mistakes

Question 1

The splitting of the d orbitals in an octahedral crystal field can be described as follows:

Answer 1

The d orbitals split into two sets with an energy difference
AND
The dxy , dzy and dxz orbitals are lower in energy than the dx2-y2 and dz2 orbitals; [1]

Question 2

energy gap in degenerate orbitals of ligand atom corresponds to

Answer 2

light in the visible region of the spectrum

Question 3

how can polarimeters be used to determine the relative proportion of two enantiomers

Answer 3

• plane-polarized light passed through sample
• find angle of rotation of pure enantiomers
• measure angle of rotation of mixture
• mixture has angle between that of two enantiomers
• ratio of angles gives purity

Question 4

describe how ionising radiation destroys cancer cells

Answer 4

• errors in DNA sequences
• cancer cells more susceptible
• prevents cancer cells from growing/multiplying

Question 5

describe how fractional distillation

Answer 5

• compounds have different boiling points
• temperature decreases upwards
• component with lower boiling point leaves first

Question 6

outline why colours of flame tests are different

Answer 6

• electrons promoted and fall back down to lower energy levels
• energy difference between energy levels is different
• frequency of colour emitted different

Question 7

benzene + chlorine

Answer 7

C6H5Cl + HCl

Question 8

enthalpy of condensation from gas to liquid

Answer 8

exothermic

Question 9

example of NH3 acting as a Bronsted Lowry acid and base

Answer 9

Nh3 + H+ -> NH4+
NH3 + BF3 -> H3NBF3

Question 10

c = vλ

Answer 10

c = speed of light
v = frequency of light
λ = wavelength of light

Question 11

E = hv

Answer 11

energy
planck’s constant
v = frequency of light

Question 12

y axis of Maxwell Boltzmann

Answer 12

fraction of particles

Question 13

why use the pH scale instead of [H+]?

Answer 13

converts a wide range of H+ into a simple scale/numbers between 1 and 14

Question 14

Cu electron config

Answer 14

4s13d10

Question 15

(i) State the type of bond fission that takes place in a SN1 reaction.

Answer 15

heterolytic

Question 16

(iv) Suggest, giving a reason, the percentage of each isomer from the SN1 reaction. [2]

Answer 16

similar/equal percentages ✔

nucleophile can attack from either side «of the planar carbocation» ✔

Question 17

Nitrobenzene, C6H5NO2, can be converted to phenylamine via a two-stage reaction.

Formulate the equation for each stage of the reaction.

Answer 17

Stage one:
C6H5NO2 (l) + 3Sn (s) + 7H+ (aq) -> C6H5NH3 (aq) + 3Sn2 (aq) + 2H2O (l) ✔
Stage two:
C6H5NH3+ (aq) + OH- (aq) -> C6H5NH2 (l) + H2O (l) ✔

Question 18

does confirmation of the rate expression prove a mechanism?

Answer 18

no, different mechanisms could give the same rate expression

Question 19

Sn2

Answer 19

gives inversion of configuration (almost 100%)

Question 20

why do lines on the hydrogen emission spectrum converge?

Answer 20

at higher energy, the energy levels are much closer together

Question 21

why electroplating?

Answer 21

corrosion protection/resistance
shiny appearance

Question 22

why is the ideal gas law not always accurate?

Answer 22

assumption that gas particles have negligible volume and no forces act between them (high pressure and low temperatures)

Question 23

how to calculate absolute uncertainty

Answer 23

relative uncertainty/100 x measured value

Question 24

look over the different forms of isomerism

Question 25

suggest one reason why the calculated value of dH using Hess' law may be considered accurate and one why it can be considered approximate

Answer 25

Hess’s law is a statement of conservation of energy OR method is based on a law values were experimentally determined/had uncertainties

Question 26

suggest two advantages of understanding organic reaction mechanisms

Answer 26

choose an appropriate reaction for preparing a target compound control/predict «desired» products to make (retro)synthesis more effective

Question 27

an advantage of TAT and an example of a cancer that is commonly treated by this method

Answer 27

selectively destroys cancer cells/no damage to healthy cells breast cancer

Question 28

Mg(OH)2 is

Answer 28

solid

Question 29

identify examples of two types of medical radioactive waste and how each must be treated for proper disposal

Answer 29

LLW (eg gowns/protective clothing): storage «in shielded container» until isotope has decayed/for a period of time «then dispose as non-radioactive waste» radioactive sources/ equipment (intermediate/medium level waste/ILW/MLW): storage «in shielded container in concrete chambers» underground/in caves

Question 30

explain the increase in the molecular dipole moment as one chlorine atom in CCl4 is replaced with fluorine to produce CCl3F

Answer 30

- fluorine more electronegative than chlorine - sum of bond polarities is non-zero/greater

Question 31

outline what is meant by the term ring strain

Answer 31

bond angles of the C-N bonds are 90 instead of 109.5/120 so cause instability

Question 32

why may extra side chains enable antibiotics to retain their activity

Answer 32

side chains react with penicillinase acting as suicide substrates and inhibitors

Question 33

why isolation of crude product of reaction of salicylic aid + ethanoic anhydride involved addition of ice-cold water

Answer 33

speeds crystallisation as aspirin has low solubility in water at low temperatures

Question 34

identify site of action of omeprazole and esomeprazole in the body

Answer 34

proton pump

Question 35

describe how gas chromatography enables the components of urine to be analysed

Answer 35

- components have different affinities for, and partition between, the 2 phases - the mobile and stationary phase - therefore, they move at different rates through instrument (have different retention times)

Question 36

percentage experimental yield

Answer 36

actual yield/theoretical yield x 100

Question 37

why does sulphuric acid provoke a greater temperature change for neutralisation

Answer 37

it is diprotic

Question 38

suggest why scientists often make assumptions that do not correspond to reality

Answer 38

simplifies the calculations involved

Question 39

state and explain the action of opiates as painkillers

Answer 39

- bind to opioid receptors - suppress/blocks transmission of pain impulses to cns - resemble endorphins

Question 40

some mild analgesic contain a solid mixture of acidic aspirin and a non-acidic organic chemical of similar polarity to aspirin. discuss how acid-base properties and the process of solvent extraction can be used to separate aspirin from the mixture

Answer 40

- dissolve compounds in an organic solvent - add NaOh to produce the water-soluble sodium salt of aspirin - separate the two immiscible layers - convert the salt back to aspirin by reacting with acid, H+

Question 41

state a green solution to the problem of organic solvent waste

Answer 41

recycle the solvents or catalysis that leads to better/higher yield or use water as solvent

Question 42

equation for the buffer formed by CO2 and the HCO3- ion

Answer 42

H2O + CO2 (H2CO3) <-> H+ + HCO3- so HCO3- is the conjugate base [A-] and CO2 is the acid [HA]

Question 43

explain the effect of a large amount of aspirin on the pH of blood

Answer 43

pH decreases. the H+ produced from aspirin reacts with HCO3-, producing CO2 and water.

Question 44

outline how green chemistry was used to develop the precursor for oseltamivir

Answer 44

- genetically modified E.Coli - biosynthesis - cells of the bacteria are broken down to form shikimic acid

Question 45

describe the terms in Nt=N0(0.5)^t/k

Answer 45

Nt = amount left N0= amount at start t = time k = half life/decay constant

Question 46

equations for anode and cathode of breathalyser

Answer 46

C2H5OH + H2O -> CH3COOH + 4H+ + 4e- O2 + 4H+ + 4e- -> 2H2O

Question 47

outline how codeine can be synthesised from morphine

Answer 47

react with CH3I/methyl iodide in alkaline solution

Question 48

compare, giving a reason, the bond enthalpies of the O to O bonds in O2 and O3

Answer 48

bond in O3 has lower enthalpy because bond order is 1.5 not 2

Question 49

formula for IHD

Answer 49

IHD = 1/2 (2C+2+N-H-X).

Question 50

draw the lewis structure of ozone

Answer 50

dative bond

Question 51

bond angle of ozone molecule

Answer 51

110

Question 52

how to determine the wavelength of light absorbed by a single molecule of something

Answer 52

divide the bond enthalpy by Avogadro's number - this gives you E E=hv

Question 53

BOD after 5 days

Answer 53

oxygen conc on day 1 - oxygen conc on day 5

Question 54

what does a Ka smaller than 1 mean?

Answer 54

weak acid

Question 55

state the feature of Taxol that is a major challenge in its synthesis

Answer 55

it contains numerous stereocentres/chiral carbons

Question 56

more detailed on detection of steroids in blood and urine

Answer 56

1. sample/liquids vaporized at high temperature 2. sample injected into mobile phase/inert gas 3. nitrogen/helium/inert gas acts as mobile phase, carrying the sample through the column 4. stationary phase consists of a packed column 5. components are separated by partition between mobile phase and stationary phase as components have different retention times 6. there is a detector at the end of the column (Mass Spectrometer) 7. databases/library of known fragmentation patterns can be used

Question 57

does the chlorine atom or chloride ion have a greater radius

Answer 57

chlorine ion - has an extra electron so more electron–electron repulsion

Question 58

in the titration between ethanoic acid and sodium hydroxide, what are the major species, other than water and sodium hydroxide at: - buffer region - equivalence point

Answer 58

CH3COO- and CH3COOH CH3COO-/CH3COONa

Question 59

for a mechanism to be possible, it needs to

Answer 59

match the experimental rate law

Question 60

state and explain the relative solubility of codeine in water compared to morphine and diamorphine

Answer 60

- morphine > codeine > diamorphine in terms of solubility in water - stronger H bonding due to more hydroxyl groups leads to greater solubility

Question 61

equation for vapour pressure

Answer 61

vapour pressure of solution = mole fraction of solvent x vapour pressure of the solvent

Question 62

raoult's law

Answer 62

P = PA + PB

Question 63

discuss the properties that make a radioisotope suitable for diagnosis

Answer 63

- easily detected/same frequency as X rays - short/intermediate half life so does not remain in the body for a long time - weak ionising radiation - chemically binds to many biologically active compounds

Question 64

large percentage error means

Answer 64

large systematic error in procedure

Question 65

small percentage uncertainty means

Answer 65

small random errors

Question 66

explain the development of resistant virus strains in the presence of antiviral drugs

Answer 66

- viruses undergo rapid mutation - drug no longer binds to virus

Question 67

suggest a reason for using a phosphate salt of oseltamivir in oral tablets

Answer 67

more soluble in water

Question 68

how to use extrapolation to determine the maximum temperature

Answer 68

start of reaction intersects extrapolated line assumption: the reaction is instantaneous