Chapter 10, Problem 14A

(a)

Interpretation Introduction

Interpretation: The process needs to be identified as exothermic or endothermic when solid KBr is dissolved in water, it gets colder.

Concept Introduction: On the basis of energy change during the chemical reaction, they can be classified as endothermic and exothermic reactions.

An exothermic reaction can be defined as the chemical reactions in which the energy is released whereas in an endothermic reaction, reaction proceeds with absorption of energy.

Answer to Problem 14A

It is an endothermic reaction.

Explanation of Solution

When solid KBr is dissolved in water, the solution gets colder. It means the temperature decreases during dissolution of solid KBr. It proves that the reaction must proceed with absorption of energy in the form of heat. Thus it is an endothermic reaction.

(b)

Interpretation Introduction

Interpretation: The burning of natural gas in a furnace needs to be identified as exothermic or endothermic process.

Concept Introduction: On the basis of energy change during the chemical reaction, they can be classified as endothermic and exothermic reactions.

An exothermic reaction can be defined as the chemical reactions in which the energy is released whereas in an endothermic reaction, reaction proceeds with absorption of energy.

Answer to Problem 14A

It is an exothermic reaction.

Explanation of Solution

The burning of natural gas in furnace must be an exothermic process because it releases certain amount of energy in the form of heat and light.

Burning or combustion is always an exothermic process as it always releases energy in the form of heat.

(c)

Interpretation Introduction

Interpretation: The dissolution of concentrated sulphuric acid in water needs to be identified as an exothermic or endothermic process.

Concept Introduction: On the basis of energy change during the chemical reaction, they can be classified as endothermic and exothermic reactions.

An exothermic reaction can be defined as the chemical reactions in which the energy is released whereas in an endothermic reaction, reaction proceeds with absorption of energy.

Answer to Problem 14A

It is an exothermic reaction.

Explanation of Solution

When concentrated sulphuric acid is added to water, the solution becomes very hot. It proves that energy is released in heat which increases the temperature of solution. Thus it must be an exothermic reaction.

(d)

Interpretation Introduction

Interpretation: The boiling of water in a tea kettle needs to be classified as an exothermic or endothermic process.

Concept Introduction: On the basis of energy change during the chemical reaction, they can be classified as endothermic and exothermic reactions.

An exothermic reaction can be defined as the chemical reactions in which the energy is released whereas in an endothermic reaction, reaction proceeds with absorption of energy.

Answer to Problem 14A

The boiling of water is an endothermic reaction.

Explanation of Solution

The boiling of water turns it to water vapour. The water molecules absorbs energy in the form of heat and change to gaseous state.

Thus it should be endothermic process as heat is absorbed during the process.