Horrocks L4

Question 1

How is the chemistry different in solution compared to the gas phase?

Answer 1

It is much more crowded in liquids, the percentage volume occupied is much higher in liquids

Question 2

Compare and contrast liquids and gases from the point of view of kinetics

Answer 2

liquids
- high density
- short mean free path
- solvation important
- most collisions are with solvent
- transport influenced by solvent

Gas
- low density
- long mean free path
- isolated molecules
- reactive collisions determine rates
- determined by average speeds

Question 3

List different forms of transport

Answer 3

• migration (electric charge)
• diffusion (matter or heat)
• viscosity (momentum)
• convection (matter)

Question 4

Define conductance

Answer 4

Conductance is a measure of how easily electric current flows through a material.

Question 5

Describe the conductance of gases

Answer 5

under ambient conditions gases are usually insulating because the molecules are neutral

Question 6

What is plasma

Answer 6

Plasma is a state of matter consisting of ionized gas with free-moving charged particles, including positive ions and electrons, that can conduct electricity and respond to electromagnetic fields.

Question 7

Describe the conductance of plasma

Answer 7

very high temperatures gases may ionize and become conductive. May also ionize in very high electric fields

Question 8

Describe the conductance of liquids

Answer 8

dissolves species may ionised under ambient conditions. Charge carriers are the ions

Question 9

What is Coulomb’s law

Answer 9

Coulomb’s Law describes the electrostatic force between two charged objects

Question 10

How do you calculate Coulomb’s law

Answer 10

F = q1q2/4πϵ0ϵrr2

Question 11

What is conductance denoted by

Answer 11

G

Question 12

How do we calculate conductance

Answer 12

G = 1/R = ∂I/∂V
Where R is resistance
I is current and V is voltage

Question 13

What is the units of conductance

Answer 13

units Siemens S = Ω−1

Question 14

What does conductance depend on

Answer 14

conductance depends on the cross-section area A and the length as well as the composition of the solution

Question 15

How do u calculate conductivity k

Answer 15

k = GKcell

Question 16

Define conductivity

Answer 16

Conductivity is a property of the material or solution that indicates its ability to conduct electricity. The higher the conductivity, the more easily current can flow.

Question 17

Write the equation that links conductance, area, length and conductivity

Answer 17

G = κ x A/L
κ - conductivity
A - cross section area
L - length

Question 18

What are the units of conductivity

Answer 18

Sm-1

Question 19

What does conductivity depend on

Answer 19

conductivity depends only on the solution composition T

Question 20

What is Λm

Answer 20

molar conductivity

Question 21

How do we calculate molar conductivity

Answer 21

Λm = κ/c
κ Is conductivity
c is concentration
Or
Λm = Λm0 - Kc^1/2
Λm0 is the limiting molar conductivity
K constant
c - concentration of electrolyte

Question 22

What is Λm0

Answer 22

the limiting molar conductivity

Question 23

What is the limiting molar conductivity dependent on

Answer 23

dependent only on the nature of the ions and solvent

Question 24

What is λ

Answer 24

ionic conductivities

Question 25

What is z

Answer 25

The charge number of an ion

Question 26

What is u

Answer 26

ionic mobility

Question 27

Define ionic mobility

Answer 27

Ionic mobility is defined as the velocity of an ion per unit electric field

Question 28

define viscosity

Answer 28

flux of linear momentum down a velocity gradient

Question 29

Define flux

Answer 29

Flux is the rate at which a quantity passes through a unit area

Question 30

What are the units of viscosity

Answer 30

Pa s

Question 31

Describe the characteristics of gas viscosity

Answer 31

independent of pressure and increases with temperature

Question 32

What can molecular motions in liquids be indirectly measured by

Answer 32

NMR, ESR, inelastic neutron scattering and viscosity

Question 33

What must a molecule acquire to move in a liquid

Answer 33

to move in a liquid a molecule must acquire sufficient energy to escape from its neighbours

Question 34

How do we calculate the viscosity in liquids

Answer 34

η = Aexp(Ea/RT) A pre exponentially constant

Question 35

Define diffusion

Answer 35

flux of matter down a concentration gradient

Question 36

How do we calculate diffusion flux

Answer 36

J = -DdC/dz J - diffusion flux D - diffusion coefficient dC/dx - concentration gradient

Question 37

Describe the characteristics of gas diffusion

Answer 37

increases slowly with temperature

Question 38

Describe diffusion in liquids and what it depends on

Answer 38

Increases with temperature Depends on viscosity and hydrodynamic radius

Question 39

Define mobility

Answer 39

mobility refers to the ability of a particle, molecule, or ion to move within a medium under the influence of a driving force

Question 40

What happens when a force f acts on an ion

Answer 40

when a force f acts on an ion it accelerates in the direction of the force, the force is determined by the electric friend and the charge on the ion

Question 41

How do we calculate f elec

Answer 41

felec = zieE zie - charge on the ion E - electric field

Question 42

How do we calculate f frag

Answer 42

f drag = 6πηaS

Question 43

How do we calculate the velocity when the f drag and f elec balance

Answer 43

s = zieE/6πηa = ui ui - mobility of the ion

Question 44

What is waldens rule

Answer 44

waldens rule is a useful rule of thumb which says that the product of conductivity and viscosity is approximately constant