear stability can be quantitatively expressed by using the half-life.

The time required for half quantity of the radioactive substance to undergo decay is known as half-life.  It is represented as $t_{1/2}$.

The equation that relates amount of decayed radioactive material, amount of undecayed radioactive material and the time elapsed can be given as,

$\left(\begin{array}{l}\text{Amount}\text{of}\text{radionuclide}\\ \text{undecayed}\text{after}n\text{half}\text{lives}\end{array}\right)\text{= }\left(\begin{array}{l}\text{Original}\text{amount}\\ \text{of}\text{radionuclide}\end{array}\right)\text{ x }\left(\frac{\text{1}}{{\text{2}}^n}\right)$