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mistakes 2 Flashcards

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1
Q

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

A

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]

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2
Q

energy gap in degenerate orbitals of ligand atom corresponds to

A

light in the visible region of the spectrum

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2
Q

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

A
  • 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
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3
Q

describe how ionising radiation destroys cancer cells

A
  • errors in DNA sequences
  • cancer cells more susceptible
  • prevents cancer cells from growing/multiplying
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4
Q

describe how fractional distillation

A
  • compounds have different boiling points
  • temperature decreases upwards
  • component with lower boiling point leaves first
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5
Q

outline why colours of flame tests are different

A
  • electrons promoted and fall back down to lower energy levels
  • energy difference between energy levels is different
  • frequency of colour emitted different
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6
Q

benzene + chlorine

A

C6H5Cl + HCl

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7
Q

enthalpy of condensation from gas to liquid

A

exothermic

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8
Q

example of NH3 acting as a Bronsted Lowry acid and base

A

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

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9
Q

c = vλ

A

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

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10
Q

E = hv

A

energy
planck’s constant
v = frequency of light

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11
Q

y axis of Maxwell Boltzmann

A

fraction of particles

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12
Q

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

A

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

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13
Q

Cu electron config

A

4s13d10

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14
Q

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

A

heterolytic

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15
Q

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

A

similar/equal percentages ✔

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

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16
Q

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

Formulate the equation for each stage of the reaction.

A

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

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17
Q

does confirmation of the rate expression prove a mechanism?

A

no, different mechanisms could give the same rate expression

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18
Q

Sn2

A

gives inversion of configuration (almost 100%)

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19
Q

why do lines on the hydrogen emission spectrum converge?

A

at higher energy, the energy levels are much closer together

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20
Q

why electroplating?

A

corrosion protection/resistance
shiny appearance

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21
Q

why is the ideal gas law not always accurate?

A

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

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22
Q

how to calculate absolute uncertainty

A

relative uncertainty/100 x measured value

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23
Q

look over the different forms of isomerism

A
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24
Q

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

A

Hess’s law is a statement of conservation of energy OR method is based on a law

values were experimentally determined/had uncertainties

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25
Q

suggest two advantages of understanding organic reaction mechanisms

A

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

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26
Q

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

A

selectively destroys cancer cells/no damage to healthy cells

breast cancer

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27
Q

Mg(OH)2 is

A

solid

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28
Q

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

A

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

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29
Q

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

A
  • fluorine more electronegative than chlorine
  • sum of bond polarities is non-zero/greater
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30
Q

outline what is meant by the term ring strain

A

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

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31
Q

why may extra side chains enable antibiotics to retain their activity

A

side chains react with penicillinase acting as suicide substrates and inhibitors

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32
Q

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

A

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

33
Q

identify site of action of omeprazole and esomeprazole in the body

A

proton pump

34
Q

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

A
  • 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)
35
Q

percentage experimental yield

A

actual yield/theoretical yield x 100

36
Q

why does sulphuric acid provoke a greater temperature change for neutralisation

A

it is diprotic

37
Q

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

A

simplifies the calculations involved

38
Q

state and explain the action of opiates as painkillers

A
  • bind to opioid receptors
  • suppress/blocks transmission of pain impulses to cns
  • resemble endorphins
39
Q

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

A
  • 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+
40
Q

state a green solution to the problem of organic solvent waste

A

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

41
Q

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

A

H2O + CO2 (H2CO3) <-> H+ + HCO3-

so HCO3- is the conjugate base [A-] and CO2 is the acid [HA]

42
Q

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

A

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

43
Q

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

A
  • genetically modified E.Coli
  • biosynthesis
  • cells of the bacteria are broken down to form shikimic acid
44
Q

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

A

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

45
Q

equations for anode and cathode of breathalyser

A

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

46
Q

outline how codeine can be synthesised from morphine

A

react with CH3I/methyl iodide in alkaline solution

47
Q

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

A

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

48
Q

formula for IHD

A

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

49
Q

draw the lewis structure of ozone

A

dative bond

50
Q

bond angle of ozone molecule

A

110

51
Q

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

A

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

52
Q

BOD after 5 days

A

oxygen conc on day 1 - oxygen conc on day 5

53
Q

what does a Ka smaller than 1 mean?

A

weak acid

54
Q

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

A

it contains numerous stereocentres/chiral carbons

55
Q

more detailed on detection of steroids in blood and urine

A
  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
56
Q

does the chlorine atom or chloride ion have a greater radius

A

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

57
Q

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

A

CH3COO- and CH3COOH
CH3COO-/CH3COONa

58
Q

for a mechanism to be possible, it needs to

A

match the experimental rate law

59
Q

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

A
  • morphine > codeine > diamorphine in terms of solubility in water
  • stronger H bonding due to more hydroxyl groups leads to greater solubility
60
Q

equation for vapour pressure

A

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

61
Q

raoult’s law

A

P = PA + PB

62
Q

discuss the properties that make a radioisotope suitable for diagnosis

A
  • 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
63
Q

large percentage error means

A

large systematic error in procedure

64
Q

small percentage uncertainty means

A

small random errors

65
Q

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

A
  • viruses undergo rapid mutation
  • drug no longer binds to virus
66
Q

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

A

more soluble in water

67
Q

how to use extrapolation to determine the maximum temperature

A

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

68
Q

why might true enthalpy change be different from calculated value from bond energies

A

bond energies are average values, not specific to the compound

69
Q

Explain why aspirin is not stored in a hot, humid location.

A

water causes hydrolysis/conversion back into salicylic acid

heat increases the rate of hydrolysis

70
Q

Taxol was originally obtained from the bark of the Pacific yew tree.
Outline how Green Chemistry has improved the process of obtaining Taxol.

A

stripping the bark kills Pacific yew tree.
Taxol is now produced semi-synthetically/Taxol from 10-DAB/10-deacetylbaccatin, using the leaves of European yew.

This new process has also eliminated a large propoertion of hazardous waste.

71
Q

TAT

A
  • alpha emitter attached to carrier drug/protein
  • absorbed by cancer/growing cells
  • alpha particles have high ionizing power/low penetrating power
  • selectively destroys cancer cells, affecting healthy cells much less
72
Q

Suggest why the end point of a starch-iodine titration is difficult to determine, even with the addition of starch to turn the remaining free iodine black.

A

release of iodine from starch-iodine complex is slow so titration must be done slowly

73
Q

mechanism by which chiral auxiliaries force a reaction to be carried out asymmetrically

A

stereochemical induction

74
Q

units for Ea

A

J/mol or kJ/mol

75
Q

Explain why a colorimeter set at a wavelength of 500nm is not suitable to investigate
reactions of Zn2+
compounds. Use section 3 of the data booklet.

A
  • Zn2+ does not form coloured compounds/ has a complete d subshell/orbital
  • 500 nm is in visible region so no absorbance will be seen
76
Q

chemical test to distinguish between strong and weak acid

A

add hydroxide
higher temperature rise with stronger acid

77
Q

define a homologous group

A

compounds of the same family with the general formula

78
Q

percentage error

A

Va-Ve/Ve ABSOLUTE

79
Q
A

ib chemistry (29 decks)

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