Advanced Higher Chemistry Unit 2

Front 1

What is a standard solution?

Back 1

A solution of an accurately known concentration.

Front 2

What are the characteristics of a primary standard?

Back 2

- Available in a high state of purity

- Stable when solid and when in solution

- Soluble in water

- Has a reasonably high percentage mass to reduce percentage errors when weighing

Front 3

How is a standard solution made up?

Back 3

Weigh out the primary standard and dissolve in deionised water. Transfer the solution and rinsings to a standard flask and make it up to the mark with more deionised water.

Front 4

What is the end-point?

Back 4

When a colour change occurs in the presence of an indicator.

Front 5

What is the equivalence point?

Back 5

When the reaction is just complete.

Front 6

What happens during a redox titration?

Back 6

An oxidising agent reacts with a reducing agent.

Front 7

What is a complexometric titration?

Back 7

A titration that involves the formation of a complex such as EDTA.

Front 8

What is gravimetric analysis?

Back 8

A form of analysis where the measurements are masses determined using a balance. The mass of an element or compound present is found by changing that substance into another of known chemical composition that can be readily isolated, purified and weighed.

Front 9

What is dynamic equilibrium?

Back 9

When the rate of the forward reaction is equal to the rate of the reverse reaction. The concentration of the reactants and products are constant but not necessarily equal.

Front 10

How does a catalyst affect equilibrium?

Back 10

Speeds up the rate at which equilibrium is reached but does not affect its position.

Front 11

What is the general equation for the equilibrium constant?

Back 11

aA + bB ->/<- cC +dD

K = [C]^c x [D]^d / [A]^a x [B]^b

Front 12

What is homogeneous equilibrium?

Back 12

When all the species are in the same phase.

Front 13

What is heterogeneous equilibrium?

Back 13

When the species present are in more than one phase.

Front 14

What is Le Chatelier's Principle?

Back 14

When a reaction at equilibrium is subjected to a change the composition alters in such a way as to minimise the effects of that change.

Front 15

For an endothermic reaction, an increase in temperature favours the _________ and K _________.

Back 15

Products, increases.

Front 16

For an exothermic reaction, an increase in temperature favours the __________ and K _________.

Back 16

Reactants, decreases.

Front 17

What are immiscible liquids?

Back 17

Liquids which do not mix together.

Front 18

What is partitioning?

Back 18

When a solute dissolves partially in each of two (or more) immiscible liquids.

Front 19

What happens when the solute partitions itself?

Back 19

A dynamic equilibrium is established wherein some of the solute in the lower layer moves to the upper layer and vice versa.

Front 20

What is the partition coefficient?

Back 20

The equilibrium constant that stipulates that a particular solute will always partition itself between the same two solvents in the same ratio.

Front 21

What is a solvent extraction?

Back 21

The technique used to extract and purify a desired product from a reaction mixture using a separating funnel.

Front 22

What is a solvent extraction dependent on?

Back 22

The desirable solute being more soluble in one liquid solvent than another.

Front 23

How can solvent extraction be used most efficiently?

Back 23

By using many smaller quantities of solvent a few times rather than the same total volume once only.

Front 24

In chromatography, what is the R1 value?

Back 24

The distance traveled relative to the solvent.

Front 25

What is the expression for R1?

Back 25

R1 = distance traveled by compound / distance traveled by solvent

Front 26

How can R1 be used?

Back 26

Different compounds have different R1s.

Front 27

What can an acid also be known as?

Back 27

A proton donor.

Front 28

What can a base also be known as?

Back 28

A proton acceptor.

Front 29

What is formed when an acid loses a proton?

Back 29

A conjugate base.

Front 30

What is formed when a base accepts a proton?

Back 30

A conjugate acid.

Front 31

What is the equation for the ionisation of water?

Back 31

H20 (l) (acid) + H2O (l) (base) ->/<- H3O+ (aq) (conjugate acid) + OH- (aq) (conjugate base)

Front 32

In terms of log, what is the equation for pH?

Back 32

pH = -log[H+]

Front 33

What is a monoprotic acid?

Back 33

An acid that only donates one proton to an aqueous solution.

Front 34

How can the dissociation of a weak acid be represented?

Back 34

HA (acid) ->/<- H+ (conjugate acid) + A- (conjugate base)

Front 35

What is the dissociation constant of the acid, Ka?

Back 35

Ka = [H+][A-] / [HA]

Front 36

What is [H+] in a weak acid?

Back 36

[H+] = (square root of) Ka x c

Front 37

How can the dissociation constant be represented in terms of log?

Back 37

pKa = -logKa

pH = 1/2pKa - 1/2logc

Front 38

How does the value of Ka indicate acidity?

Back 38

The higher the value of Ka, the more acidic it is; the lower it is, the more basic it is.

Front 39

What are indicators?

Back 39

Usually weak acids in which the colour of the acid is different from its conjugate base.

Front 40

What is a buffer solution?

Back 40

One in which the pH remains constant when small amounts of acid or base are added.

Front 41

How does an acid buffer work?

Back 41

It consists of a solution of a weak acid and one of its salts. When an acid is added the H+ ions react with with the negative ions from the salt forming more acid molecules and the H+ concentration stays the same. When an alkali is added the OH- ions react with the H+ ions and acid ions dissociate to replace them. H+ concentration remains the same.

Front 42

How does a basic buffer work?

Back 42

It consists of a solution of a weak base and one of its salts. The weak base removes any added hydrogen ions and the conjugate acid replace any hydrogen ions removed when an alkali is added.

Front 43

What is the standard enthalpy of combustion?

Back 43

The energy given out when one mole burns completely in oxygen.

Front 44

What is the standard enthalpy of formation?

Back 44

The energy given out or taken in when one mole is formed from the elements in their standard states.

Front 45

What is calorimetry?

Back 45

The quantitative determination of a change in heat energy which occurs during a chemical reaction.

Front 46

What is Hess' Law?

Back 46

It states that the enthalpy change for a particular reaction depends only on the enthalpies of the starting reactants and of the products, but is independent of the route taken.

Front 47

Bond breaking is __________.

Back 47

Endothermic.

Front 48

Bond-making is ___________.

Back 48

Exothermic.

Front 49

Why are mean bond enthalpies used?

Back 49

Because the bond enthalpies of certain bonds can be different depending on what environment they're in.

Front 50

What is the Born-Haber cycle?

Back 50

A thermochemical cycle which is applied to the formation of an ionic compound.

Front 51

What are the steps of a Born Haber cycle (use formation of calcium iodide as an example)?

Back 51

1) Breaking down the Calcium metallic lattice. Enthalpy of atomisation (energy required to provide one mole of gaseous atoms)

2) Ionisation energies (first and second) of calcium.

3) Enthalpy changes of solid iodine to iodine ions - molar enthalpy of atomisation and the electron affinity (the enthalpy change when one mole of electrons is added to one mole of isolated atoms in the gaseous state).

Front 52

What is entropy?

Back 52

The measure of the disorder of a system, the higher the entropy the greater the disorder.

Front 53

What is the symbol of entropy?

Back 53

S

Front 54

What is the standard entropy of a substance?

Back 54

The entropy of one mole of the substance at a pressure of one atmosphere and a temp of 298K.

Front 55

What is the entropy of a substance at 0K (Third Law of Thermodynamics)?

Back 55

0

Front 56

What happens to the entropy of a substance as temp increases and the phases move from solid, to liquid, to gas?

Back 56

The entropy increases.

Front 57

What happens at a phase change from solid to liquid and from liquid to gas?

Back 57

There is a rapid increase in entropy.

Front 58

What is a feasible reaction?

Back 58

One that takes place of its own accord.

Front 59

What is the second Law of Thermodynamics?

Back 59

For a reaction to be feasible, the total entropy change for a reaction system and its surroundings must be positive (the entropy must increase).

Front 60

How can the standard free energy change give information about the position of equilibrium?

Back 60

deltaG < 0 then the forward reaction will be feasible so the products will predominate and vice versa.

Front 61

What is the electrode potential?

Back 61

The charge difference set up between a metal and the solution that it is in in an electrochemical cell.

Front 62

What is the pupose of a salt (ion) bridge?

Back 62

To allow ions to flow from one half cell to the other.

Front 63

What does the voltage found in an external circuit correspond to?

Back 63

The difference n the electrode potentials of the two half cells involved.

Front 64

What are the standard conditions in an electrochemical cell?

Back 64

- The concentration of the ions involved in the half reaction must be 1mol/l

- If gas is involved, it must be at a pressure of 1 atmosphere

- If temp. is not specified it is assumed to be 298K.

Front 65

How can the standard electrode potential of a half cell be measured?

Back 65

By linking it with a standard hydrogen half cell and measuring the voltage of the cell that is formed.

Front 66

How can the relative strengths of oxidising and reducing agents be found from their corresponding E values (standard electrode potentials)?

Back 66

The E value is a measure of how readily a species is reduced, the higher it is, the better an oxidising agent the substance in question will make.

Front 67

How is the standard free energy change related to the cell voltage or emf (E)?

Back 67

deltaG = -nFE where n is the number of moles of electrons transferred in the cell and F is the Faraday constant.

Front 68

What is the value of the Faraday constant?

Back 68

96,500

Front 69

What is a fuel cell?

Back 69

A cell that generates electricity directly from a redox reaction and works indefinitely as the reactants are constantly being added.

Front 70

What is the simplest fuel cell?

Back 70

The hydrogen fuel cell.

Front 71

When is a reaction first order?

Back 71

When the rate of reaction is directly proportional to the concentration of the reactant concerned.

Front 72

When is a reaction second order?

Back 72

When the rate of a reation is directly proportional to the square of the reactant concerned.

Front 73

How is the overall order of a reaction found?

Back 73

By adding the orders of the individual reactants.

Front 74

What is the rate equation?

Back 74

k = rate / [A]m[B]n...

Front 75

What is a reaction mechanism?

Back 75

The series of steps in a reaction.

Front 76

What is the overall rate of a reaction determined upon?

Back 76

The slowest step in the reaction mechanism, the rate-determining step.