mistakes 2 Flashcards
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]
2
Q
energy gap in degenerate orbitals of ligand atom corresponds to
A
light in the visible region of the spectrum
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
3
Q
describe how ionising radiation destroys cancer cells
A
- errors in DNA sequences
- cancer cells more susceptible
- prevents cancer cells from growing/multiplying
4
Q
describe how fractional distillation
A
- compounds have different boiling points
- temperature decreases upwards
- component with lower boiling point leaves first
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
6
Q
benzene + chlorine
A
C6H5Cl + HCl
7
Q
enthalpy of condensation from gas to liquid
A
exothermic
8
Q
example of NH3 acting as a Bronsted Lowry acid and base
A
Nh3 + H+ -> NH4+
NH3 + BF3 -> H3NBF3
9
Q
c = vλ
A
c = speed of light
v = frequency of light
λ = wavelength of light
10
Q
E = hv
A
energy
planck’s constant
v = frequency of light
11
Q
y axis of Maxwell Boltzmann
A
fraction of particles
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
13
Q
Cu electron config
A
4s13d10
14
Q
(i) State the type of bond fission that takes place in a SN1 reaction.
A
heterolytic
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» ✔
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) ✔
17
Q
does confirmation of the rate expression prove a mechanism?
A
no, different mechanisms could give the same rate expression
18
Q
Sn2
A
gives inversion of configuration (almost 100%)
19
Q
why do lines on the hydrogen emission spectrum converge?
A
at higher energy, the energy levels are much closer together
20
Q
why electroplating?
A
corrosion protection/resistance
shiny appearance
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)
22
Q
how to calculate absolute uncertainty
A
relative uncertainty/100 x measured value
23
Q
look over the different forms of isomerism
A
24
suggest one reason why the calculated value of dH using Hess' law may be considered accurate and one why it can be considered approximate
Hess’s law is a statement of conservation of energy OR method is based on a law
values were experimentally determined/had uncertainties
25
suggest two advantages of understanding organic reaction mechanisms
choose an appropriate reaction for preparing a target compound
control/predict «desired» products
to make (retro)synthesis more effective
26
an advantage of TAT and an example of a cancer that is commonly treated by this method
selectively destroys cancer cells/no damage to healthy cells
breast cancer
27
Mg(OH)2 is
solid
28
identify examples of two types of medical radioactive waste and how each must be treated for proper disposal
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
29
explain the increase in the molecular dipole moment as one chlorine atom in CCl4 is replaced with fluorine to produce CCl3F
- fluorine more electronegative than chlorine
- sum of bond polarities is non-zero/greater
30
outline what is meant by the term ring strain
bond angles of the C-N bonds are 90 instead of 109.5/120 so cause instability
31
why may extra side chains enable antibiotics to retain their activity
side chains react with penicillinase acting as suicide substrates and inhibitors
32
why isolation of crude product of reaction of salicylic aid + ethanoic anhydride involved addition of ice-cold water
speeds crystallisation as aspirin has low solubility in water at low temperatures
33
identify site of action of omeprazole and esomeprazole in the body
proton pump
34
describe how gas chromatography enables the components of urine to be analysed
- 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
percentage experimental yield
actual yield/theoretical yield x 100
36
why does sulphuric acid provoke a greater temperature change for neutralisation
it is diprotic
37
suggest why scientists often make assumptions that do not correspond to reality
simplifies the calculations involved
38
state and explain the action of opiates as painkillers
- bind to opioid receptors
- suppress/blocks transmission of pain impulses to cns
- resemble endorphins
39
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
- 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
state a green solution to the problem of organic solvent waste
recycle the solvents or catalysis that leads to better/higher yield or use water as solvent
41
equation for the buffer formed by CO2 and the HCO3- ion
H2O + CO2 (H2CO3) <-> H+ + HCO3-
so HCO3- is the conjugate base [A-] and CO2 is the acid [HA]
42
explain the effect of a large amount of aspirin on the pH of blood
pH decreases. the H+ produced from aspirin reacts with HCO3-, producing CO2 and water.
43
outline how green chemistry was used to develop the precursor for oseltamivir
- genetically modified E.Coli
- biosynthesis
- cells of the bacteria are broken down to form shikimic acid
44
describe the terms in
Nt=N0(0.5)^t/k
Nt = amount left
N0= amount at start
t = time
k = half life/decay constant
45
equations for anode and cathode of breathalyser
C2H5OH + H2O -> CH3COOH + 4H+ + 4e-
O2 + 4H+ + 4e- -> 2H2O
46
outline how codeine can be synthesised from morphine
react with CH3I/methyl iodide in alkaline solution
47
compare, giving a reason, the bond enthalpies of the O to O bonds in O2 and O3
bond in O3 has lower enthalpy because bond order is 1.5 not 2
48
formula for IHD
IHD = 1/2 (2C+2+N-H-X).
49
draw the lewis structure of ozone
dative bond
50
bond angle of ozone molecule
110
51
how to determine the wavelength of light absorbed by a single molecule of something
divide the bond enthalpy by Avogadro's number - this gives you E
E=hv
52
BOD after 5 days
oxygen conc on day 1 - oxygen conc on day 5
53
what does a Ka smaller than 1 mean?
weak acid
54
state the feature of Taxol that is a major challenge in its synthesis
it contains numerous stereocentres/chiral carbons
55
more detailed on detection of steroids in blood and urine
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
does the chlorine atom or chloride ion have a greater radius
chlorine ion - has an extra electron so more electron–electron repulsion
57
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
CH3COO- and CH3COOH
CH3COO-/CH3COONa
58
for a mechanism to be possible, it needs to
match the experimental rate law
59
state and explain the relative solubility of codeine in water compared to morphine and diamorphine
- morphine > codeine > diamorphine in terms of solubility in water
- stronger H bonding due to more hydroxyl groups leads to greater solubility
60
equation for vapour pressure
vapour pressure of solution = mole fraction of solvent x vapour pressure of the solvent
61
raoult's law
P = PA + PB
62
discuss the properties that make a radioisotope suitable for diagnosis
- 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
large percentage error means
large systematic error in procedure
64
small percentage uncertainty means
small random errors
65
explain the development of resistant virus strains in the presence of antiviral drugs
- viruses undergo rapid mutation
- drug no longer binds to virus
66
suggest a reason for using a phosphate salt of oseltamivir in oral tablets
more soluble in water
67
how to use extrapolation to determine the maximum temperature
start of reaction intersects extrapolated line
assumption: the reaction is instantaneous
68
why might true enthalpy change be different from calculated value from bond energies
bond energies are average values, not specific to the compound
69
Explain why aspirin is not stored in a hot, humid location.
water causes hydrolysis/conversion back into salicylic acid
heat increases the rate of hydrolysis
70
Taxol was originally obtained from the bark of the Pacific yew tree.
Outline how Green Chemistry has improved the process of obtaining Taxol.
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
TAT
- 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
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.
release of iodine from starch-iodine complex is slow so titration must be done slowly
73
mechanism by which chiral auxiliaries force a reaction to be carried out asymmetrically
stereochemical induction
74
units for Ea
J/mol or kJ/mol
75
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.
- 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
chemical test to distinguish between strong and weak acid
add hydroxide
higher temperature rise with stronger acid
77
define a homologous group
compounds of the same family with the general formula
78
percentage error
Va-Ve/Ve ABSOLUTE
79
