Chapter 8, Problem 97SCQ

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074

Chapter
Section

### Chemistry & Chemical Reactivity

10th Edition
John C. Kotz + 3 others
ISBN: 9781337399074
Textbook Problem

# Bromine-containing species play a role in environmental chemistry. For example, they are evolved in volcanic eruptions. (a) The following molecules are important in bromine environmental chemistry: HBr, BrO, and HOBr. Which is an odd-electron molecule? (b) Use bond dissociation enthalpies to estimate Δ r H for three reactions of bromine: Br2(g) → 2 Br(g) 2 Br(g) + O2(g) → 2 BrO(g) BrO(g) + H2O(g) → HOBr(g) + OH(g) (c) Using bond dissociation enthalpies, estimate the standard enthalpy of formation of HOBr(g) from H2(g), O2(g), and Br2(g). (d) Are the reactions in parts (b) and (c) exothermic or endothermic?

(a)

Interpretation Introduction

Interpretation:

An odd electron molecule from the given list has to be determined.

Concept Introduction:

In a balanced equation the number of atoms of each element as a reactant is equal to the number of atoms of that element as a product.

Coefficient is a number placed before a formula in a chemical equation.

A balanced equation should be obeying the law of conservation of mass. Law of conservation of mass states that, the number of atoms remains constant throughout the reaction, simply it can be stated as follows, “during a chemical reaction atoms are neither be created nor be destroyed”.

Explanation

Given molecules are:

HBr,BrOâ€‰andâ€‰HOBr

HBr have 8 electrons.

BrO have 13 electrons

(b)

Interpretation Introduction

Interpretation:

The enthalpy changes of the given reactions have to be determined.

Concept Introduction:

Bond energy or more correctly the bond dissociation enthalpy is the enthalpy change when breaking a bond in a molecule with the reactant and products in the gas phase.

ΔrH=ΔH(bondsbroken)ΔH(bondsformed)

Enthalpy of formation:

ΔrH=ΔfH0(products)ΔfH0(reactants)

(c)

Interpretation Introduction

Interpretation:

The enthalpy change of the formation of HOBr has to be determined.

Concept Introduction:

Bond energy or more correctly the bond dissociation enthalpy is the enthalpy change when breaking a bond in a molecule with the reactant and products in the gas phase.

ΔrH=ΔH(bondsbroken)ΔH(bondsformed)

Enthalpy of formation:

ΔrH=ΔfH0(products)ΔfH0(reactants)

(d)

Interpretation Introduction

Interpretation:

The reactions which are endothermic or exothermic have to be identified.

Concept Introduction:

Bond energy or more correctly the bond dissociation enthalpy is the enthalpy change when breaking a bond in a molecule with the reactant and products in the gas phase.

ΔrH=ΔH(bondsbroken)ΔH(bondsformed)

Enthalpy of formation:

ΔrH=ΔfH0(products)ΔfH0(reactants)

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