P-CHEM Final

Question 1

pressure is —– proportional to volume

Answer 1

inversely

Question 2

volume is ——– to temperature

Answer 2

proportional

Question 3

in PV=nRT what is the purpose of the R constant?

Answer 3

to ensure the units are the same on both side of the equation

Question 4

what is the R constant?

Answer 4

8.314 j/mol*k

Question 5

in the Dieterici equation of state what are the units of b?

Answer 5

m^3/mol

Question 6

in the Dieterici equation of state what are the units of a?

Answer 6

J∙m^3/mol^22

Question 7

why is PV=NRT not a perfect equation?

Answer 7

It doesn’t describe all gas behavior. Thus, it is an approximation of most gas behavior.

Question 8

What 2 implications make a gas a perfect gas?

Answer 8

The gas molecules do interact with one another. The gas atoms do not collide and the molecules themselves do not have volume

Question 9

is the van der Waals “a”
parameter positive or negative for all gases?

Answer 9

always positive

Question 10

What is the role of the van der Waals “a”
parameter

Answer 10

to lower the pressure of a real gas to values lower than that of a perfect gas

Question 11

van der Waals “a”
parameter lowers the pressure of the real gas to larger extent if the —- is smaller
hint
p real- p perfect = -(n^2*a)/ V^2

Answer 11

volume

Question 12

The van der Waals a parameter is associated with the gas molecules interactions with each other. How does this influence the pressure of a real gas?

Answer 12

Interactions between gas molecules lowers the pressure. Thus, a smaller volume means more interactions and the real pressure is significantly lower than predicted by PV=nRT

Question 13

What does the b parameter in the van der Waals equation account for ?

Answer 13

The volume of the gas molecules themselves

Question 15

What does the compressibility factor describe about a gas ?

Answer 15

How closely the gas of interest behaves like a perfect gas

Question 16

What variable of the PV=nRT equation does the compressibility factor analyze?

Answer 16

The pressure

Question 17

if Z < 1 than the pressure of the real gas is —– than that of a perfect gas

Answer 17

less than aka the observed pressure is too low

Question 18

if Z > 1 than the pressure of the real gas is —– than that of a perfect gas

Answer 18

greater than aka the pressure of the real gas is too high

Question 19

How does the b(volume) parameter of the Van der Waals equation affect the numerical magnitude of the Z(compression factor)

Answer 19

The b parameter increases Z because the B parameter is always positive

Question 20

How does the a(attractive forces) parameter of the Van der Waals equation affect the numerical magnitude of the Z(compression factor)

Answer 20

The a parameter decreases the value of the compression factor

Question 21

Are Van der Waals parameters dependent on temp?

Answer 21

No

Question 22

What is residual volume?
involves low pressure or high volume conditions

Answer 22

per mold volume of real gas - per molar volume of perf gas

Question 23

What is the residual volume of a perfect gas

Answer 23

0

Question 24

work done (dw=+) on a cylinder system requires a —- in volume

Answer 24

decrease (aka compression) via increase in applied exterior pressure

Question 25

work done by a cylinder system requires a --- in volume

Answer 25

increase ( aka expansion ) via decrease in applied exterior pressure

Question 26

compression and expansion of a piston stop when the ---- pressure is equal to the ----- pressure are equal

Answer 26

interior and exterior

Question 27

Work is inexact bc it is ------ dependent

Answer 27

path

Question 28

during an isothermal compression, heat flows --- the system to maintain temp constant

Answer 28

out of

Question 29

during an isothermal expansion heat flows --- the system to maintain temp constant

Answer 29

into

Question 30

heat and work are ---- because they are path dependent

Answer 30

inexact

Question 31

what can Euler's test be used to determine?

Answer 31

if a differential is exact or inexact

Question 32

Internal energy is the energy of

Answer 32

a single molecule

Question 33

Internal energy is a state function, and its differential ∂U is ----

Answer 33

exact aka path independent

Question 34

Every atom in every molecule has at minimum ---- degrees of freedom

Answer 34

3

Question 35

A linear molecule has the capability to do --- additional rotations

Answer 35

2

Question 36

a non linear molecule is capable of ---- rotations

Answer 36

3

Question 37

------- do not practically count towards a molecule’s internal energy hint rotations, vibrations, translations

Answer 37

vibrations

Question 38

under isothermal conditions what is the change in internal energy(du=?)

Answer 38

0J because the temp is constant

Question 39

what is the change in heat under isothermal condtions?

Answer 39

dq=-dw

Question 40

is CP,m greater than or lesser than CV,m

Answer 40

greater than

Question 41

what is the change in heat of adiabatic system?

Answer 41

dq=0J because heat transactions with the exterior environment are not possible to maintain the temp constant

Question 42

Does an adiabatic system experience a change in internal energy