PhyChem PT 1

Question 1

Which condition can the air inside the balloon be brought into a more ideal condition?

A. reducing the radius of the balloon
B. reducing the release of flames
C. adding extra weight it carries
D. none of the above

Answer 1

D. none of the above

Question 2

Which of the following postulates of the Kinetic Molecular Theory best qualitatively explains why gases are easily compressed?

A. Collisions are perfectly elastic
B. Gases are composed of rigid particles in constant motion
C. Particles are in constant motion and may collide with another and walls
D. The volume of the particles is negligible compared to the total volume occupied

Answer 2

D. The volume of the particles is negligible compared to the total volume occupied

Question 3

Which of the following has the largest numerical value of speed?

A. average speed of helium
B. most probable speed of argon
C. root-men-square speed of hydrogen
D. all have the same value of speed

Answer 3

C. root-men-square speed of hydrogen

Question 4

Which of the following does NOT have a linear graph for an ideal gas?

A. P-V (constant n,T)
B. V-T (constant n,P)
C. P-T (constant n,V)
D. all are linear graphs

Answer 4

A. P-V (constant n,T)

Question 5

Which of the following pairs is directly proportional for an ideal gas?

A. v and M
B. v and m^(1/2)
C. v and T^(1/2)
D. v and m

Answer 5

C. v and T^(1/2)

Question 6

What is the most probable identity of a gas in a liter of a 250-g container at 30 °C and exerts 0.76 atm? The mass of the container with the gas is 254 g.

A. neon
B. xenon
C. nitrogen
D. chlorine

Answer 6

B. xenon

M= mRT/PV

Question 7

At what temperature must argon be, such that it will have the same root-mean-square velocity as helium at room temperature?

A. 250 °C
B. 625 °C
C. 2702 °C
D. 2976 °C

Answer 7

C. 2702 °C

(T/M)_He=(T/M)_Ar

Question 8

What is the partial pressure (torr) of methane in a 100-g mixture of methane and argon (39.95 g/mol) if it is found that argon is 10% by mass and the total pressure is 250 torr?

A. 11
B. 25
C. 225
D. 239

Answer 8

D. 239

P_CH4=(n_CH4)/[(n_CH4)+(n_Ar)]

Question 9

Consider moist air at SATP and 85% RH

What is the mole fraction of water vapor if the saturated vapor pressure is 23.756 mmHg

A. 0.027
B. 0.021
C. 0.011
D. 0.017

Answer 9

A. 0.027

RH=[(y_H2O)(P_T)]/(P*_H2O)

Question 10

Consider moist air at SATP and 85% RH

What is the molar mass (g/mol) of moist air?

A. 28.26
B. 28.10
C. 28.56
D. 28.38

Answer 10

C. 28.56

M moist air=(y_dry)(M_dry)+(y_H2O)(M_H2O)

Question 11

At standard conditions, 45 L of oxygen gas weighs about 64 g, whereas 45 L of hydrogen weighs only about 4 g. Which gas diffuses faster? By how much?

A. hydrogen, 4r_O2
B. hydrogen, 2r_O2
C. oxygen, 8r_H2
D. oxygen, 3r_H2

Answer 11

A. hydrogen, 4r_O2

[(r_H2)/(r_O2)]=√[(M_O2)/(M_H2)]

Question 12

At what altitude will the pressure of air (28.8 g/mol) be three-fourths of its pressure at sea level? Assume that temperature does not change at 28 °C.

A. 2.55 km
B. 2.89 km
C. 3.23 km
D 3.77 km

Answer 12

A. 2.55 km

P=(P_0)e^-[(Mg^2)/(RT)]

Question 13

There are three identical flasks containing H2, O2, and Ne at SATP. Which of these is TRUE?

A. Ne exerts the greatest pressure
B. H2 occupies the least volume
C. O2 contains the most number of particles
D. None of the above

Answer 13

D. None of the above

Question 14

Which of the following gases is the closest to ideality at a certain condition?

A. hydrogen
B. oxygen
C. xenon
D. formic acid

Answer 14

A. hydrogen

*most ideal gas is helium

Question 15

Which of the following is/are TRUE about the van der Waals EOS?

I. The volume correction is denoted as “b”
II. The pressure correction is denoted with “a”
III. The term “b” is four times the volume of a particle

A. I and II
B. I and III
C. II and III
D. I, II, and III

Answer 15

D. I, II, and III

Question 16

Calculate the following values at T=400K for argon that behaves as a Berthelot gas.

(dH/dP)_T=b-[3a/(RT^2)]
a=4.7x10-3 Pa.m^6.K/mol^2
b=2.5067x10-5 m^3/mol

Joule-Thomson coefficient (K/atm), Cp=20.79 J/Kmol

A. -0.122
B. -0.278
C. -0.334
D. -0.412

Answer 16

A. -0.122

µ_JT=[-(b-[3a/(RT^2)])/Cp]

Question 17

argon that behaves as a Berthelot gas.

(dH/dP)_T=b-[3a/(RT^2)]
a=4.7x10-3 Pa.m^6.K/mol^2
b=2.5067x10-5 m^3/mol

Inversion temperature (K)

A. 280.5
B. 8.225
C. 7.311
D. 281.4

Answer 17

B. 8.225

b-[3a/(RT^2)]=0

Question 18

Which of the following describes the Joule-Thomson experiment?

A. Isentropic expansion
B. Throttled adiabatic expansion
C. Adiabatic compression
D. Isothermal expansion

Answer 18

B. Throttled adiabatic expansion

Question 19

Which condition does NOT indicate a predomination of repulsive forces?

A. The value of Z is 1.0053
B. The value of φ is 1.0075
C. The value of µ_JT is 0.24 K/atm
D. None of the above

Answer 19

C. The value of µ_JT is 0.24 K/atm

Question 20

ΔP (cmHg)
-34.62 -29.75 -24.67 -19.30 -14.82 -8.36 -4.38 0
ΔT (K)
-1.53 -1.41 -1.26 -1.02 -0.80 -0.49 -0.2 0

What is the value of the Joule-Thomson coefficient (deg/atm) and the correct interpretation given the data above?

A. 0.048, gas cools upon expansion
B. 0.048, gas warms upon expansion
C. 3.5, gas cools upon expansion
D. 3.5, gas warms upon expansion

Answer 20

C. 3.5, gas cools upon expansion

ΔT=µ_JT(ΔP)+0