Chapter 9, Problem 17QAP

Interpretation Introduction

(a)

Interpretation:

Refer to the given phase diagram of compound X. The physical state of compound X is to be determined at pressure 35mmHg and temperature -50°C.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

The physical state of compound X is solid determined at pressure 35mmHg and temperature -50°C.

Explanation of Solution

Given Information:

The phase diagram of compound X is as follows:

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of pure substance. The phase diagram is shown below-

In the below diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

Given values-

Pressure = 35mmHg

Temperature = -50°C

These two given values are represented in the plot of the phase diagram of compound X. These two quantities are existing at the left of point B.

Hence,

At pressure 35 mmHg and at temperature -50°C, the physical state of the compound is solid.

Interpretation Introduction

(b)

Interpretation:

The normal boiling point of a compound is to be determined.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

The normal boiling point of a compound is 120°C.

Explanation of Solution

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of pure substance. The phase diagram is shown below-

In the above diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

The normal boiling temperature is the temperature at which compound start boiling which is basically atmospheric pressure. Therefore pressure for the boiling point is 760mmHg. At atmospheric pressure of boiling point, if at the particular temperature the liquid and vapor phase of a substance are at equilibrium, then that temperature is the boiling point temperature. From the phase diagram of substance at temperature, 120°C liquid and vapor phase of a substance is at the equilibrium.

Hence, the boiling point temperature is 120°C.

Interpretation Introduction

(c)

Interpretation:

The critical point for the compound is to be located.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

The critical point for the compound is located at point A.

Explanation of Solution

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of water. The phase diagram is shown below-

In the above diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

From the above diagram, the critical point of a substance is represented by the end of that curve which shows the equilibrium condition between the liquid phase and vapor phase. This curve is curved b and it ends at point A at temperature 200°C and at pressure 2 atm.

Hence, the critical point will exist at point A.

Interpretation Introduction

(d)

Interpretation:

The triple point for the compound is to be located.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

The triple point for the compound is located at point B

Explanation of Solution

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of water. The phase diagram is shown below-

In the above diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

The triple point represents the equilibrium among all the phases which are solid, liquid and gas of compound. Hence, the intersection point of all curves a, b and c will represent the triple point. From the graph, the intersection point of these three curves is existing at point B.

Therefore, point B will represent the triple point of the compound.

Interpretation Introduction

(e)

Interpretation:

The changes are to be determined at constant pressure 30mmHg and the temperature is changing from 120°C to 20°C.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

At constant pressure, 30mmHg and the process of changing of temperature from 120°C to 20°C is occurring between point D and E. In this process-

No change in phase.

The density of the vapor phase is high at point E in comparison to point D.

Explanation of Solution

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of water. The phase diagram is shown below-

In the above diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

In this process the, the pressure is constant and the temperature varies from 120°C to 20°C which is represented by point D and E. the starting point D and end point E both are existing in the vapor phase. It means there is no phase change when the temperature is decreasing form 120°C to 20°C. The density of the vapor phase at point E will be increased because it is nearer to the liquid and the solid phase in comparison to point D.

Interpretation Introduction

(f)

Interpretation:

The densest phase is to be determined.

Concept introduction:

Phase diagram can be defined as the representation of pressure and temperature quantities of any pure substance. At these values of temperature and pressure, the different phases of the pure substance are equilibrium to each other.

Answer to Problem 17QAP

The densest phase is a solid phase.

Explanation of Solution

The triple point is defined as the equilibrium condition among all the three phases of any pure substance which is solid, liquid and gas. The curves are used for the equilibrium condition between two phases of water. The phase diagram is shown below-

In the above diagram −

a = solid-liquid phase in equilibrium

b = liquid-vapor phase in equilibrium

c = solid-vapor phase in equilibrium

The densest part of this phase diagram is a solid phase because in solid phase all molecules are closely bound and from the diagram, we can see that the solid phase exists at the high temperature and low pressure, therefore, solid phase is the densest phase among all.