3.4-3.5

Question 1

Why do ionic compounds not exist as gases at STP?

Answer 1

Cations and anions are held together by very strong electrostatic forces that require a large amount of energy to overcome.

Question 2

mole fraction

Answer 2

Dimensionless quantity that expresses the ratio of the number of moles of one component to the number of moles of all components (xi = ni/nT)

Question 3

KMT (1)

Answer 3

A gas is composed of molecules separated from each other by distances greater than their own dimensions, and the molecules can be considered to possess mass but have negligible volume

Question 4

KMT (2)

Answer 4

Gas molecules are in constant random motion and frequently undergo perfectly elastic collisions with one another. Total energy of all molecules in the system remains constant.

Question 5

KMT (3)

Answer 5

Gas molecules exert neither attractive nor repulsive forces on one another

Question 6

KMT (4)

Answer 6

KEav = 1/2m(v_av^2) = CT where T is measured in kelvins

Question 7

RMS speed

Answer 7

Average molecular speed, v_rms = sqrt(3RT/molar mass)

Question 8

Diffusion

Answer 8

Gradual mixing of molecules of one gas with molecules of another by virtue of their kinetic properties

Question 9

Graham’s law of diffusion

Answer 9

Under the same conditions of temperature and pressure, rates of diffusion for gases are inversely proportional to the square roots of their molar masses. r1/r2 = sqrt(MM1/MM2)

Question 10

Effusion

Answer 10

The process by which a gas under pressure escapes from one comportment of a container to another by passing through a small opening

Question 11

Explain the correction term a(n/V)^2 for a non ideal gas

Answer 11

(1) Intermolecular interaction that results in non ideal behavior depends on how frequently any two molecules closely approach each other.
(2) Frequency of encounters increases with square of # molecules/unit volume since the probability of finding each of the two molecules in a region is proportional to n/V
(3) a is a proportionality constant

Question 12

Explain the correction of V - nb for a non ideal gas

Answer 12

Each molecule occupies a finite intrinsic volume, so the effective volume of the gas is V - nb. The term nb represents the volume occupied by n moles of the gas.

Question 13

What do a and B refer to?

Answer 13

a indicates how strongly molecules of a given type of gas attract one another
There is a rough correlation between molecular size and b

Question 14

van der Waals equation

Answer 14

(P + a(n/v)^2)(V - nb) = nRT