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AH Chemistry > what i got wrong in the past papers > Flashcards

what i got wrong in the past papers Flashcards

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1
Q

which reagent is most suitable for the gravimetric determination of magnesium ions in water?

A

sodium carbonate

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2
Q

are Fe3+ more stable than Fe2+ ions

A

yes

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3
Q

what is the oxidation state of Cr2O7 ions

A

+6

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4
Q

what is the oxidation state of MnO4 ions

A

+7

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5
Q

what is the oxidation state of VO2+ ions

A

+4

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6
Q

what is the oxidation state of Sn4+

A

+4

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7
Q

what are the units for a second order reaction

A

l mol-1 s-1

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8
Q

what are the units for a first order reaction

A

s-1

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9
Q

what are the units for a zero order reaction

A

mol l-1 s-1

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10
Q

what are the units for a third order reaction

A

mol -2 l2 s-1

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11
Q

what does it mean if n=2 (principle quantum number)

A

electron is in shell 2

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12
Q

what does it mean if l = 1

A

electron is in the p subshell

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13
Q

what does it mean if ml = -1

A

electron is in the orbital of -1

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14
Q

how can you work out the order of a reaction from the rate determining step

A

look at the number of moles of each of the reactants involved. 1 mole = first order etc

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15
Q

why may you dilute a sample for the colorimeter

A

becase the absorbance levels must not be outwith the calibration range

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16
Q

how can you find out the pKa values

A

the data booklet!

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17
Q

what is a cause for electrons becoming excited

A

heat/high temperatures

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18
Q

electron transitions involving the d-subshell can give rise to colour in transition metal complexes. why does a solution of an ion colourless

A

no d-d transitions are possible, so it does not absorb visible light

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19
Q

why may you use E=hf and not E=hlf

A

if the units in the question are J and not J mol or KJ mol

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20
Q

why may an experimentally determined value differ from the actual value, other than issues with the apparatus or transfer errors

A

impurities present in the substances

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21
Q

explain how the line of red light is produced

A
  • an electron is excited and promoted to a higher energy level
  • when it falls back down to a state, energy corresponding to the red light is emitted
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22
Q

why is recrystallisation necessary

A

to purify

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23
Q

describe how a mixed melting point experiment would be carried out and the result used to confirm the product was pure

A

sample mixed with pure substance
melting point of the mixture will be the same as the pure if the sample is pure

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24
Q

suggest an analytical technique which could be used to indicate whether the final sample is pure

A

thin layer chromatography

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25
Q

state the value of the m orbital which contains the tenth electron

A

-1 0 1

26
Q

explain how unpaired electrons can arise in a complex ion

A

less energy is required to promote an electron. electrons can be promoted between energy levels

27
Q

suggest an analytical techniwue that could be used to determine the presence of copper in spiders blood

A

atomic absorption

28
Q

state the oxidation number of vanadium in VO2

A

4

29
Q

explain why a substance may be described as a homogenous catalyst

A

same state as the ions in the reaction

30
Q

describe fully the procedure required to obtain results that would allow a calibration graph to be drawn

A

standard solutions prepared
suitable wavelength filter used
use of a blank
absorbance of each solution measured and noted

31
Q

the quantum number which specifies the shape of the orbital is the

A

angular momentum

32
Q

why may a spectrum have multiple lines

A

many different electron transitions in the visible region

33
Q

what piece of apparatus may be used to separate two immiscible layers

A

separating funnel

34
Q

state one way in which the identity of the product could be confirmed

A

mixed melting point analyis

35
Q

suggest how a student might test that no silver is remaining in the solution

A

add aldehyde to show a silver mirror

36
Q

how would an acidic buffer resist change in pH if a few more drops of the potassium hydroxide solution were added

A

the hydroxide ions would remove hydrogen ions from the solution
these hydrogen ions would be replaced by the dissociation of ethanoic acid molecules into ethanoate and hydrogen ions

37
Q

21 Which of the following would not be suitable
as a buffer solution?
A Boric acid and sodium borate
B Nitric acid and sodium nitrate
C Benzoic acid and sodium benzoate
D Propanoic acid and sodium propanoate

A

B

38
Q
  1. Which of the following salts will form a
    solution with the lowest pH?
    A Potassium chloride
    B Potassium ethanoate
    C Ammonium chloride
    D Ammonium ethanoate
A

C

39
Q
  1. Which of the following solids would form a
    colourless aqueous solution?
    A ZnSO4.7H2O
    B NiSO4.6H2O
    C K2CrO4
    D CoCl2
A

A

40
Q

8 What is the co-ordination number of the
transition metal in [Co(NH3)4(H2O)2]Cl3?
A 3
B 4
C 6
D 9

A

C

41
Q

what is meant by the term degenerate

A

contains the same energy

42
Q

explain whether visible light would provide sufficient energy to ionise gaseous sodium atoms

A

no because the wavelength required is too short

43
Q

what is a back titration

A

substance is not titrated itself but insteaed a compound is reacted with the substance and then the remaining compound is titrated to see how much did not react

44
Q

suggest a good control experiment that could be used for a back titration

A

repeat with a known volume of reactant rather than an excess

45
Q

what structural feature of indigo dye allows it to absorb light within the visible region of the electromagnetic spectrum

A

alternating double and single bonds

46
Q

why does a dye like indigo appear blue when viewed in daylight

A

red and green absorbed, blue transmitted

47
Q

how could filtration be sped up

A

vacuum filtration

48
Q

when is the use of an indicator in a titration not required

A

when the reactants are methanoic acid solution and ammonia solution

49
Q
  1. Which of the following statements about benzene is not true?
    A It is planar.
    B It is susceptible to attack by electrophilic reagents.
    C Its carbon to carbon bonds are equal in length.
    D It is readily attacked by bromine
A

D

50
Q

what does vacuum filtration use

A

buchner, hirsch or sintered glass funnel

51
Q

what does heating under reflux use

A

heating mantle water bath or bunsen burner

52
Q

what does distillation alloq

A

separation of liquids with similar boiling points

53
Q

how does distillation asses purity

A

by looking at the point at which a substance is separated by distillation

54
Q

Outline the steps for producing a calibration curve in colourimetr

A

A range of samples are prepared of known concentrationColorimeter readings are taken with the wavelength that is most appropriate (i.e. has the greatest absorbance –look for the opposing colour on the colour wheel from what you see)Dilutions to get samples are generally linear, but can be serial to give range. Burette and pipette are used for accuracy

55
Q

what is the criteria for solvent extraction

A

he solvent used must be immisciblewith the liquid mixture or solution (usually water) The solvent must also be one which the solute is moresoluble in than the liquid mixture or solution, volatileto allow the solute to be obtained by evaporation of the solvent and unreactivewith the solute.Extracting with multiplesmall volumes of solvent will extract a greater volume of solute than singleextraction.

56
Q

what is the purpose of recrystallisation

A

to purify an impure solid

57
Q

what are the steps involved in recrystallisation

A

dissolving an impure solid gently in a minimum volume of a hot solvent *hot filtration of the resulting mixture to remove any insoluble impurities *cooling the filtrate slowly to allow crystals of the pure compound to form, leaving soluble impurities dissolved in the solvent *filtering, washing and drying the pure crystals

58
Q

if the partition coefficient is high, which layer is the solute most soluble in

A

upper solvent

59
Q

Explain with 1moll-1of a strong acid has a lower pH than 1moll-1of a weak acid.

A

Since all of the ions dissociate in the strong acid there is a higher concentration of H+= lower pH

60
Q

what is an indicator

A

A substance with a clear colour change caused by distinct colours on each side of an equilbrium

61
Q

what is the colour of an indicator determined by

A

ratio of [HIn] to [In-

AH Chemistry (35 decks)

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