Free Practice Quiz Question List

11/14 Thermodynamics and Chemical Spontaneity Online Quiz Questions

Use this free practice quiz with 20 questions to review 11/14 Thermodynamics and Chemical Spontaneity, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

Which statement best distinguishes spontaneity from reaction rate?

A
A spontaneous process must occur rapidly.
B
A spontaneous process may be extremely slow.
C
A spontaneous process always requires continuous external energy.
D
A spontaneous process can occur only at equilibrium.

True or false

1 point

According to the second law of thermodynamics, a spontaneous process under specified conditions has $\Delta S_{\text{univ}}>0$ .

A
True
B
False

Choose all

1 point

Select all processes that generally increase entropy.

A
A liquid freezes to form a solid.
B
A solid melts to form a liquid.
C
A liquid vaporizes to form a gas.
D
A solute dissolves and becomes dispersed.
E
A gas condenses to form a liquid.

Written response

1 point

Enter the equation that relates the Gibbs energy change, enthalpy change, entropy change, and absolute temperature at constant temperature and pressure.

Fill in the blank

1 point

At constant temperature and pressure, a process with $\Delta G$ is in the forward direction.

Choose one

1 point

A process has $\Delta H<0$ and $\Delta S<0$ . Assuming these values remain approximately constant, when is the process expected to be spontaneous?

A
Spontaneous only at sufficiently high temperature
B
Spontaneous at all temperatures
C
Spontaneous at sufficiently low temperature
D
Nonspontaneous at all temperatures

Written response

1 point

A process has ΔH = +25.0 kJ mol⁻¹ and ΔS = +80.0 J mol⁻¹ K⁻¹. At what temperature is ΔG = 0? Enter the numerical temperature in kelvins, rounded to three significant figures.

Open ended

1 point

At 298 K, a reaction has $\Delta H^\circ=-92.0\ \mathrm{kJ\,mol^{-1}}$ and $\Delta S^\circ=-198\ \mathrm{J\,mol^{-1}\,K^{-1}}$ . Calculate $\Delta G^\circ$ , show the necessary unit conversion, and state whether the forward reaction is spontaneous under standard conditions.

Choose all

1 point

Select all statements that correctly describe the reaction quotient $Q$ .

A
Activities are raised to powers given by stoichiometric coefficients.
B
Concentrations or partial pressures may approximate activities in introductory calculations.
C
Pure solids must always be included in the reaction quotient.
D
Pure liquids are omitted because their activities are approximately constant.
E
The reaction quotient is independent of the actual conditions.

True or false

1 point

At equilibrium, the reaction quotient equals the equilibrium constant and the Gibbs energy change under the actual conditions is zero.

A
True
B
False

Choose one

1 point

Which relationship follows from $\Delta G^\circ=-RT\ln K$ ?

A
If $\Delta G^\circ<0$ , then $K<1$ .
B
If $\Delta G^\circ<0$ , then $K>1$ .
C
If $\Delta G^\circ=0$ , then $K>1$ .
D
The value of $K$ cannot be related to $\Delta G^\circ$ .

Choose one

1 point

Which statement correctly describes the thermodynamics of melting at constant temperature and pressure?

A
Melting is spontaneous at every temperature because both changes are positive.
B
Melting is nonspontaneous above the melting temperature because it is endothermic.
C
Melting is spontaneous above the melting temperature and has $\Delta G=0$ at the melting point.
D
Melting has $\Delta H<0$ and $\Delta S<0$ above the melting point.

True or false

1 point

True or false: A spontaneous process must occur rapidly.

A
True
B
False

Choose one

1 point

Which physical change generally produces an increase in entropy?

A
A gas is compressed into a smaller volume.
B
A liquid freezes into a solid.
C
A liquid vaporizes into a gas.
D
A gas condenses into a liquid.

Choose one

1 point

At constant temperature and pressure, what does $\Delta G<0$ indicate for a process written in the forward direction?

A
The forward process is nonspontaneous and the reverse process is favored.
B
The forward process is spontaneous.
C
The system is necessarily at equilibrium.
D
The process must have a negative enthalpy change and a positive entropy change.

Written response

1 point

What field of chemistry studies how quickly a reaction occurs, rather than whether it is thermodynamically favorable?

Choose one

1 point

Which combination of enthalpy and entropy changes predicts that a process is spontaneous at all temperatures, assuming the values remain approximately constant?

A
$\Delta H<0$ and $\Delta S>0$
B
$\Delta H>0$ and $\Delta S<0$
C
$\Delta H<0$ and $\Delta S<0$
D
$\Delta H>0$ and $\Delta S>0$

Choose one

1 point

In an introductory reaction-quotient calculation, why are pure solids and pure liquids omitted from $Q$ ?

A
All reactants and products must always appear in $Q$ .
B
Only gaseous reactants are included in $Q$ .
C
Pure solids and pure liquids are omitted from $Q$ .
D
Only products are included in $Q$ .

Written response

1 point

At $298\ \mathrm{K}$ , a reaction has $\Delta H^\circ=-92.0\ \mathrm{kJ\,mol^{-1}}$ and $\Delta S^\circ=-198\ \mathrm{J\,mol^{-1}\,K^{-1}}$ . Calculate $\Delta G^\circ$ in kJ mol⁻¹. Enter the answer to three significant figures; no nonzero tolerance is used.

Fill in the blank

1 point

For the balanced reaction $2\mathrm{A(g)}+\mathrm{B(g)}\rightarrow3\mathrm{C(g)}$ , complete the standard entropy-change expression: $\Delta S^\circ_{\mathrm{rxn}}=$ .