ChemII: Thermodynamics

Which of the following is an application of the second law of thermodynamics? Multiple choice question.

A gas expands because matter tends to spread out.

The reaction between hydrogen and oxygen to form water is represented by the balanced equation 2H2 (g) + O2 (g) → 2H2O (l); ΔHo = -572 kJ. What is the most likely reason that this reaction is vigorously spontaneous?

A large quantity of heat is released.

Which of the following statements correctly reflect the relationship between the spontaneity of a reaction and the sign of ΔH? Select all that apply.

It is possible for an exothermic process to be nonspontaneous. An endothermic process may be spontaneous under one set of conditions but nonspontaneous at a different temperature and pressure.

An endothermic process may be spontaneous if ______

the product particles have more freedom of motion than the reactant particles

Select the definition of entropy in terms of the number of microstates over which the energy of a system can be dispersed. Multiple choice question.

S = k ln W

Which of the following correctly describes the first law of thermodynamics?

Energy can be converted from one form to another, but it cannot be created or destroyed.

Which of the following options correctly describe entropy? Select all that apply. Multiple select question.

Entropy is a measure of the energy dispersal of a system. The greater the freedom of motion of particles in a system, the greater the entropy of the system.

Which of the following processes are spontaneous under standard conditions? Select all that apply. Multiple select question.

Heat flowing from a hotter object to a colder object Ice melting at room temperature A teaspoon of table salt dissolving in a glass of water

Select the endothermic processes that may be spontaneous due to changes in the freedom of motion of particles in its system. Select all that ap

KCl (s) −→−H2O→H2O K+ (aq) + Cl- (aq) H2O (s) → H2O (l)

Which of the following options correctly describe standard molar entropies? Select all that apply

Standard molar entropies are usually quoted at a temperature of 298 K. The units of standard entropy are J/mol⋅K. The standard entropy of a substance is its absolute entropy at 1 atm.

Which of the following is a correct description of the third law of thermodynamics?

The entropy of a perfect crystalline substance is 0 at 0 K.

The reaction between hydrogen and nitrogen to form ammonia is called the Haber process and is represented by the balanced equation 3H2 (g) + N2 (g) ⇌ 2NH3 (g); ΔHo = -91.8 kJ⋅mol-1. What is the most likely reason that this reaction is spontaneous in the forward direction? Multiple choice question.

A large quantity of heat is released.

In which of the following options does the first species of each pair have a greater standard entropy? Select all that apply. Multiple select question.

A more complex substance vs. a simpler substance in the same phase if their molar masses are similar A gas at 250°C vs. the same gas at 100°C

Which of the following processes are spontaneous under standard conditions? Select all that apply.

A soluble salt dissolves when it is mixed with water. Iron rusts when it exposed to salty water. A match continues to burns after it is lit.

Which of the following factors increase the likelihood that a reaction will be spontaneous? Select all that apply. Multiple select question.

Energy is released in the form of heat. A gas is generated from a liquid. A liquid is generated from a solid.

Match each symbol in the equation S = k ln W correctly with its meaning.

S- entropy k-boltzman constant W-number microstates ln-natural log

Which of the following conditions are specified by standard state conditions? Select all that apply.

Solutions are at a concentration of 1 M. Gases are at a pressure of 1 atm. The standard state of an element is its most stable allotropic form at standard state temperature and pressure.

Two unknown reactions (A and B) are analyzed. It is found that reaction A is exothermic, while reaction B is endothermic. Which of these reactions is spontaneous?

Spontaneity cannot be determined from the given information.

An atom of hydrogen is bound to a metal surface (but free to move across it) with 10 possible sites of attachment. What would be the effect of increasing the size of the metal surface to 20 possible sites?

The entropy would increase, but it would be less than double the original entropy.

In what way does the first law of thermodynamics relate to the spontaneity of a process?

The first law of thermodynamics cannot predict the direction of spontaneous change.

True or false: If a process is spontaneous in one direction, it is not spontaneous in the reverse direction under the same set of conditions.

True

The ______of a system, symbolized by the letter S, is related to the number of different possible ways the energy of a system can be dispersed.

entropy

The second law of thermodynamics states that the total _____ of the universe will _____ for any spontaneous process. Multiple choice question.

entropy; increase

The first law of thermodynamics states only that the total energy change of the universe is _____. However, the first law of thermodynamics _____ account for the direction of spontaneous change.

equal to zero; cannot

Entropy depends on the number of energetically _____ states that a system can be arranged in, called microstates. The greater the number of these states, the _____ the entropy of the system

equivalent; higher

A key factor that influences reaction spontaneity is changes in the ___________of motion of the particles in the system, i.e. the _______of the energy of motion of the particles.

freedom; dispersal

atch each state of matter with the appropriate characteristics at standard state.

gas -> pressure 1 atm liquid -> 1M concentration solid -> Pure substance in its most stable form

How is the number of microstates in a system, W, related to the entropy of the system, S?

ln W ∝ S

The different possible ways for arranging the particles of a system are called _____. The greater the number of these states, the _____ the entropy of the system. Multiple choice question.

microstates; larger

A process that can occur without a continuous input of energy is a(n) _____ process. Multiple choice question.

spontaneous

The ____ molar entropy of a substance has the symbol So and is defined as the entropy of 1 mole of the substance at a pressure of ____atm.

standard; one

The third law of thermodynamics states that a perfect _____of a pure solid substance has ___entropy at a temperature of 0 K.

zero; crystal