Chapter 16, Problem 38CI

(a)

Interpretation Introduction

Interpretation: K-40 has a natural abundance of 0.012% and a half-life of 1.30 x 10⁹yr. K-40 decays to Ca-40 or to Ar-40. Activity for K-40 is 7.0 µCi per gm.

To write a balanced nuclear equation for each type of decay

Concept Introduction: According to the law of conservation of mass the sum of the atomic numbers and the sum of the atomic mases on the reactant side must be equal to the product side.

(b)

Interpretation Introduction

Interpretation: K-40 has a natural abundance of 0.012% and a half-life of 1.30 x 10⁹yr. K-40 decays to Ca-40 or to Ar-40. Activity for K-40 is 7.0 µCi per gm.

To identify the particle emitted for each type of decay.

Concept Introduction:Radioactive decay is the process by which an unstable atomic nucleus loses energy by emitting radiation, such as an alpha particle, beta particle with neutrino.

(c)

Interpretation Introduction

Interpretation: K-40 has a natural abundance of 0.012% and a half-life of 1.30 x 10⁹yr. K-40 decays to Ca-40 or to Ar-40. Activity for K-40 is 7.0 µCi per gm.

To find the number of K+ ions in 3.5 oz of KCl

Concept Introduction:From the mass and molar mass of a substance, number of moles can be calculated as follows:

  $\text{Moles = }\frac{\text{mass}}{\text{molar}\text{mass}}$

(d)

Interpretation Introduction

Interpretation: K-40 has a natural abundance of 0.012% and a half-life of 1.30 x 10⁹yr. K-40 decays to Ca-40 or to Ar-40. Activity for K-40 is 7.0 µCi per gm.

To find the activity of 25g of KCl in becquerels

Concept Introduction:

An arithmetical multiplier which is used for converting a quantity expressed in one unit into another equivalent set of units is said to be conversion factor.

The conversion factor used to convert curie to becquerel is as follows:

  $\text{1 curie }=\text{ 37}\times {\text{10}}^{\text{9}}\text{ becquerel}$