Question 1

Which equation represents the Gibbs Phase Rule for a general system?

Accepted Answer

$$F = C - P + 2$$

Question 2

In a one-component system, how many degrees of freedom are present at the triple point?

Accepted Answer

$$F = 0$$

Question 3

Why is it impossible to have four phases in mutual equilibrium in a one-component system?

Accepted Answer

Because $$F$$ would be negative, which is not physically meaningful.

Question 4

At the boundary between liquid and vapor in a one-component system, how many intensive variables can be changed independently?

Accepted Answer

One

Question 5

Which of the following best describes the critical point on a phase diagram?

Accepted Answer

The highest temperature and pressure at which a liquid and vapor can coexist

Question 6

For pure water, what is the maximum number of intensive variables that can be independently varied in a single-phase region?

Accepted Answer

Two

Question 7

Why does solid CO$$_2 ($$dry ice) sublime at 1 atm instead of melting?

Accepted Answer

Because the triple point pressure of CO$$_2 is $$higher than 1 atm

Question 8

Which of the following statements about the phase diagram of water is correct?

Accepted Answer

The melting point of ice decreases with increasing pressure

Question 9

On Venus, the surface pressure and temperature are above the critical point of CO$$_2. $$What phase is CO$$_2 in $$under these conditions?

Accepted Answer

Supercritical fluid

Question 10

A chemist wants to synthesize diamonds from graphite. According to the phase diagram of carbon, what conditions are required?

Accepted Answer

High temperature and high pressure

Question 11

If a one-component system is in equilibrium with two phases, what is the formula for the degrees of freedom?

Accepted Answer

$$F = 3 - P$$

Question 12

Which real-world application relies on the properties of supercritical CO$$_2$$?

Accepted Answer

Extraction of caffeine from coffee beans

Question 13

What does the area inside a single region (not on a line or point) of a phase diagram represent?

Accepted Answer

A single phase of the substance

Question 14

Which variable(s) must be fixed to maintain equilibrium at the triple point of a one-component system?

Accepted Answer

Both temperature and pressure

Question 15

If the number of components $$C is 2 $$and the number of phases $$P is 3$$, what is the number of degrees of freedom $$F$$?

Accepted Answer

$$F = 1$$

Question 16

Which of the following best explains why phase diagrams do not provide kinetic information?

Accepted Answer

They only show equilibrium states, not the rates of phase changes.

Question 17

A sample of water is at 1 atm and 100$$^\circC. $$Which phase(s) are present?

Accepted Answer

Liquid and vapor in equilibrium

Question 18

Which of the following is a correct interpretation of the degrees of freedom in the Gibbs Phase Rule?

Accepted Answer

The number of intensive variables that can be changed without altering the number of phases in equilibrium.

Question 19

In the context of the phase rule, what is meant by a 'component'?

Accepted Answer

A chemically independent constituent of the system.

Question 20

Which of the following best describes the significance of the triple point in a phase diagram?

Accepted Answer

It is the only condition where all three phases can coexist in equilibrium.

Phase Equilibria and the Gibbs Phase Rule in One-Component Systems

Study Guide - Practice Questions