question

What kind of interactions occur when the Henry's law constant is greater than the pure vapor pressure?

answer

Unfavorable (repulsive) interactions

question

The Raoult's law standard state is a physically realizable state

answer

True

question

The Henry's law standard state is a physically realizable state

answer

False

question

Fugacity is to pressure as activity is to (blank).

answer

Concentration

question

What do we call the system when a reacting system has fully equilibrated?

answer

Equilibrium

question

What is the heat of mixing for an ideal mixture?

answer

Zero

question

If DeltaVmix is negative, what does that tell you about the interactions between the components of the mixture?

answer

They are generally favorable (attractive)

question

Write the mathematical expression for chemical potential for a component in an ideal mixture

answer

mu=mu* + RT ln(x)

question

If a mixture follows Raoult's Law, describe the interactions between the different molecules

answer

They are the same as between themselves (behaving as though pure)

question

What happens to the boiling point of a mixture compared to the pure solvent (nonvolatile solute)?

answer

Rises

question

Write the definition of chemical potential

answer

mu=(dG/dn)T,p,n

question

At a given temperature and pressure, which phase is thermodynamically preferred?

answer

The one with the lowest chemical potential

question

Write the fundamental equation of chemical thermodynamics

answer

dG=-SdT+VdP+sum(mudni)

question

As pressure is increased, what happens to the boiling point of a liquid?

answer

It increases

question

What property drives mixing for an ideal mixture?

answer

Entropy

question

Does the Gibbs energy increase or decrease with an increase in pressure?

answer

Increases, because (dG/dP)T=V and V is positive

question

If a reaction is exothermic, what happens to DeltarG if the temperature increases? Think Le Chatelier

answer

DeltarG will increase

question

Why do we need fugacity

answer

To account for the behavior of real gases (attractions, repulsions)

question

Under what conditions are two phases in equilibrium?

answer

When they have the same chemical potential (or molar Gibbs energy)

question

What is the maximum number of phases that can coexist at a particular temperature and pressure?

answer

3

question

Write the fundamental equation of thermodynamics

answer

dU=TdS-pdV

question

Write the Gibbs equation (derived from the fundamental equation) for the Gibbs energy

answer

dG=-SdT+VdP

question

What are the natural variables of the Gibbs energy?

answer

temperature and pressure

question

Why is the Gibbs energy a useful quantity?

answer

It tells us the maximum non-expansion work a process can produce; how much of the energy is 'useful'

question

Does the Gibbs energy increase or decreases as the temperature increases?

answer

Decreases, because dG/dT,p=-S

question

How o you maximize the efficiency of a Carnot engine?

answer

Create the largest temperature difference between the hot and cold parts of the engine

question

What is DeltaSuniverse fora phase transition at its normal transition temperature?

answer

0

question

Briefly explain why all processes are treated as reversible for the surroundings

answer

Because the surroundings are infinitely massive compared to the system.

question

Is DeltaSuniverse for a spontaneous, irreversible adiabatic expansion positive, negative, or zero?

answer

positive, the process is spontaneous

question

Write the definition of Gibbs energy

answer

G=H-TS

question

What is the sign of DeltavapH for any material?

answer

Positive, it takes an input of energy to vaporize something

question

Write the thermodynamic definition of entropy

answer

dS=dqrev/T

question

What makes a process spontaneous?

answer

DeltaSuniverse increases

question

True or False: the entropy of the system can spontaneously decrease

answer

True

question

True or False: the entropy of all substances is zero at zero Kelvin

answer

False

question

What is DeltaU for any isothermal process involving ideal gas?

answer

Zero

question

What is DeltaU for any cyclic process?

answer

Zero

question

What do we mean when we say an expansion process is reversible?

answer

p=p,ex throughout the process, no net work for the process and its opposite

question

Which process produces more work? reversible isothermal expansion of ideal gas or reversible adiabatic expansion of ideal gas?

answer

Reversible isothermal expansion of ideal gas produces more work

question

When two objects are at different temperatures and then placed in thermal contact, in which direction does heat flow?

answer

from the hot to the cold

question

On what variables does the internal energy of an ideal gas depend?

answer

Only on Temperature

question

Write the total differential of internal energy as a function of temperature and volume, U(T,V)

answer

dU=(dU/dV),T*dV+(dU/dT),V*dT

question

Write the definition of the constant volume heat capacity

answer

C,v=(dU/dT)v

question

Write the definition of enthalpy

answer

H=U+pV

question

What is meant by an adiabatic process?

answer

One in which no heat flows between system and surroundings.

question

What cna a closed system exchange with the surroundings?

answer

Energy but not matter

question

The Zeroth Law of Thermodynamics helps us to define what kind of Equilibrium?

answer

Thermal Equilibrium

question

Generally speaking, what physical quantity is the First Law of Thermodynamics Concerned with?

answer

Energy, or internal energy

question

Provide a brief explanation of the difference between heat and work at the molecular level?

answer

Work involves organized motion of the molecules; heat involved random motion

question

Write the mathematical definition of expansion work

answer

dwexp=-pexdV

question

Write the general expression for the chemical potential as a function of conditions.

answer

mu=mu^not+RTln(a)

question

Write the general form of the reaction quotient, Q

answer

Q=product(a^nu)

question

Write the relation between the equilibrium constant and the standard reaction Gibbs energy, DeltaGreaction

answer

DeltaGreaction^not=-RTln(K)

question

What is the value of the reaction Gibbs energy when the reacting system is at equilibrium?

answer

DeltaGreaction=0

question

If a reaction is exothermic, in what direction will it shift with an increase in temperature?

answer

Toward the reactants.

question

True or False: The equilibrium composition of a gas phase reaction can change when the vessel is compressed at constant temperature.

answer

True

question

True or False: The equilibrium constant of a gas phase reaction can change when the vessel is compressed at constant temperature.

answer

False

question

True or False: The equilibrium constant of a reaction generally changes with temperature.

answer

True

question

Write the general expression for the reaction Gibbs energy as a function of conditions

answer

DeltaGrxn=DeltaGrxn.not+RTln(Q)

question

What is the key difference between standard conditions and standard biological conditions?

answer

Standard biological conditions are at pH 7, [H+]=1*10^-7 molar, 1 molar

question

True or False: A transition state is a stable molecular configuration that can be isolated and studied

answer

False

question

Is the mathematical shape of the transition state a maximum, minimum, or saddle point on the potential energy surface?

answer

Saddle Point

question

To spectroscopically probe a transition state, what time scale of pulses do we need?

answer

Femtosecond

question

What is the sign of DeltaS(doubledagger)?

answer

Negative

question

What is the sign of DeltaG(doubledagger)?

answer

Positive

question

List three state variables that we use to describe the physical properties of a gas?

answer

T,p,V and n

question

The Zeroth Law of Thermodynamics defines what type of equilibrium?

answer

Thermal Equilibrium

question

Name one of the scientists whose work led to the development of the ideal gas law?

answer

Boyle, Charles, Gay-Lussac, Avogadro

question

Under what conditions of temperature and pressure do the ideal gas law hold true?

answer

Low pressure and high temperature

question

Upon what was the development of the Ideal Gas Law based?

answer

Experimental observation and proposed principles

question

What happens to the width of a probability distribution as the number of trials increases?

answer

The width narrows

question

How do we calculate the average of a property described by a continuous probability density function?

answer

h_bar=integral(h*f(h)dh)=

question

Define what is meant by an ensemble?

answer

A collection of individual items such as molecules

question

Consider placing balls in boxes. We put 2 balls in the first box, 1 in the second, and 1 in the third. Assuming all the balls are identical, and the order doesn't matter, what is the statistical weight of this arrangement?

answer

W=4!/(2!1!1!)=12

question

What is the statistical weight if all four balls are in the first box (of three)?

answer

W=4!/(4!0!0!)=1

question

According to the principle of equal a priori probabilities, which of these two arrangements (all balls in one box or some in all three) is preferred?

answer

Neither is preferred

question

State one of the constraints of the Boltzmann distribution

answer

Fixed number of molecules in the system; fixed total energy in the system

question

State the two constraints that lead to the Boltzmann distribution

answer

Fixed number of molecules; fixed total energy in the system

question

Write the mathematical expression of the partition function

answer

q=sum(e^-E_i/kT)

question

Write the Boltzmann expression for entropy in terms of statistical weight

answer

S=kln(W)

question

What does it mean when two states are said to be 'degenerate'?

answer

They have the same energy

question

Consider a container of Ar gas. What happens to the average speed of the Ar atoms as the temperature increaseS?

answer

The average speed increases.

question

At a molecular level, what is the source of the pressure of a gas?

answer

Collisions between the gas molecules and the walls of the container

question

Consider two samples of gas, He and Ar, at the same temperature. In which sample are the atoms, on average, moving faster?

answer

He, the average speed increases as the mass decreases.

question

State one of the assumptions in the kinetic molecular theory of gases, as we treated it.

answer

Molecules are in ceaseless, random motion; gas molecules have no size; all collisions are elastic.

question

Describe what is meant by the term "mean free path"

answer

The average distance a molecule travels before experiencing a collision.

question

What term do we use to describe the transfer of matter through another medium (such as a gas)?

answer

Diffusion

question

If the pressure decreases, but the temperature stays the same, what happens to the collision density?

answer

The collision density decreases; there are fewer collisions.

question

If there is a sharp change of concentration with distance, in what direction will diffusion occur?

answer

In the direction of the region with lower concentration.

question

Name one other property besides diffusion that is correctly predicted by the kinetic molecular theory of gases:

answer

Viscosity, thermal conductivity

question

What must phsyically happen between two molecules in order for a reaction to take place?

answer

Collision

question

A reaction is found to have the rate law v=k[A]^2. What is the order of the reaction?

answer

Second order

question

True or False: The rate of a reaction can be either positive or negative.

answer

False, reaction rates are always positive.

question

At a molecular level, what does the activation energy represent?

answer

The minimum energy required for a collision to lead to reaction.

question

True or False: If I know the overall reaction, I can write down the rate law?

answer

False, rate laws MUST be determined experimentally.

question

What is meant by the term "half life"?

answer

The time it takes for the concentration of a reactant to drop by half the initial value.

question

IF a reaction follows first order kinetic, how should I plot the data to determine the rate constant?

answer

As ln[A] vs. t

question

If a reaction takes place through a bi-molecular mechanism, what order will the rate law be?

answer

Second order, of the form v=k[A][B]

question

If we have a branching reaction that is under kinetic control, which product is more likely to be formed?

answer

The one with the larger rate constant.

question

If we have a branching reaction that is under thermodynamic control, which product is more likely to be formed?

answer

The one with the larger equilibrium constant.

question

In the steady state approximation, what do we assume about the concentration of an intermediate?

answer

The concentration does not change with time: d[I]/dt=0

question

Briefly describe how a catalyst speeds up a reaction

answer

By lowering the activation energy, or providing an environment that allows the reactants to interact in a way that favors production of product.

question

What step(s) generally determine the rate of reaction, fast or slow?

answer

Slow

question

What kind of chemical species is commonly involved in chain reaction mechanisms?

answer

Free radicals

question

In the Langmuir model, how deep can a surface be covered?

answer

One monolayer

question

What is one of the two types of energy we have from Newtonian mechanics?

answer

Kinetic, potential

question

Name one type of molecular motion that contributes to the heat capacity.

answer

Translational, vibrational, rotational.

question

How much does each rotational degree of freedom contributes to the heat capacity?

answer

1/2R

question

How many degrees of freedom does NH3 have?

answer

3N=12

question

How many vibrational degrees of freedom does NH3 have?

answer

3N-6=6

question

What quantity do we use as our 'energy ruler' in determining whether an energy state is high or low

answer

The quantity k.bT (or RT in molar units)

question

Name or describe one phenomenon that led to the development of quantum mechanics?

answer

Blackbody radiation, heat capacity of solids, photoelectric effect, electron diffraction

question

What did Einstein's explanation of the photoelectric effect tell us about light?

answer

Light can act like a particle, or the energy is quantized.

question

What was de Broglie's hypothesis about the behavior of particles?

answer

Particles should behave like waves to some degree

question

Name an experiment that proved de Broglie correct?

answer

Electron diffraction, two-slit experiment

question

How do we mathematically describe the behavior of a particle in quantum mechanics?

answer

With a wavefunction

question

What does the Hamiltonian operator account for?

answer

Total energy, kinetic plus potential

question

What does the quantity psi*psi tell us about?

answer

The probability of finding the particle between x and x+dx

question

State one of the requirement of a wavefunction?

answer

Continuous, continuous first derivative, square integrable, single valued, finite

question

If we have a free particle (no forces acting on it) that is described by a single value of momentum, where is the particle located?

answer

It has no location, it is delocalized over all space

question

In the formalism of quantum mechanics, how do we represent a physically measurable quantity?

answer

With the corresponding quantum mechanical operator.

question

How do we determine the expectation value of a physically observable quantity?

answer

Evaluate =integral(psi*j_hat*psi d(tao)

question

If a wavefunction is not an eigenfunction of a given operator, how should I write it?

answer

As a linear combination of eigenfunctions of that operator.

question

If a wavefunction is a linear combination of two eigenfunctions of the Hamiltonian, what values of energy can we measure?

answer

We can only measure one of the two eigenvalues.

question

True or False: Before an individual measurement on the wavefunction (in this case, a linear combination of two eigenfunctions of the Hamiltonian), I can predict the energy I will measure.

answer

False: I can predict the probability of each measurement, but not individual measurements.

question

After measuring the energy of the wavefunction in question 2, what happens to the wavefunction?

answer

The wavefunction 'collapses' to the eigenfunction corresponding to the measured energy.

question

What does it mean to say that two operators do not commute?

answer

The result of the measurements will be different depending on the order in which the measurements are performed.

question

What is a postulate?

answer

Something we assume to be true and use for further reasoning.

question

For the particle in a box, what happens to the energy as the size of the box decreases?

answer

Energy increases.

question

For the n=1 state of the particle in a box, what is probability of finding the right particle right next to the wall of the box?

answer

Zero

question

True or False: A particle confined to a box can have zero energy

answer

False; if the energy is zero, there is no particle in the box.

question

If I want to cause a transition between two energy states, what must the frequency of the incident light be?

answer

v=DeltaE/h; the incident light has to match the difference in energy of the two states.

question

What are the two conditions that must be met for a spectroscopic transition to occur?

answer

The energy of the photon must match the energy difference between the states. The transition dipole moment must be non-zero; the transition must be allowed.

question

In the classical limit, what does the probability density function look like for the particle in a box?

answer

Uniform probability of finding the particle anywhere in the box.

question

Why don't we worry about quantum effects when talking about an ideal gas?

answer

The size of the container is so large that the energy levels can be treated as a continuum; or the molecules are so far apart that they don't have any quantum interactions.

question

State one practical application of tunneling

answer

Schottky or tunneling diode; proton transfer; nuclear fusion; electron microscopy

question

Which are more likely to tunnel through a barrier, electrons or protons?

answer

Electrons, because of their smaller mass.

question

True or false: After tunneling through a barrier, a particle has less kinetic energy

answer

False; the energy is unchanged. The amplitude of the wavefunction, or the probability of being on the other side of the barrier, is reduced.

question

If we isotopically substitute deuterium for hydrogen, and the rate of reaction decreases, what does that tell us about the rate limiting step?

answer

It likely involves proton transfer, or proton tunneling.

question

In a 3-D situation, what aspect of the system leads to degenerate states?

answer

Symmetry

question

In addition to energy, the rigid rotor illustrates that what physical quantity is also quantized?

answer

Angular momentum

question

In what region of the electromagnetic spectrum do rotational transitions take place?

answer

The microwave region

question

How can we break the degeneracy of rotational states?

answer

With an external field, magnetic or electric.

question

TRue or False: Compared to k.bT, rotational levels are close together?

answer

True

question

Name one type of spectroscopy that allows us to measure vibrational transitions.

answer

IR or Raman spectroscopy

question

How many vibrational normal modes does H2O have?

answer

3n-6=3

question

True or False: a molecule can have no vibrational energy?

answer

False, there is always zero point energy of 1/2 h*nu

question

In what region of the electromagnetic spectrum do vibrational transitions take place?

answer

Infrared

question

True or False: Compared to k.bT, vibrational levels are very close together?

answer

False

question

True or False: Electrons circle the nucleus just like planets orbit the sun.

answer

False

question

Name one atom for which we have solve the Schrodinger equation exactly.

answer

Hydrogen (it's the only one)

question

What do we call solutions to the Schrodinger equation for the hydrogen atom?

answer

Atomic orbitals

question

In what range of the electromagnetic spectrum do we observe transitions between the electronic states of an atom?

answer

Visible to UV

question

What do we take as our zero of potential energy for a hydrogen atom?

answer

Infinite separation of the proton and electron

question

When constructing molecular orbitals from atomic orbitals, h ow many molecular orbitals will we have?

answer

The same as the number of atomic orbitals.

question

We generally talk about two types of molecular orbitals. Name one.

answer

sigma and pi

question

Why doesn't He form a diatomic molecule?

answer

The energy would have higher than for two unbonded atoms.

question

True or False: All molecular orbitals are localized along particular bonds

answer

False: Most molecular orbitals are delocalized over the whole molecule.

question

How does the Born-Oppenheimer approximation treat motion of the nuclei?

answer

Nuclei move much more slowly than the electrons.

question

True or False: If a molecule has a bound ground electronic state, all excited states are also bound.

answer

False: Excited states can be unbound. The molecule will dissociate if it is excited to such a state.

question

Name one process by which an electronically excited molecule relaxes and emits a photon.

answer

Fluorescence, phosphorescence, chemiluminescence.

question

What has a longer lifetime, fluorescence or phosphorescence?

answer

Phosphorescence

question

Why are the lifetimes different for fluorescence and phosphorescence?

answer

Because phosphorescence involves a forbidden transition.

question

What term do we use to describe breaking chemical bonds with light?

answer

Photolysis or photodissociation

question

Will fluorescence occur at longer or shorter wavelengths than the excitation?

answer

Longer wavelengths, or lower energy

question

What quantum mechanical model do we use for translations of molecules when building the partition function?

answer

Particle in a box

question

identify one of the key components of a laser:

answer

Gain medium, pump source, resonator cavity

question

True or False: at room temperature, we can reasonable assume that rotational levels are close together

answer

True: the rotational temperature is many times less than T

question

At the molecular level, what conditions are required for ideal behavior?

answer

No interactions (except for collisions)

question

What do we call a collection of individual microsystems?

answer

An ensemble

question

Given our collection of microsystems, how do we determine bulk properties?

answer

By taking the ensemble average of that property: M_bar=sum(M_j*P_J)=(sum(M_j*e^(-E_j/kT)))/Q

question

What thermodynamic properties do we keep constant in the canonical ensemble?

answer

N,V, and T

question

What is the interaction potential for an ideal gas?

answer

E_p=0 (or V=o)

question

What do we call the temperature below which a gas can condense?

answer

The critical temperature

question

Write the definition of the reduced temperature.

answer

T_r=T/T_c

question

Name one equation of state for real gases

answer

van der Waals, virial (Berthelot, Dieterici, Redlich-Kwong)

question

What happens when a real gas is compressed at a temperature below the critical temperature?

answer

It condenses

question

What do the two parameters in the van der Waals equation account for?

answer

Finite volume of the gas molecules and attractive interactions

question

For a particular gas at ambient in the van der Waals equation account for?

answer

Attractive interactions

question

According to the principle of corresponding states, how do we best compare the behavior of different gases?

answer

By comparing the reduced variables

question

In terms of molecular order, what characterizes the structure of a liquid at short and long distances?

answer

Short-range order, long range disorder

question

What can a closed system exchange with its surroundings?

answer

Energy, but not matter

question

The zeroth law of thermodynamics helps us to define what kind of equilibrium?

answer

Thermal

question

Generally speaking, what physical quantity is the First Law of Thermodyamics concerned with?

answer

Energy, or internal energy

question

Provide a brief explanation of the difference between heat and work at the molecular level?

answer

Work involves organized motion of the molecules, heat involves unorganized motion.

question

Give the mathematical definition of expansion work?

answer

delW_exp=-p_ex*dV

question

On what variables does the internal energy of an ideal gas depend?

answer

Only T

question

Write the total differential of internal energy as a function of temperature and volume U(T,V)

answer

dU=(dU/dV)_T*dV+(dU/dT)_v*dT

question

Write the definition of constant volume heat capacity

answer

C_v=(dU/dT)_v

question

Write the definition of enthalpy

answer

H=U+pV

question

What is meant by an adiabatic process

answer

One in which no heat flows between system and surroundings.

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