Physical Chemistry Review. – Flashcards

Temperature is a very important classical property of a material. Which statement below is NOT true regarding temperature? A) A very common description of temperature is related to the average speed of molecules in a sample. B) There is only one definite way in which to measure temperature: a mercury thermometer. C) There are many different temperature scales, each with a different reference point or gradation. D) A change in temperature can result in changes to a multitude of physical properties in the material.

Consider a process in which the system does 100 J of work while receiving 150 J of heat from the surroundings. To be consistent with the textbook, how should we report these values?

The ideal gas law actually combines a number of more specific observations regarding the behavior of gases. Which idea below is NOT supported by the ideal gas law? A) Boyle's Law: for a fixed amount of gas at constant temperature, the volume is inversely proportional to its pressure. B) Van der Waals Rule: since gas particles of different gases have different sizes, the volume available to a gas depends on its identity. C) Charles' Law: for a fixed amount of gas at constant pressure, the volume of a gas is directly proportional to its temperature. D) Avogadro's Principle: at constant pressure and volume, all gases have the same molar volume (V/n).

Statistical mechanics is a powerful tool to connect bulk properties to microscopic characteristic. Which statement below is NOT a fundamental postulate of statistical mechanics? A) Macroscopic observables are calculated by extrapolating quantum energies to the classical limit. B)When we observe macroscopic properties, they are ensemble averages. C) All macroscopic observables are continuous variables. D) Identical particles will behave the same way under the same conditions.

Boltzmann's definition of the entropy was a breakthrough in understanding statistical thermodynamics. What is the best definition of Boltzmann's entropy? A) The Boltzmann entropy is a count of the accessible energy levels at a given temperature. B) The Boltzmann entropy is a measure of the randomness of an ensemble. C) The Boltzmann entropy is a count of the total distinct microstates in a system. D) The Boltzmann entropy is a measure of the useful work available in an ensemble.

Consider the two populations for rotational energy levels in a gas sample shown below. What changes in the system could cause the shift from average population A to average population B? A) The volume can be increased at constant pressure. B) The pressure can be decreased by 2× while the volume is increased by 2×. C) The pressure can be increased at constant volume. D) The pressure can be decreased at constant volume.

Why do we spend so much time focusing on microscopic degrees of freedom when studying bulk thermodynamics? A) We can only calculate bulk thermodynamic quantities as ensemble averages over the microscopic states. B) Intermolecular forces determine the state of the material and are therefore crucial to calculating bulk thermodynamics. C) Quantum effects play an important role in determining the bulk thermodynamics of a system. D) The bulk thermodynamics is heavily dependent upon how energy is distributed among the microscopic degrees of freedom.

Which statement below is NOT true regarding the Equipartition Function? A) Vibrational degrees of freedom will contribute twice for each accessible vibrational state. B) At room temperature, we do not need to carefully select the rotations which contribute to N ep. C) At room temperature, we should not include all vibrational degrees of freedom when calculating N ep. D) Thermal energy is divided among 6 translational degrees of freedom, 3 position and 3 momentum degrees of freedom.

We were able to reduce the vibrational partition function from an infinite series to a function of a single exponential, but only approximately. Which approximation below was NOT used? A) We assumed that the separations are relatively small, due to high temperature or lower vibrational constant. B) We assumed that the vibrational motion is purely harmonic. C) We assumed that the vibrational energy can be expressed as vωe D) We assumed that the energy levels were close enough to allow integration instead of summation.

The connection between the Equipartition Principle and the translational partition functions helped to demonstrate that the temperature of a system depends on the easily excited degrees of freedom. Why should this be true? A) In systems with easily excited degrees of freedom, small increases in the pressure make excited states more accessible, increasing the temperature. B) In systems with easily excited degrees of freedom, the potential energy is no longer dependent on the temperature of the system. C) In systems with easily excited degrees of freedom, a change in the entropy requires energy changes on the order of thermal energy. D) In systems with easily excited degrees of freedom, thermal energy is sufficient to allow one to treat the energy levels as a continuum.

The connection between the Maxwell-Boltzmann distribution and the translational partition function allowed us to better understand the distribution of speeds. Which statement below is NOT a consequence of the translational partition function? A) The pressure of the gas increases as the velocity increases. B) An increase in the temperature will result in the shifting the distribution to higher energies. C) The population of the lowest speeds is very small. D) The population of the highest speeds is very small.

Even though the derivation of the pressure of a non-ideal gas is quite complicated, it is built on some reasonable assumptions. Which statement below is NOT one of these assumptions? A) We only consider the interaction between pairs of molecules. B) We assume that all of the molecules are indistinguishable. C) The interaction potential for a given pair of molecules is fluctuates throughout the entire volume of the sample. D) The range of interactions is much smaller than the dimensions of the volume.

What are the physical origins of the van der Waals parameters for describing a non-ideal gas? A) The value a corresponds to the change in entropy with respect to volume, while b corresponds to the change in energy with respect to entropy. B) The value b corresponds to the change in entropy with respect to volume, while a corresponds to the change in energy with respect to entropy. C) The value a corresponds to a reduction in the effective volume of the gas; b corresponds to a decrease in the effective pressure due to intermolecular forces. D) The value b corresponds to a reduction in the effective volume of the gas; a corresponds to a decrease in effective pressure due to intermolecular attractions.

Why does the second virial coefficient become more negative as one moves down the noble gas group? A) As the electron distributions become larger, the electrostatic repulsion terms get smaller, reducing the repulsion. B) As the mass of the atoms increase, the speeds decrease, requiring a lower pressure. C) The increased volume of the larger noble gases reduces the effective volume of the gas. D) The larger noble gases are more easily polarized, causing stronger induced dipole interactions.

Of the intermolecular potential energy terms listed below, which one does NOT demonstrate an R −6 dependence? A) Electrostatic interaction between nuclei B) Dipole-induced dipole interactions C) Dipole-Dipole interactions D)Dispersion forces

What do the peaks in the pair correlation function tell us about? A) Maxima correspond to higher densities than random; minima correspond to lower densities than random. B) Maxima correspond to regions of higher temperature; minima correspond to regions of lower temperature. C) The more bumpy the pair correlation function, the more random the distribution of molecules. D) The further out the first peak occurs, the stronger the intermolecular attractions.

In terms of the van der Waals coefficients, what are the predicted values of the second virial coefficient B2(T) in the limits of high temperature? A) a B)-a C) b D)-b E) a/RT F) -a/RT G) b/RT H) -b/RT

In terms of the van der Waals coefficients, what are the predicted values of the second virial coefficient B2(T) in the limits of low temperature? A) a B)-a C) b D)-b E) a/RT F) -a/RT G) b/RT H) -b/RT

Which item below is NOT a characteristic parameter of molecular collisions? A) The mean free path B) The energy of the center of mass of the particles C) Collision cross section D) The average collision frequency

Of the stated properties below, which is least likely to cause an increase in the collision cross section of a particle? A) Greater polarizability of the particle B) An increase in the number of neutrons in the nucleus C) Increasing the number of atoms. D) An increase in the mass of the particle

The random walk offers a simplistic description of random motion in a fluid. Which statement below is NOT accurate regarding the random walk? A) The most probable location after taking N steps is exactly where you started. B) It is impossible in the random walk for the particle to move in an uninterrupted straight line. C) The random walk offers us a good model for diffusion through a fluid. D) The longer a random walk is allowed to progress, the more likely you will end up far from the starting point.

Diffusion is transport along a density gradient as defined in Fick's First Law. Which physical property is proportional to this density gradient? A) The flux B) The diffusion coefficiant C) The mean free path D) The collision frequency

Which of the following changes would result in a decrease in the diffusion constant for a compound? A) Decreasing the number density B) Decreasing the collision cross section C) Decreasing the collision frequency D) Increasing the mean-free path

Diffusion across or through a solid is another application of Fick's Laws. Which of the following cases is NOT considered a diffusion process involving solids? A) Removal of waste from blood using a dialysis membrane B) Oxygen passing through a contact lens to reach the eye C)Movement of hydrogen gas through the crystal structure of steel, resulting in embrittlement D) Movement of a water drop as it spreads out on a table

The collision cross section for ethane is 84 Å^2 and for He is 22 Å^2 . Which is less viscous at 400 K, ethane gas or He gas? A) He B) ethane C) The gases are of the same viscosity.

Our thermodynamic potentials are expressed in terms of conjugate pairs of variables. Which pair below is NOT a conjugate pair when describing the internal energy of a system? A) Chemical potential and number of moles B) Pressure and Volume C) Entropy and Pressure D) Temperature and entropy

The introduction of the different thermodynamic potentials is a simplifying step for our mathematical analysis. Which statement below is most accurate? A) The enthalpy is most useful when we wish to control entropy and volume in our system. B) The Helmholtz energy is most useful when we wish to control pressure and entropy in our system. C) The internal energy is most useful when we wish to control pressure and temperature. D) The Gibbs energy is most useful when we wish to control temperature and pressure in our system.

Careful description of our systems and processes is crucial to building a correct thermodynamic description. Which statement below is NOT correct? A) During a quasistatic, isobaric process acting on a closed system, the pressure changes, but very slowly. B) It is possible to have a closed, isolated system, but not an open, isolated system. C) If an adiabatic system does work on the surroundings, then the internal energy of the system must decrease. D) For a quasistatic ideal gas system, being isothermal is equivalent to being isoenergetic.

Which of the following gases has the largest heat capacity at 298 K? A) O2 B) N2O C) NH3 D) HF

Select the correct expression of the enthalpy H for a monatomic ideal gas in terms of P and V. A) H= 1/2PV B) H=3/2PV C) H= 5/2 PV D) H= 7/2PV

Indicate whether each of the following parameters would be positive ("+"), negative ("-"), or zero ("0") during an irreversible, adiabatic compression of an ideal gas from volume V1 to a smaller volume V2. T2= dT = dP= w= q= dS= dE= dH=

For the isobaric heating of an ideal gas, indicate whether each of the following would be positive ("+"), negative ("-"), or zero ("0") dE= q= dP= dT= dV=