Chapter 10, Problem 10B.4E

(a)

Interpretation Introduction

Interpretation:

The number of atoms of Cobalt-60 present in the sample has to be given.

Concept Introduction:

The relation between the rate of decay and the number N of radioactive nuclei present is given by the law of radioactive decay

  $\text{Activity=}\text{k×N}$

Where,

N is the number of atoms in the sample.

(b)

Interpretation Introduction

Interpretation:

The mass of the sample in terms of grams has to be given.

Concept Introduction:

The mass of the sample is calculated by using the below formula,

  $\frac{\text{No}\text{of}\text{atoms}}{\text{1}}\text{×}\frac{\text{1}\text{mol}}{{\text{N}}_{\text{A}}}\text{×}\frac{\text{No}\text{of}\text{gram}}{\text{mol}}$

Where,

${\text{N}}_{\text{A}}$ is the Avogadro number ($\text{6}{\text{.022×10}}^{\text{23}}\text{}\text{atoms}$).