Chapter 18, Problem 4STP

(a)

Interpretation Introduction

Interpretation: Whether the reaction is spontaneous at a relatively low temperature or at a relatively high temperature is to be stated.

  ${\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)$

Concept Introduction: A reaction that favors the formation of the products naturally under the given conditions is called a spontaneous reaction.

Answer to Problem 4STP

The reaction is spontaneous at relatively low temperatures.

Explanation of Solution

At high temperatures, the reaction will be spontaneous when both the change in enthalpy and entropy are positive.

At low temperatures, the reaction will be spontaneous when both the change in enthalpy and entropy are negative.

In the given reaction ${\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)$ , water changes from liquid to gaseous state which means the disorders in the system are increasing; therefore, the reaction is spontaneous at a relatively low temperature.

(b)

Interpretation Introduction

Interpretation: Whether the reaction is spontaneous at a relatively low temperature or relatively high temperature is to be stated.

  ${\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Concept Introduction: A reaction that favors the formation of the products naturally under the given conditions is called a spontaneous reaction.

Answer to Problem 4STP

The reaction is spontaneous at relatively high temperatures.

Explanation of Solution

In the given reaction ${\text{H}}_{\text{2}}\text{O}\left(\text{g}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$ , water changes from a gaseous to a liquid state, which means the disorderness in the system is decreasing; therefore, for the reaction to be spontaneous, a high temperature is needed. Thus, the reaction is spontaneous at relatively high temperatures.

(c)

Interpretation Introduction

Interpretation: Whether the reaction is spontaneous at a relatively low temperature or relatively high temperature is to be stated.

  ${\text{H}}_{\text{2}}\text{O}\left(\text{s}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$

Concept Introduction: A reaction that favors the formation of the products naturally under the given conditions is called a spontaneous reaction.

Answer to Problem 4STP

The reaction is spontaneous at relatively high temperatures.

Explanation of Solution

In the given reaction ${\text{H}}_{\text{2}}\text{O}\left(\text{s}\right)\to {\text{H}}_{\text{2}}\text{O}\left(\text{l}\right)$ , water is changing from a gaseous to a liquid state which means the disorderness in the system but the change in enthalpy for this process outweighs entropy. Thus, the reaction is spontaneous at relatively high temperatures.