Chapter 3, Problem 92A

a)

Interpretation Introduction

Interpretation : The approximate boiling points for the C₂, C₄, C₆, and C₈ alkanes are to be identified.

Concept Introduction : A measure of an object's heat or cold is its temperature. The temperature of an object determines how heat is transferred.

Answer to Problem 92A

The approximate boiling points for the C₂, C₄, C₆, and C₈ alkanes are $-{100}^{\circ }\text{C}$ , $0^{\circ }\text{C}$ , ${60}^{\circ }\text{C}$ and ${125}^{\circ }\text{C}$ respectively.

Explanation of Solution

The graph is plotted between the number of carbon atoms and the boiling points.

  

With the help of a graph, the boiling point of C₂, C₄, C₆, and C₈ alkanes are obtained.

The approximate boiling point of C₂ alkane is $-{100}^{\circ }\text{C}$ .

The approximate boiling point of C₄alkane is $0^{\circ }\text{C}$ .

The approximate boiling point of C₆ alkane is ${60}^{\circ }\text{C}$ .

The approximate boiling point of C₈alkane is ${125}^{\circ }\text{C}$ .

b)

Interpretation Introduction

Interpretation : The nine alkanes that are gases at room temperature are to be identified.

Concept Introduction : A measure of an object's heat or cold is its temperature. The temperature of an object determines how heat is transferred.

Answer to Problem 92A

The alkanes that are gases at room temperature are C₁, C₂, C₃, and C₄ alkanes.

Explanation of Solution

The alkanes beyond their boiling point become gaseous.

The alkanes are liquid when it is below their boiling point.

From the graph, the alkanes that are gases at room temperature can be identified.

When the boiling point of alkanes is less than the room temperature, those alkanes become gases at that room temperature.

The alkanes such as C₁, C₂, C₃, and C₄ alkanes have less boiling point than room temperature so they become gaseous.

c)

Interpretation Introduction

Interpretation : The nine alkanes that are liquid at 350 K are to be identified.

Concept Introduction : A measure of an object's heat or cold is its temperature. The temperature of an object determines how heat is transferred.

Answer to Problem 92A

The alkanes that are liquid at 350 K are C₇, C₈, and C₉ alkanes.

Explanation of Solution

The alkanes beyond their boiling point become gaseous.

The alkanes are liquid when it is below their boiling point.

From the graph, the alkanes that are liquid at 350 K can be identified.

The temperature is 350 K means ${\text{77}}^{\text{o}}\text{C}$ according to the temperature relation ${\text{K = 273+}}^{\text{o}}\text{C}$ .

When the boiling point of alkanes is higher than 350 K, those alkanes are liquid at that temperature.

The alkanes such as C₇, C_8, and C₉ alkanes have high boiling point than 350 K so they are liquid at that temperature.

d)

Interpretation Introduction

Interpretation : The approximate increase in boiling point per additional carbon atom in these alkanes is to be identified.

Concept Introduction : A measure of an object's heat or cold is its temperature. The temperature of an object determines how heat is transferred.

Answer to Problem 92A

The approximate increase in boiling point per additional carbon atom in these alkanes is ${\text{45}}^{\text{o}}\text{C}$ .

Explanation of Solution

With the help of the graph, the approximate increase in boiling point is calculated.

There is approximately ${\text{45}}^{\text{o}}\text{C}$ increase in boiling point among the alkanes.