PChem

Which of the following properties is extensive?

a. density
b. temperature
c. pressure
d. particle number
e. none of the above

d. particle number

*Intensive properties are not dependent on the amount of matter present while extensive properties are dependent on the amount of matter present.

The internal energy U of an ideal gas is made up

a. only o fpotential energy due to interaction between the particles
b. both potential and kinetic energy
c. neither of potential nor of kinetic energy
d. only of kinetic energy of the gas molecule

d. only of kinetic energy of the gas molecule
Suppose we increase the temperature of a gas by a factor 2 (T2=2*T1). What is the relationship between the average speed of molecules?

a. v2=4*v1
b. v2=v1
c. v2=2*v1
d. v2=sqrt(2)*v1
e. v2=(1/2)*v1
f. none of the above

d. v2=sqrt(2)*v1

v_avg=(3*kb*T)/m

Suppose we increase the temperature of a gas by a factor 2 (T2=2*T1). What is the relationship between the kinetic energies?

a. E2=4*E1
b. E2=E1
c. E2=2*E1
d. E2=sqrt(2)*E1
e. E2=(1/2)*E1
f. none of the above

e. E2=(1/2)*E1

E=(3/2)*kb*T

If O2 and H2 behave as an ideal gas, and are at the same temperature, the average kinetic energy

a. of H2 is larger than that of O2
b. of H2 is smaller than that of O2
c. of the molecules in both gases is the same

c. of the molecules in both gases is the same
The Maxwell distribution law gives the probability distribution distribution of the speed of gas molecules. When temperature increases

a. the distribution curve becomes sharper
b. the area under the distribution becomes smaller
c. the average speed of the molecules decreases
d. the distribution curve becomes flatter
e. none of the above

d. the distribution curve becomes flatter
For an ideal gas, the molar heat capacity at constant pressure is

a. larger than the molar heat capacity at constant volume
b. smaller than the molar heat capacity at constant volume
c. equal to the molar heat capacity at constant volume
d. the negative of the molar heat capacity at constant volume
e. not related to the molar heat capacity at constant volume
f. none of the above

a. larger than the molar heat capacity at constant volume

R=Cp-Cv

Atmospheric pressure

a. decreases exponentially with altitude
b. increases exponentially with altitude
c. does not depend on temperature
d. none of the above

a. decreases exponentially with altitude

P=P0*exp((m*g)/(R*T))

In the van der Wall’s equation, the correction for volume accounts for

a. interactions between gas molecules
b. finite size of gas molecules
c. none of the above

b. finite size of gas molecules

*VDW EOS takes into account molecular size and molecular interaction forces

For an ideal gas, the compression coefficient is

a. z=1
b. z=0
c. z=-1
d. none of the above

a. z=1
The first law of thermodynamic states that

a. the energy of an isolated system increases as it approaches equilibrium
b. the energy of an isolated system decreases as it approaches equilibrium
c. The energy does not change with time in an isolated system
d. none of the above

c. The energy does not change with time in an isolated system

(dU/dt)=0

For a system at constant pressure, heat added to or subtracted from a system is equal to

a. the change deltaU in internal energy
b. the change deltaH in enthalpy
c. the change in deltaS in entropy
d. none of the above

b. the change deltaH in enthalpy
During reversible isothermal expansion of an ideal gas

a. deltaU=0 and deltaH>0
b. deltaU=0 and delta=0
c. deltaU=0 and deltaH<0
d. deltaU<0 and deltaH=0
e. deltaU>0 and deltaH=0
f. none of the above

b. deltaU=0 and delta=0
Which of the following is correct about the Joule-Thomson experiment?

a. deltaH=0
b. deltaU=0
c. W=0
d. none of the above

a. deltaH=0
For an ideal gas, the Joule-Thomson coefficient is

a. mu=(5/3)
b. mu=1
c. mu=0
d. mu=-1
e. mu=-(5/3)
f. none of the above

c. mu=0
If you draw P vs V for an ideal gas, the resulting curve

a. does not depend of the process
b. is steeper for an adiabatic process than for an isothermal process
c. is steeper for an isothermal process than for an adiabatic process
d. none of the above

b. is steeper for an adiabatic process than for an isothermal process
The second law of thermodynamics states that

a. the energy is conserved in an isolated system
b. The entropies of all perfectly crystalline substance is zero at T=0K
c. External work is need to pump heat from a system at low temperature to one at higher temperature

c. External work is need to pump heat from a system at low temperature to one at higher temperature
Which of the following statements is true for a Carnot cycle?

a. the efficiency of a Carnot cycle changes with time
b. A Carnot-like engine that includes irreversible processes is more efficient than one built only out of reversible processes
c. A Carnot engine can be used as a refrigerator
d. none of the above

c. A Carnot engine can be used as a refrigerator
The entropy change in a Carnot cycle is

a. positive
b. negative
c. zero
d. none of the above

c. zero
The efficiency of a Carnot engine depends only on

a. the type of gas
b. the ratio of temperatures Tc/Th, where Th is the higher temperature
c. none of the above

b. the ratio of temperatures Tc/Th, where Th is the higher temperature
For a reversible adiabatic expansion of a real gas, the entropy changes as

a. deltaS>0
b. deltaS=0
c. deltaS<0

b. deltaS=0
An isolated system is said to be in equilibrium if

a. deltaS>0
b. deltaS=0
c. deltaS<0

b. deltaS=0
Which of the following properties is intensive?

a. mass
b. volume
c. density
d. particle number
e. none of the above

c. density

*Intensive properties are not dependent on the amount of matter present while extensive properties are dependent on the amount of matter present.
*An extensive property divided by another creates an intensive property.

Suppose we decrease the temperature of a gas by a factor 2 (T2=T1/2). What is the relationship between the kinetic energies?

a. E2=4*E1
b. E2=E1
c. E2=2*E1
d. E2=E1/sqrt(2)
e. E2=(1/2)*E1
f. none of the above

e. E2=(1/2)*E1

E=(3/2)*kb*T

Let Pw be the pressure resulting from a 2m column of water and Ph be the pressure resulting from a 2m column of mercury. Which statement is true?a. Pw=Phb. PwPhf. none of the above
b. Pw
The first law of thermodynamics states that

a. the energy of an isolated system increases as it approaches equilibrium
b. the energy of an isolated system is conserved
c. the energy of an isolated system decreases as it approaches equilibrium
d. the entropy of all perfectly crystalline substances is zero at T=0K
e. external work is needed to pump heat from a system at low temperature to one at a higher temperature

b. the energy of an isolated system is conserved
Which of the following statements is true for a Carnot cycle?

a. the efficiency of a Carnot cycle depends on the ratio of temperatures Tc/Th, where Th is the higher temperature
b. Not all Carnot engines have the same efficiency
c. A Carnot engine that includes irreversible processes is more efficient than one built only out of reversible processes
d. a Carnot engine cannot be used as a refrigerator
e. none of the above

a. the efficiency of a Carnot cycle depends on the ratio of temperatures Tc/Th, where Th is the higher temperature

*All Carnot engines have the same efficiency
*A Carnot engine can be used as a refrigerator

Under constant temperature and volume conditions, a system is said to be equilibrium when

a. deltaG=0
b. deltaA=0
c. deltaS=0
d. deltaU=0
e. deltaH=0
f. none of the above

b. deltaA=0

*deltaG=0 at constant volume and pressure

How many phases has the following system: CaCO3(s) <-->CaO(s)+CO2(g)?

a. 1
b. 2
c. 3
d. none of the above

c. 3
How many different phases can at most co-exist in a two component system?

a. 1
b. 2
c. 3
d. 4
e. 5
f. none of the above

d. 4

*f=c-p+2, where f=0, c=2

Which statement is true for an ideal solution mixture of two components A and B?

a. it forms an azeotropic mixture
b. the liquid curve in the temperature-composition phase diagram is a straight line
c. the vapor curve in the temperature-composition phase diagram is a straight line
d. the vapor curve in the pressure-composition phase diagram is a straight line
e. Raoult’s Law applies
f. none of the above

e. Raoult’s Law applies
The following reaction describes dissociation of chlorine into atoms: Cl2<-->2*Cl. If the volume is decreased by half, the degree of dissociation

a. increases
b. decreases
c. depending on temperature may or may not change
d. will oscillate
e. none of the above

b. decreases

*kc=[Cl]^2/[Cl2]=(nCl^2/V^2)/(nCl2/V)=(nCl^2/nCl2)*(1/V)

An ideal solution of xa mole fraction of A and xb mole fraction of B, with vapor pressures Pa* for pure component A and Pb* for pure component B, has a vapor pressure P given by

a. P=Pa*-Pb*
b. P=Pa*+Pb*
c. P=(xa)(Pa*)-(xb)(Pb*)
d. P=(xa)(Pa*)+(xb)(Pb*)
e. P=(Pa*)(Pb*)

d. P=(xa)(Pa*)+(xb)(Pb*)
Assume two chemical reactions A+B<-->X+Y and X<-->Z, characterized by equilibrium constants k1 and k2, that are coupled leading to a resulting reaction A+B<-->Y+Z. The resulting equilibrium constant k3 is given by

a. k3=k1+k2
b. k3=k1-k2
c. k3=k1*k2
d. k3=k1^-1+k2^-1
e. k3=k1/k2
f. none of the above

c. k3=k1*k2

k=pi(ki)

For a chemical reaction A+B<-->C we measure an equilibrium constant k^0<1. Under standard conditions, the reaction will proceed spontaneously from a. left to right (A+B–>C)
b. right to left (C–>A+B)
b. right to left (C–>A+B)

*Look at the direction of the operator (k^0<1)

Assume that the enthalpy difference deltaH^0 between products and reactants in a chemical reaction is independent of temperature, and deltaH^0<0. How does an equilibrium constant kp^0 (describing the same reaction change if the temperature is increased? a. kp^0 increases
b. kp^0 decreases
c. kp^0 does not change
b. kp^0 decreases

*d(ln(kp^0))=-deltaH^0/R*(dT/T^2)
*Temperature and kp^0 are inversely related

In which type of reaction is the half-life independent on the concentration?

a. 0th order
b. 1st order
c. 2nd order
d. none of the above

b. 1st order
Assume a reaction A<-->B, characterized by rate constants kab and kba. These two rate constants are related to the equilibrium constant kc by

a. kc=kab+kba
b. kc=kab-kba
c. kc=kab*kba
d. kc=kab/kba
e. kc=kba/kab
f. none of the above

d. kc=kab/kba

*keq=kforward/kbackward

Assume a reaction A+B<-->Z. Empirically, wefind the fllowing relation between the rate of formation of a product Z and the concentrations of two reactants A and B: vz=kz[A]^0.5[B]^1.5. What would be the order of the reaction?

a. 0.5
b. 1
c. 1.5
d. 2
e. 2.5
f. none of the above

d. 2

*Add the exponents to determine overall order

Assume two 1st order reactions characterized by rate constants k1 and k2, with k2=4*k1. The half-life of reaction 1 is

a. double that of reaction 2
b. four times that of reaction 2
c. half that of reaction 2
d. a quarter of that of reaction 2
e. none of the above

b. four times that of reaction 2
If a reaction has a rate constant of k=6.3e-5 L/(mol*s), the reaction is

a. 0th order
b. 1st order
c. 2nd order
d. cannot be determined based on the given information
e. none of the above

c. 2nd order
How does the concentration [A] of a reactant A change with time in a 1st order reaction?

a. decreases linearly
b. decreases logarithmically
c. decreases exponentially
d. increases exponentially
e. increases logarithmically
f. increases linearly
g. none of the above

c. decreases exponentially
In the consecutive reaction A–k1–>X–k2–>Z, where X is an intermediate, the steady state condition applies when

a. k1 is much smaller than k2
b. k2 is much smaller than k1
c. none of the above

a. k1 is much smaller than k2
In the consecutive reaction A–k1–>X–k2–>Z, where X is an intermediate, which quantity is zero at steady state?

a. [X]
b. [Z]
c. [A]
d. d[Z]/dt
e. d[A]/dt
f. d[X]/dt
g. none of the above

f. d[X]/dt
In an enzyme-catalyzed reaction, if the concentration of substrate is very large, the reaction is

a. 3rd order in substrate
b. 2nd order in substrate
c. 1st order in substrate
d. 0th order in substrate
e. none of the above

d. 0th order in substrate
For an equilibrium system at constant pressure and temperature, the Gibbs energy is

a. deltaG=0
b. deltaG<0
c. deltaG>0

a. deltaG=0
Le Chatelier’s principle implies that

a. the equilibrium cannot be shifted by changing pressure or concentration
b. volume or pressure changes can shift the equilibrium
c. And equilibrium constant can change to counteract any disturbance to a system at equilibrium

b. volume or pressure changes can shift the equilibrium
When equilibrium is reached, the total Gibbs energy of the reactants and products

a. is the same
b. differs, but has the same sign
c. differs in both value and sign
d. is both zero
e. adds up to zero
f. none of the above

a. is the same
Assume two chemical reactions A+B<-->X+Y and X<-->Z, characterized by Gibbs energy differences (between products and reactants) deltaG1 and deltaG2. When coiuple the two reactions, one finds for the resulting reaction A+B<-->Y+Z

a. deltaG=(deltaG1)(deltaG2)
b. deltaG=(deltaG1)/(deltaG2)
c. deltaG=deltaG1+deltaG2
d. deltaG=deltaG1-deltaG2
e. none of the above

c. deltaG=deltaG1+deltaG2

deltaG=sum(deltaGi)

The following reaction describes dissociation of chlorine into atoms: Cl2<-->2*Cl. If the volume is increased, the degree of dissociation

a. decreases
b. increases
c. does not change

b. increases

*kc=[Cl]^2/[Cl2]=(nCl^2/V^2)/(nCl2/V)=(nCl^2/nCl2)*(1/V)
*kc and volume are directly related

For a chemical reaction A+B<-->C we measure an equilibrium constant k^0>1. Under standard conditions, the reaction will proceed spontaneously from

a. left to right (A+B–>C)
b. right to left (C–>A+B)

a. left to right (A+B–>C)
Assume a chemical reaction A+B<-->C in equilibrium. When we remove a certain about of B, the equilibrium

a. shifts to the left
b. shifts to the right
c. stays unchanged

a. shifts to the left
Another way to shift the equilibrium is to couple the reaction of interest with a second one. To make an unfavorable reaction possible, what is the requirement for the second reaction?a. deltaG2^0deltaG1^0c. deltaG2^0+deltaG1^0>0d. deltaG2^0+deltaG1^0<0e. none of the above
d. deltaG2^0+deltaG1^0<0 *deltaGtot must be negative to be spontaneous or favorable
In a van’t Hoff plot, ln(Kp^0) is plotted as a function of the inverse temperature 1/T. If deltaH^0 is independent of temperature one obtains a straight line. From slope and intercept one finds

a. slope: -deltaS^0/R
b. intercept: -deltaS^0/R
c. intercept: -deltaH^0/R
d. intercept: -deltaH^0/R-deltaS^0/R
e. slope: -deltaH^0/R-deltaS^0/R
f. none of the above

f. none of the above

ln(kp^0)=-deltaH^0/R+deltaS^0/R

Which of the following is true for an equilibrium constant kc^0?

a. its value does not depend on temperature
b. its value does not depend on the units of concentration
c. its value depends on the stoichiometric equation used in its definition

c. its value depends on the stoichiometric equation used in its definition
Assume that the enthalpy difference deltaH^0 between products and reactants in a chemical reaction is independent of temperature, and deltaH^0<0. How does an equilibrium constant kp^0 (describing the same reaction) change if the temperature is decreased? a. kp^0 decreases
b. kp^0 increases
c. kp^0 does not change
b. kp^0 increases

*ln(kp^0) is proportional to (-deltaH^0/R)*(1/T)

How many different phases can at most co-exist in a three component system?

a. 1
b. 2
c. 3
d. 4
e. 5
f. none of the above

e. 5

*f=c-p+2, where f=0 and c=3

Determine the number of degrees of freedom for ice in a solution of water and alcohol.

a. 0
b. 1
c. 2
d. 3
e. none of the above

c. 2

*f=c-p+2, where c=2 (water, alcohol) and p=2 (liquid, solid)

Consider an ideal solution mixture of components A and B in equilibrium with vapor. A is more volatile than B. Compared to the liquid, the vapor contains

a. less of A
b. less of B
c. equal amounts of A and B
d. none of the above

b. less of B

*More volatile will vaporize first, therefore there will be more A in the vapor state than in the liquid state relative to B

At triple point, what is the thermodynamic quantity that is the same for all three phases?

a. internal energy U
b. entropy S
c. chemical potential mu
d. enthalpy H
e. none of the above

c. chemical potential mu
Which of the following quantities has a discontinuity in a 1st order phase transition?

a. Gibbs energy G
b. entropy S
c. enthalpy H
d. none of the above

b. entropy S
Consider water above the critical temperature Tc. Which of the following statements is correct for this system?

a. only one phase exists
b. the number of possible phase depends on the pressure in the system
c. there will be a liquid vapor transition
d. none of the above

a. only one phase exists
How many independent components are present in the following system: CO(g)+3*H2(g)<-->CH4(g)+H2O(g)?

a. 1
b. 2
c. 3
d. 4
e. none of the above

c. 3

4-1=3

Which of the following is correct for a completely immiscible two component solution?

a. Raoult’s law applies
b. its bioling point is that of the more volatile component
c. it has a higher boiling point than the individual components
d. it has a lower boiling point than the individual components
e. none of the above

d. it has a lower boiling point than the individual components

*Each component supplies much more pressure so it boils faster (lower temperature)
*a. for ideal and miscible
*c. there’s more pressure so Tbp will be lower

Consider an ideal solution mixture of components A and B in equilibrium with vapor. B is more volatile than A. Compared to the liquid, the vapor contains

a. less of A
b. less of B
c. equal amounts of A and B
d. none of the above

a. less of A
Which of the following is true during steam distillation?

a. the composition of the vapor phase depends on that of the liquid phase
b. the composition of the vapor phase does not change
c. the composition of the vapor and liquid phases is always identical
d. none of the above

b. the composition of the vapor phase does not change

*a. true for miscible cases
*c. true at azeotropic point

Which is true for an azeotropic mixture of two liquids?

a. the composition of vapor and liquid phases are not identical
b. it corresponds to an ideal solution made out of 50% of each liquid
c. it cannot be further purified by distillation
d. none of the above

c. it cannot be further purified by distillation
Which of the following has a discontinuity in a 1st order phase transition?

a. Gibbs energy G
b. volume V
c. enthalpy H
d. none of the above

b. volume V
Assume a chemical reaction A+B<-->C. When we add a certain amount of B, the equilibrium

a. shifts to the left
b. shifts to the right
c. stays unchanged

b. shifts to the right
For the chemical reaction, 2H–>H2 at constant volume, the entropy change is

a. deltaS<0
b. deltaS>0
c. deltaS=0

a. deltaS<0
Is the change in Helmholtz energy for the above reaction at room temperature

a. deltaA=0
b. deltaA<0
c. deltaA>0

c. deltaA>0
x

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