   # The free energy change for a reaction, Δ r G °, is the maximum energy that can be extracted from the process as work, whereas Δ r H ° is the total chemical potential energy change. The efficiency of a fuel cell is the ratio of these two quantities. Efficiency = Δ r G ° Δ r H ° × 100 % Consider the hydrogen-oxygen fuel cell, where the net reaction is H 2 ( g ) + 1 2 O 2 ( g ) → H 2 O ( l ) (a) Calculate the efficiency of the fuel cell under standard conditions. (b) Calculate the efficiency of the fuel cell if the product is water vapor instead of liquid water. (c) Does the efficiency depend on the state of the reaction product? Why or why not? ### Chemistry & Chemical Reactivity

9th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781133949640

#### Solutions

Chapter
Section ### Chemistry & Chemical Reactivity

9th Edition
John C. Kotz + 3 others
Publisher: Cengage Learning
ISBN: 9781133949640
Chapter 19, Problem 106SCQ
Textbook Problem
1 views

## The free energy change for a reaction, ΔrG°, is the maximum energy that can be extracted from the process as work, whereas ΔrH° is the total chemical potential energy change. The efficiency of a fuel cell is the ratio of these two quantities. Efficiency =  Δ r G ° Δ r H ° × 100 % Consider the hydrogen-oxygen fuel cell, where the net reaction is H 2 ( g )  +  1 2  O 2 ( g ) →  H 2 O ( l ) (a) Calculate the efficiency of the fuel cell under standard conditions. (b) Calculate the efficiency of the fuel cell if the product is water vapor instead of liquid water. (c) Does the efficiency depend on the state of the reaction product? Why or why not?

(a)

Interpretation Introduction

Interpretation:

The efficiency of fuel cell under standard conditions has to be determined.

Concept introduction:

The free energy change for a reaction  ΔrGo is a thermodynamic potential that can be used to calculate maximum reversible work. The system is held at constant temperature and pressure and is closed.

The heat evolved or absorbed when a reaction takes place at a constant pressure under the standard condition is called standard enthalpy change, ΔrHo of the reaction.

The efficiency of a fuel cell is given as,

Efficiency=ΔrGΔrH×100%

### Explanation of Solution

The efficiency of the fuel cell under standard conditions is calculated below.

Given:

The hydrogen-oxygen fuel cell reaction is written as,

H2(g)+12O2(g)H2O(l)

Refer to the appendix L for the values of ΔrGo and ΔrHo.

The ΔrHo for liquid water is 285.83kJmol1.

The ΔrGo for liquid water is 237.15kJmol1

(b)

Interpretation Introduction

Interpretation:

The efficiency of a fuel cell if the product is water vapour instead of liquid water has to be determined.

Concept introduction:

The free energy change for a reaction  ΔrGo is a thermodynamic potential that can be used to calculate maximum reversible work. The system is held at constant temperature and pressure and is closed.

The heat evolved or absorbed when a reaction takes place at a constant pressure under the standard condition is called standard enthalpy change, ΔrHo of the reaction.

The efficiency of a fuel cell is given as,

Efficiency=ΔrGΔrH×100%

(c)

Interpretation Introduction

Interpretation:

The efficiency whether depends upon the reaction product or not has to be stated.

Concept introduction:

The free energy change for a reaction  ΔrGo is a thermodynamic potential that can be used to calculate maximum reversible work. The system is held at constant temperature and pressure and is closed.

The heat evolved or absorbed when a reaction takes place at a constant pressure under the standard condition is called standard enthalpy change, ΔrHo of the reaction.

The efficiency of a fuel cell is given as,

Efficiency=ΔrGΔrH×100%

### Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

#### The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started

Find more solutions based on key concepts
Saturation refers to the ability of a fat to penetrate a barrier, such as paper. whether or not a fatty acid ch...

Nutrition: Concepts and Controversies - Standalone book (MindTap Course List)

How can errors in the cell cycle lead to cancer in humans?

Human Heredity: Principles and Issues (MindTap Course List)

Assign IUPAC names to the following alcohols: a. CH3CH2CH2OH b. c. d. e. f.

Chemistry for Today: General, Organic, and Biochemistry

How did echo sounding and an understanding of radiometric dating influence the debate?

Oceanography: An Invitation To Marine Science, Loose-leaf Versin

Submarine A travels horizontally at 11.0 m/s through ocean water. It emits a sonar signal of frequency f = 5.27...

Physics for Scientists and Engineers, Technology Update (No access codes included)

Convert the following distances into SI units. Which is larger? d1 = 1.02 km d2 = 102 105 Mm

Physics for Scientists and Engineers: Foundations and Connections 