Chapter 20, Problem 1E

(a)

Interpretation Introduction

Interpretation:

The term thermal stability needs to be described.

Concept Introduction:

If heat is applied to fluid, it has tendency to breakdown due to stress on it but if the fluid is able to resist its breaking down, then it is said to have thermal stability.

Answer to Problem 1E

The thermal stability is termed as the ability of the liquid or fluid to be able to resist its breakdown due that is caused by the heat stress.

Explanation of Solution

Each molecule has its own structure which decides its strength based on the bonding of the molecules. It’s the bonds between the molecules which determine the stability of the molecule against thermal stress. For instance, considering the group 1, it is noticed that nitrates get stable on going down the group and decomposition of nitrates requires high energy. In other words, higher temperature is necessary to break the bonds for the dissociation of N-O bonds of the nitrate anions.

(b)

Interpretation Introduction

Interpretation:

The term kinetic stability needs to be defined.

Concept Introduction:

For reaction to take place, though it is thermodynamically stable, there are certain kinetic limitation that hinders it. In other words, energy changes needs to be favorable for reaction to take place.

Answer to Problem 1E

If the reactants do not react spontaneously but rather slowly, then the reaction is said to be kinetically stable.

Explanation of Solution

A reaction is said to have kinetic stability if the reactants reacts very slowly indicating that more slowly it is the higher is its kinetic stability. It is also said that the bonds do not break quickly as the there is co-existence of the particles without collisions as there is not enough energy for the reaction to take place. Thereby it also indicates that activation energy is high. Thereby the reaction is kinetically stable.

(c)

Interpretation Introduction

Interpretation:

The term radioactive decay needs to be defined.

Concept Introduction: When there is spontaneous breakdown of an unstable atomic nucleus, it causes fragmentation of the nucleus to smaller fragments which are stable structures. Instability within the nucleus is caused by imbalance of the number of protons and neutrons.

Answer to Problem 1E

Unstable atomic nucleus when undergoes breakdown, it dissociates to smaller fragments releasing energy in the form of radiation. This process is termed as radioactive decay.

Explanation of Solution

When an unstable nucleus wants to get to its stable state, it dissociates to give smaller nucleus, which is a new element, having stable structure and energy in the form of radiation. This process takes place spontaneously and is termed as radioactive decay. As the binding energy of that unstable nucleus is not strong enough, it can be easily broken down.

(d)

Interpretation Introduction

Interpretation:

The term β- particle production needs to be defined.

Concept Introduction:

Decay of radioactive nucleus leads to emission of different particles which are alpha, beta and gamma. The alpha particles are He-4 nuclei, beta is electrons and gamma rays are electromagnetic rays.

Answer to Problem 1E

The β- particle are produced from decay of radioactive nucleus which has too many protons or too many neutrons.

Explanation of Solution

The decay of radioactive nucleus emits β- particle which are smaller than alpha particles and is having less ionizing power. The β- particle emitted is high energy electron and is symbolized as $e$ . When beta particle is emitted, there is no change in mass number but causes atomic number to increase by 1.

Example is $C\to e+N$

(e)

Interpretation Introduction

Interpretation:

The term a- particle production needs to be explained.

Concept Introduction:

When a radioactive nucleus decays there is emission of different particles namely alpha, beta and gamma. The alpha particles are He-4 nuclei, beta is electrons and gamma rays are electromagnetic rays.

Answer to Problem 1E

The- particle are produced from decay of radioactive nucleus. It has two protons and two neutrons. Mostly Uranium -238 and Throium-230 are main producers of a- particles.

Explanation of Solution

The decay of a radioactive nucleus emits a- particle happens if the nuclei have a very large proton to neutron ratio. By the emission of this particle, the nuclei will get a reduced ratio of proton to neutron. It is often symbolized as $He$ .

Example is $U\to Th+He$

(f)

Interpretation Introduction

Interpretation:

The term positron production needs to be explained.

Concept Introduction:

During the decay of radioactive nucleus, certain particles are emitted which are alpha, beta and gamma. The alpha particles are He-4 nuclei, beta is electrons and gamma rays are electromagnetic rays.

Answer to Problem 1E

The positron is the antiparticle of proton and is emitted when there is beta plus decay wherein the proton dissociates to a neutron, positron and neutrino

Explanation of Solution

When there are too many neutrons or protons in nucleus, it gets transformed into one form releasing a more stable nucleus. This process is the beta decay. When there is excess proton, it gets transformed in to a neutron, releasing positron and neutrino and depicted as $p\to n+e^{+}+\nu$  

(g)

Interpretation Introduction

Interpretation:

The term electron capture needs to be explained.

Concept Introduction:

The process wherein the unstable atoms become more stable is said to be electron capture. In this, the electrons from an atoms inner shell are taken into the nucleus in which it combines with proton to form neutron and neutrino.

Answer to Problem 1E

The electron capture process involves the absorption of atomic electron to nuclei which is proton rich which transforms proton to neutron releasing neutrino.

Explanation of Solution

When an electron of low energy inner orbital comes too close to a proton, it gets captured and converts releasing neutron and neutrino. Here the unstable atoms get converted to stable form wherein the nuclear protons changes to neutrons and releases neutrino. In this process, the inner shell atoms are drawn towards the nucleus thus bringing about this combination.

(h)

Interpretation Introduction

Interpretation:

The term γ-ray emissions needs to be explained.

Concept Introduction:

The decay of radioactive nucleus causes emission of certain particles like alpha, beta and gamma. The alpha particles are He-4 nuclei, beta is electrons and gamma rays are electromagnetic rays.

Answer to Problem 1E

When the radioactive atomic nuclei disintegrates or decays, it causes release of new daughter nucleus which is stable and gamma radiations.

Explanation of Solution

The decay of unstable radioactive nuclei causes the release of stable nuclei and gamma rays. The emission of gamma rays does not cause any changes to the number of protons or neutrons. Instead it is only the effects of nucleus moving from higher energy state to lower energy state. It usually is associated with alpha, and beta decays.