Chapter 6, Problem 6.13QP

(a)

Interpretation Introduction

Interpretation:

An ideal gas is allowed to expand at constant temperature against atmospheric pressure.  The work is whether done on its surroundings has to be verified.

Concept introduction:

• In thermodynamics Work is defined as transfer of energy from one system to another system or system to surroundings. That is work indicates energy change.  If the change in energy carries positive sign it implies work is done on the system by the surroundings. If the change in energy carries negative sign it implies work is done by the system onto the surroundings.
• According to First law of Thermodynamics, work done is given by,

$w=-P\Delta V$

Where,

$\begin{array}{l}P=\text{ pressu}re\\ \Delta V=\text{ change in volume}\end{array}$

(b)

Interpretation Introduction

Interpretation:

An ideal gas is allowed to expand at constant temperature against atmospheric pressure.  The heat exchange between system and surroundings has to be verified.  The direction of heat change has to be ascertained.

Concept introduction:

• In thermodynamics Work is defined as transfer of energy from one system to another system or system to surroundings. That is work indicates energy change.  If the change in energy carries positive sign it implies work is done on the system by the surroundings. If the change in energy carries negative sign it implies work is done by the system onto the surroundings.
• According to First law of Thermodynamics, work done is given by,

$w=-P\Delta V$

Where,

$\begin{array}{l}P=\text{ pressu}re\\ \Delta V=\text{ change in volume}\end{array}$

(c)

Interpretation Introduction

Interpretation:

An ideal gas is allowed to expand at constant temperature against atmospheric pressure.  $\Delta U$ for the reaction has to be described.

Concept introduction:

• In thermodynamics Work is defined as transfer of energy from one system to another system or system to surroundings. That is work indicates energy change.  If the change in energy carries positive sign it implies work is done on the system by the surroundings. If the change in energy carries negative sign it implies work is done by the system onto the surroundings.
• According to First law of Thermodynamics, work done is given by,

$w=-P\Delta V$

Where,

$\begin{array}{l}P=\text{ pressu}re\\ \Delta V=\text{ change in volume}\end{array}$

• The heat content of the system is represented by ‘H’ and it is the sum of internal energy ‘U’ and product of volume and pressure,

$H=U+PV$

•  $\Delta H$ refers to change in enthalpy of the system,

$\Delta H=\Delta U+P\Delta V$