Physical Chemistry

Front 1

What is a Bronsted Lowry Acid?

Back 1

A Species with a tendency to lose a proton(donates it)

Front 2

What is a Bronsted Lowry base?

Back 2

A species with a tendency to gain a proton(accepts it)

Front 3

Is it the same as Lewis theory?

Back 3

No, the Lewis theory concerns electron pairs.

Front 4

How is it expressed?

Back 4

Acid *double arrows* H+ + conjugate base (acid without H+)

Front 5

When does the acid yield a H+?

Back 5

When a conjugate base is present or when it can form in order to accept H+.

Front 6

Do Acids and Bases have to be neutral?

Back 6

No, they can be ions.

Front 7

Give the 2 types of acid and define them?

Back 7

Strong acid- strong electrolytes in general completely dissociate in solution and hence donate all of their protons.

Weak acid- weak electrolytes do not completely dissociate in solution.

Front 8

Show a general acid-base eqm?

Back 8

Front 9

What if an acid is strong what effect?

Back 9

The conjugate base is weak.

Front 10

Write down the expression of Acid eqm with water and base eqm with water?

Back 10

Front 11

What is the ionic product of water?

Back 11

When 2 molecules of water dissociate with one acting as the acid and one as the base.

Front 12

What is significant about ionic product of water?

Back 12

Even the most purified water possesses residual conductivity due to the eqm.

Front 13

What does the Ionic product of water indicate?

Back 13

That water is amphiprotic which means it can gain or lose a proton so it can act as both acid and base.

It is an autoprotolysis reaction which occurs when a proton is transferred between 2 identical molecules.

Front 14

Express the ionic product of water in terms of Keq?

Back 14

Products/reactants, you then eliminate a water from top and bottom, and then replace them with respect to activity.

Front 15

Describe the degree of ionisation for Ionic product of water?

Back 15

It is very small and therefore equal to 1 as the activity of a pure liquid is 1.

Therefore keq will acc be [H+] [OH-]

Front 16

Why is the ionic product of water defined Kw?

Back 16

[H2O] is constant in pure water and dilute aqueous solutions as it is large so the ionic product of water is defined as such. It is equal to 1x 10^-14.

Front 17

What is the concentration of H+ and OH- in pure water?

Back 17

1x10^-7 as they are equal and maintain a charge balance. If Kw is less than that for H+ then the solution is basic and vice versa.

Front 18

What is pH?

Back 18

Hydrogen ion exponent, you know it equals to lol.

Front 19

Can pH values fall outside the 1-14 range

Back 19

Yes, for acids and bases stronger than 1M in concentration.

Front 20

Express Kw in terms of pH?

Back 20

-logKw= -log [H+] + -log [OH-]

14= pH + pOH

Front 21

How do you express weak acid and base dissociation constants?

Back 21

Products over reactants.

Also the bigger the ka or kb(the weaker the acid basically) the smaller the pka or pkb.

Front 22

What are salts divided into?

Back 22

4 according to their acid/base derivation:

Strong acid and base- KCl

Strong acid weak base- NH3Cl

Weak acid strong base- Sodium Ethanoate

Weak acid weak base- ammonium methanoate

Front 23

Explain parameter of Strong acid and strong base salt?

Back 23

1. Break them down to their respective oppositely charged parts.

2. Match them with H+ and OH- from water

3. Now you know whether they are a strong acid and strong base

4. They form a neutral solution

Front 24

Explain the parameters of weak acid and strong base?

Back 24

Same steps as before to identify whether they are weak or strong.

There is an excess of OH- as H+ associates with the weak acid anions, and the solution is alkaline.

Front 25

Explain the parameters of S acid and W base?

Back 25

Same as the last one, this time solution is acidic.

Front 26

Explain the parameters of W acid and W base?

Back 26

Both will interact with water and the solutions pH depends on the dissociation constants of both.

Ka=kb means neutral and so on.

Front 27

What is a buffer solution?

Back 27

An acidic(or basic) buffer consists of a W acid(or base) mixed with one of its salts(conjugate).

It resists changes in pH when small amounts of acid or base are added.

Front 28

Why is a buffer solution able to do that?

Back 28

Ration between concentration of HA and A- does not vary much.

[H+]= [acid]/[salt] x ka

Front 29

What is Henderson-Hasselbalch equation?

Back 29

pH= pKa + log ( [salt]/[acid])

And for a mixture containing equal amounts of HA and A- pH is equal to pKa.

Front 30

What is a Half neutralised buffer solution?

Back 30

Follows Le chateliers principle.

Front 31

What is electrolysis?

Back 31

Chemical effect of passing an electric current through a solution.

Front 32

What is an electrolyte?

Back 32

A solute which when dissolved in a suitable solvent yields a solution which conducts electricity.

Front 33

What is an ion?

Back 33

An atom,molecule or fragment bearing a residual electric charge.

Front 34

What is an electrode? Give the 2 types?

Back 34

1 of 2 or more conducting pathways from a source of current to a solution.

Anode- electrode towards which the anions migrate.

Cathode- electrode towards which the cations migrate.

Front 35

What is Ohm's law?

Back 35

Pd in volts across a conductor is = current flowing through the conductor x resistance.

Kgm-1S-3A-2

Front 36

What is Potential difference?

Back 36

Work done when 1 coulomb of charge passes through the points.

V= W/Q

Front 37

What is a coulomb?

Back 37

Amount of charge transported by a constant current of one ampere in one second.

1C= 6.242 x 10 to the 18 protons.

Front 38

What is resistivity?

Back 38

How easily a material allows current through.

P= R X A/L Units are horseshoe meters

Current rises as A rises and drops as L Rises

Front 39

What is Conductance?

Back 39

The inverse of resistance.

G= 1/R units are S

Front 40

What is conductivity?

Back 40

Conductance multiplied by cell constant.

S x m-1 units

Front 41

What does conductivity depend on?

Back 41

Number of ions in solution, but not proportional to concentration. The same applies for conductance.

Front 42

What is molar conductivity?

Back 42

Conductivity of a solution/ concentration

Units are SM2Mol-1

Front 43

How to draw a molar conductivity graph? And what is it used for?

Back 43

Molar conductivity of Y-axis. Square root C on x axis.

Used to distinguish between weak(goes down curved) and strong (linear decrease) electrolytes

Front 44

What is ion migration?

Back 44

Movement by an electric field.

Front 45

What is ion mobility?

Back 45

How electrolytes move through the solvent.

Either by diffusion or migration.

Front 46

What are the types of interactions?

Back 46

Ion-Ion interactions and ion-solvent interactions.

Front 47

What is Ion-Ion interactions?

Back 47

Intiates from electrostatic interactions between ions of opposing charges which can produce 2 things:

1. Ion pairing

2. Ionic atmosphere

Front 48

What is ion pairing?

Back 48

It occurs transiently meaning as soon as they are within range and they form neautral species and is strongest for small,higher charged ions and higher concentrations.

Front 49

What is ionic atmosphere?

Back 49

Constantly in flux meaning that on avg an ion of a certain charge will have more ions around it of the opposite charge forming a cloud of oppositely charged species.

Front 50

Does the ionic atmosphere stay like that?

Back 50

No, when a charge is applied they begin to move to the oppositely charged electrode.

Front 51

What is ion solvent interaction?

Back 51

Ion-dipole interactions where water is the key solvent, hydration shells are formed due to the charged nature of ions and classified as either primary or secondary shells.

Front 52

How do ion-ion Interactions fair with a strong electrolyte?

Back 52

In an infinitely dilute solution there would be no ion-ion interactions to affect ion mobility. This is limiting molar conductivity.

Front 53

How do Ion-solvent interactions fair with strong electrolytes?

Back 53

An electrophretic effect occurs meaning the symmetry effect between the moving ion and the oppositely charged ions acting as a dragnet. The solvent molecules also get dragged but in the opposite direction causing friction and then ions slow down.

Front 54

What is the kohlrausch law? and when is it used?

Back 54

Molar conductivity= limiting molar conductivity - (experimental constant x root conc)

Used for strong electrolytes at moderate concentrations.

Front 55

What did Kohl discover?

Back 55

That at RT the Limiting MC values for pairs of salts having a common ion was approx. 0.

He also said MC was the sum of contributions in terms of the number of cations/anions and limiting MC of each pair.

Front 56

Why is Kohl's law useful?

Back 56

Helps us estimate limiting MC values for weak electrolytes, and this is done utilising their salts which would be considered strong electrolytes.

Front 57

What is the Arrhenius Ionisation theory?

Back 57

Solutions of electrolytes exist in eqm between undissociated solute molecules and fully dissociated ions.

For weak electrolytes the Degree of dissociation= molar conductivity/ limiting molar conductivity.

Front 58

What are the 2 extremes in dissociation?

Back 58

Highly concentrated acidic solution, little water present hardly any dissociates.

Infinitely dilute- fully dissociates as both LMC and MC are equal (weak electrolytes decrease rapidly with concentration).

Front 59

What are the Ostwald equations?

Back 59

Eqm constant= (MC squared x C) / LMC(LMC-MC)

Front 60

What would happen if electrolytes spontaneously ionise?

Back 60

Attraction of opposite charges would make them immediately recombine.

Front 61

What is Er?

Back 61

Dielectric constant, the factor by which the electric charge between 2 point charges is reduced relative to that in a vacuum.

Front 62

What counterbalances the result in the overall speed?

Back 62

2 factors, electric force of the applied field and frictional force.

Front 63

What is the applied electric field?

Back 63

Fa (accelaration force) = Z (charge number) e (charge on electron) E (field strength)

Front 64

What is Stokes law?

Back 64

Fr (frictional viscous drag) = 6pie n ( medium viscosity) aV (radius of the ion) d (drift velocity)

Front 65

What 2 factors govern conduction?

Back 65

2 factors when there's no inter-ionic interactions and they are:

1. Concentration of mobile charges

2. Mobility of charge carriers

Front 66

What is the Grotthuss mechanism?

Back 66

The mobility of H+ and OH- ions in water at RT is incredibly fast, H+ is specially fast is strongly solvated solutions.

Front 67

What is this high Mobility due to?

Back 67

Proton transfer between hydronium and H+ in water and vice versa with hydroxyl and OH-

This is what we call the grotthuss mechanism.

Front 68

What happens at very low t?

Back 68

Quantum tunneling effect occurs and it is more significant for lighter,smaller ions.

Front 69

What is an activity coefficient?

Back 69

A measure of non-ideality of mixing.

Front 70

What do activity coefficients depend on?

Back 70

Size of ion

Composition of the solution

Temperature

As the solute is more dilute it becomes 1

Front 71

What is the case in a non-ideal solution?

Back 71

Due to interactions of the solute with other species which becoming likely to reduce its availability which is not the case at very high concentrations.

Front 72

What does the debye-huckel theory describe?

Back 72

Behaviour of strong electrolytes in solution.

Front 73

What does the DH theory presume?

Back 73

Strong electrolytes completely dissociate into ion.

Non-ideality is due to electrostatic interactions

Front 74

What is the main problem with DH theory?

Back 74

Estimating the extra free energy that arised from the interactions.

Front 75

What does an electrochemical cell consist of?

Back 75

2 or more electrodes(metallic) immersed in an electrolyte (it may be in solution,liquid or solid)

Front 76

What is the anode?

Back 76

Negative terminal of a galvanic cell(oxidation occurs here)

Front 77

What is a galavanic cell?

Back 77

A cell that produces electricity as a result of a spontaneous reaction.

Front 78

What is an electrolytic cell?

Back 78

A cell that requires an external source of electricity to drive a non-spontaneous reaction.

Front 79

What does an electrode compartment consist of?

Back 79

One electrode and its accompanying electrolyte or both electrodes if they have the same electrolyte.

A single electrode compartment with one electrode consists a 'half-cell'.

Front 80

What happens if the electrolytes differ?

Back 80

The 2 compartments are joined by a semi-permeable membrane or salt bridge.

Front 81

How are the components in a cell?

Back 81

Either in physical or electrical contact or both.

Front 82

How are these differences indicated?

Back 82

If they are in direct contact we use a | separator

And if separated by a semi permeable membrane we use a 3 dotted line

And if separated by a salt bridge then a || line is used

Front 83

What is that cell notation known as?

Back 83

Cell diagram with left hand side showing oxidation and right hand side showing reduction.

Front 84

Briefly state different electrodes?

Back 84

Ion-ion electrodes- half reactions which involve only ionic species.

Electrons must be supplied and removed from the system by a solid electrical conductor. Usually Pt as it is inert.

Pt is written at the start of the cell diagram. And no phase changes are denoted by a comma.

Front 85

Give some important points about cell diagrams?

Back 85

Substance losing electrons is written closest to the metal electrode.

The most oxidised species are written furthest away from the metal electrode.

Front 86

Another type of electrode?

Back 86

Gas which occur for half reactions which involve a gas.

Pt is used here too.

Front 87

How is a general cell diagram written?

Back 87

Starting from the left(anode):

1. Reactive/inert metal electrode

2. Solution of metal ions/redox couple

3. Salt bridge

4. Same as 2

5. Same as 1

Front 88

How do cells work?

Back 88

Driving force in a cell series arises from a decrease in free energy.

This comes from:

1. A chemical reaction

2. Physical change

Front 89

What is electromotive force?

Back 89

Voltage developed by a source of electrical energy.

Front 90

What is a liquid junction potential?

Back 90

When a difference in [ ] and mobility of ions exists at an interface between 2 ionic solutions.

Front 91

How is a LJP minimised?

Back 91

By a salt bridge that uses a salt like KCl where the mobilities of each proponents are almost the same.

Front 92

What does the EmF of a cell depend on?

Back 92

The two ion concentrations x and y

The molalities (amount of substance in a specified mass of solvent) of the 2 solutions are 1 mol kg-1

Front 93

How is the pd of a cell written?

Back 93

E= Er-EL

Front 94

Briefly explain the calomel electrode?

Back 94

Hg(l) | Hg2Cl2 (s) | Cl-(sat)

The 2 mercuries are covered with a saturated KCl solution.

It is slow and very T sensitive.

Front 95

Key features of standard potential?

Back 95

Always positive, always written as reduction potential, not affected by changes in stoichiometry.