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Chemistry Unit 5 > Pastpaper Questions > Flashcards

Pastpaper Questions Flashcards

1
Q

How can you reduce the poisoning of a catalyst, which is used in an industrial process

A

Purify reactants

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2
Q

Why is the electrode potential for the standard hydrogen electrode is equal to 0V?

A

By definition

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3
Q

Give a main advantage of a fuel cell over a rechargeable cell (other than lack of pollution)

A

It has a continuous supply of H2 and O2

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4
Q

Why might a fuel cell not be ‘carbon neutral’ ?

A

Hydrogen may need to be made using an energy source that is not ‘carbon neutral’

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5
Q

Why is the electron affinity of chlorine exothermic?

A

Net attraction between the chlorine nucleus and the extra electron

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6
Q

Why would the entropy of a substance be 0 at 0K?

A

There is no disorder

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7
Q

Would the entropy change between the liquid and gas be very large?

A

Big increase in entropy

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8
Q

What happens to a reaction if the Gibbs free energy change is below 0?

A

It will be feasible and therefore spontaneous

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9
Q

Write the formula for cisplatin

A

[PtCl2(NH3)2]

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10
Q

State and explain one risk with the use of cisplatin as an anti cancer drug

A
  • tumours

- attached to DNA in normal cells

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11
Q

Why would a complex ion with H2NCH2CH2NH2 as a ligand be more stable than a hexa-aqua ion?

A
  • entropy change is positive

- 4 moles of reactants form 7 moles of products

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12
Q

Why is the co-ordination number different in CoCl2 to [CoCl4]2- ?

A

Cl- ligand is too big to fit more than 4 round Co(2+)

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13
Q

State and explain the trend in lector negativities across Period 3 from sodium to sulfur

A
  • increases
  • proton no. increases (nuclear charge)
  • same number of electron shells
  • attraction of bond pair to nucleus increases
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14
Q

What causes ionic bonding in relation to electronegativity?

A

A great enough difference between the electronegativities of the two elements

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15
Q

Give the formula for phosphorus oxide(V)

A

P4O10

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16
Q

Give the formula for a deep blue solution formed in an excess of conc NH3

A

[Cu(NH3)4(H2O)2]2+

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17
Q

Give the formula for a green solution formed in an excess of aqueous NaOH

A

[Cr(OH)6]3-

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18
Q

Give the formula for a yellow-green solution formed in an excess of conc HCl

A

[CuCl4]2-

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19
Q

Give two reasons why the use of a spectrometer is the most appropriate method for measuring the concentration of coloured ions

A
  • rapid determination of concentration

- does not use up any reagent(doesn’t interfere with reaction)

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20
Q

Draw and explain a graph for the conc of MnO4- against time

A
  • low initial gradient because negative ions collide so activation energy is high
  • becomes steeper due to production of Mn(2+) autocatalyst
  • curve levels out approaching time axis
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21
Q

Why does poisoning reduce the effectiveness of a heterogenous catalyst?

A

Attaches to the surface

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22
Q

Give the meaning of the term ‘dynamic equilibrium’

A
  • forward rate = backward rate

- concentration of reactants and products remain equal

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23
Q

What happens when an amino acid reacts with an excess of bromomethane

A

The H’s and lone pair on N become CH3

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24
Q

Name a benzene with two COOH groups attached to adjacent carbons

A

benzene-1,2-dicarboxylic acid

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25
Q

How would explain that a step is the rate-determining step?

A

The components of the rate equation appear in the correct ratio

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26
Q

Name a reactant and the observations made to distinguish an ester and a carboxylic acid

A
  • Na2CO3
  • no reaction with ester
  • effervescence with carboxylic acid
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27
Q

Name a reactant and the observations made to distinguish a ketone and an acyl chloride

A
  • AgNO3
  • no reaction with ketone
  • white precipitate with acyl chloride
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28
Q

What is the hydration for benzene?

A

152kJmol^(-1)

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29
Q

Define the enthalpy of lattice formation for calcium fluoride

A

The enthalpy change when 1 mole of CaF2 is formed from it’s gaseous ions

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30
Q

Explain the interactions between water molecules and fluoride ions when the fluoride ions become hydrated

A
  • water is polar

- F(-) attracts water

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31
Q

Write an equation, with state symbols, for the process that occurs when potassium nitrate dissolves in water

A

KNO3(s) -> K+(aq) + NO3(-)(aq)

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32
Q

Why would an enthalpy of formation be different to a mean bond enthalpy?

A
  • mean bond enthalpies are from a range of compounds
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33
Q

State the observations when sulfur burns in oxygen

A
  • blue flame

- smelly gas

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34
Q

Explain why Na2O reacts to form an alkaline solution when added to water

A
  • O(2-) reacts with water

- OH- forms

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35
Q

Suggest one reason why a thin layer of aluminium oxide protects aluminium from corrosion in moist air

A

Insoluble in water

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36
Q

Write an ionic equation to show aluminium oxide reacts with HCl

A

Al2O3 + 6H+ -> 2Al(3+) + 3H2O

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37
Q

Write an ionic equation to show how aluminium oxide reacts with aqueous sodium hydroxide

A

Al2O3 + 2OH- + 3H2O -> 2[Al(OH)4]-

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38
Q

Explain using an equation, why iron(III) ion are more acidic than iron(II) in aqueous solution

A

[Fe(H2O)6]3+ -> [Fe(H2O)5(OH)]2+
+ H+
- Fe(3+) has a higher charge to size than Fe(2+)
- increases polarisation of co-ordinated water

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39
Q

Silicon(IV) oxide is insoluble in water

Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide

A

SiO2 + 2NaOH -> Na2SiO3 + H2O

- reacts with alkali

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40
Q

Write an ionic equation for the reaction of chromium(III) hydroxide with dilute hydrochloric acid
Describe the changes that would be observed in this reaction

A
  • Cr(OH)3 + 3H2O + 3H+ -> [Cr(H2O)6]3+

- green solid to purple solution

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41
Q

Write an ionic equation for the reaction of chromium(III) hydroxide with dilute aqueous sodium hydroxide
Describe the changes that would be observed in this reaction

A

Cr(OH)3 + 2H2O + OH- -> [Cr(H2O)2(OH)4]-

From a green solid to a green solution

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42
Q

Write an equation for the reaction of aqueous copper(II) sulfate with excess dilute aqueous ammonia
Describe the changes that would be observed in this reaction

A

[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+ + 4H2O

pale blue solution -> deep blue solution

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43
Q

Write an equation for the reaction of cobalt(II) sulfate with excess dilute aqueous ammonia
Describe the changes that would be observed in this reaction

A

[Co(H2O)6]2+ + 6NH3 -> [Co(NH3)6]2+ + 6H2O

- pink solution -> straw solution

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44
Q

Write a reaction between [Fe(H2O)6]2+ ions and aqueous ammonia
Describe any observations

A

[Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+

Green precipitate formed

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45
Q

The redox reaction, in aqueous solution, between acidified potassium manganate(VII) and sodium ethanedioate is autocatalysed

  • write an equation for the redox
  • identify the species that acts as the catalyst
  • explain how the properties of the species enable it to act as a catalyst in this reaction
A

2MnO4(-) + 16H+ + 5C2O4(2-) -> 2Mn(2+) + 8H2O + 10CO2

  • catalyst is Mn(2+)
  • possible because Mn can exist in variable oxidation states
  • Ea is lowered because oppositely charged ions attract
  • Mn(3+) + C2O4(2-) -> Mn(2+)
  • Mn(2+) + MnO4(-) -> Mn(3+)
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46
Q

Define bond dissociation enthalpy as applied to chlorine

A
  • the enthalpy change to break the bond in 1 mol of chlorine

- to form gaseous chlorine atoms

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47
Q

Explain why the lattice dissociation enthalpy of magnesium oxide is greater than that of magnesium chloride

A
  • O(2-) has a greater charge

- so attracts the Mg ion more strongly

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48
Q

What is one important mark to remember in bond calculations?

A
  • using an algebraic equation first
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49
Q

Explain, in terms of structure and bonding, why sodium oxide has a high melting point

A
  • sodium oxide is a giant ionic lattice

- strong forces of attraction between ions

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50
Q

P3 oxides have basic properties, name the type of bond that causes this, and why it causes basic properties

A
  • ionic
  • contains O(2-) ions
  • O(2-) ions accept protons to form OH-
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51
Q

Write an equation to show how sulfur dioxide reacts with water to form a weakly acidic solution

A

SO2 + H2O -> H+ + HSO3(-)

52
Q

Why would sulfur dioxide form a weakly acidic solution?

A
  • reaction is in equilibrium, SO2 partially dissociates
53
Q

Suggest why SiO2 is described as an acidic oxide even though it is insoluble in water

A

SiO2 reacts with bases

54
Q

Write an equation that would cause a colour change from yellow to orange, CrO4(2-) reacts with an excess of dilute sulfuric acid

A

2CrO4(2-) + 2H+ -> Cr2O7(2-) + H2O

55
Q

How many NH3 molecules can bond to Cu(2+)?

A

4

56
Q

Give the meaning of the term heterogenous

A

In a different state from reactants

57
Q

Give one reason why impurities in the reactants can cause problems processes that use heterogeneous catalysts

A

Impurities poison the catalyst

58
Q

Write two equations to show how Mn2+ is involved in the oxidation of C2O4(2-), with MnO4(-)

A

4Mn(2+) + MnO4(-) + 8H+ -> 5Mn(3+) + 4H2O

2Mn(3+) + C2O4(2-) -> 2Mn(2+) + 2CO2

59
Q

When talking about cells what should you refer to?

A

E cell differences

60
Q

Explain the meaning of the terms “ligand” and “bidentate” as applied to transition metal complexes

A
  • ligand is an electron pair donor

- bidentate ligand donates two electron pairs to a transition metal ion from different atoms

61
Q

Give the angle of a Co-Cl bond in CoCl4(2-)

A

109.5

62
Q

The complex ion formed in aqueous solution between Co(2+) ions and Cl- ions is a different colour from the [Co(H2O)6]2+ ion.
Explain why these complex ions have different colours

A
  • in different complexes the d orbitals of cobalt will have different energies
  • light is absorbed causing an expectation to be excited
  • different wavelength of light absorbed
63
Q

Suggest one reason why a sample of Mg stays stable in air at room temp, despite the a negative value for G, for the formation of MgO

A

Forms a protective layer of MgO

64
Q

Use your knowledge of bonding and explain why the melting of ice is an endothermic process

A
  • H bonds bonds between water molecules

- energy must be supplied in order to break them

65
Q

The freezing of water is an exothermic process, give one reason why the temp of a sample of water can stay at a constant value of 0 when freezing

A

Heat given out escapes to surroundings

66
Q

In terms of structure and bonding, explain why SO2 has a low melting point

A
  • it has a molecular structure

- only has van der Waal forced in between molecules which is a weak force

67
Q

Explain why the melting point of P4O10 is higher than the melting point of SO2

A
  • P4O10 has bigger molecules

- therefore more electrons, and stronger van der Waal forces in between molecules

68
Q

Write an equation for the acid-base reaction that occurs when Na2O reacts with P4O10, without water

A

6Na2O + P4O10 -> 4Na3PO4

69
Q

What is the solution in a hydrogen standard electrode

A

HCl

70
Q

What is the salt bridge made out of in a standard hydrogen electrode?

A

KCl

71
Q

Suggest one reason why the redox reaction between chlorine and water does not normally occur in the absence of light

A

Activation energy is high, light provides that energy to break Cl-Cl bond

72
Q

Write an equation for the reaction between manganate ions and ethanedioate ions in acidic solution

A

2MnO4- + 16H+ + 5C2O4(2-) -> 2Mn(2+) + 8H2O + 10CO2

73
Q

By considering the properties of reactants and products, state why it is possible to use a spectrometer to measure the concentration of the manganate ions in this reaction mixture
(C2O4(2-))

A
  • MnO4- ions are coloured purple

- all other reactants and products are not coloured

74
Q

Write two equations to show how the catalyst Mn2+ is involved in the reaction between MnO4- and C2O4(2-)

A

4Mn(2+) + MnO4(-) + 8H+ -> 5Mn(3+) + 4H2O

2Mn(3+) + C2O4(2-) -> 2Mn(2+) + 2CO2

75
Q

Define the term Lewis base

A

Electron pair donor

76
Q

Write an equation for the reaction between aqueous copper ions and ammonia, in which ammonia acts as a Brønsted-Lowry base. State any observations.

A

[Cu(H2O)6]2+ + 2NH3 -> Cu(H2O)4(OH)2 + 2NH4+

Blue solution to blue precipitate

77
Q

Write an equation for a reaction between ammonia and aqueous copper ions, in which ammonia acts as a Lewis base but not BL base
State any observations

A

[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+ + 4H2O

Pale solution to deep blue solution

78
Q

Name the two T.M that do not form any complex ions with NH3 in e.g M(NH3)4(H2O)2

A
  • Fe(ll) ions
  • Fe(lll) ions
  • Al(lll) ions
79
Q

Write an equation between Fe(ll) hexa aqua ions and excess dilute ammonia, state any changes

A

[Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+

Green solution to a green ppt

80
Q

Write an equation between aqueous Al ions and excess aqueous diaminoethane
State the appearance of the aluminium-containing product

A

2[Al(H2O)6]3+ + 3H2NCH2CH2NH2 -> 2Al(H2O)3(OH)3 + 3[H3NCH2CH2NH3]2+
White ppt

81
Q

Write a reaction for the change of Co(II) to Co(III) in air, with en

A

4[Co(NH2CH2CH2NH2)3]2+ + O2 + 2H2O -> 4[Co(H2NCH2CH2NH2)]3+ + 4OH-

82
Q

Electron affinity

A

The enthalpy change when 1 mol of gaseous atoms are converted to 1 mol of gaseous ions each with a single negative charge

83
Q

Explain why the electronegativity of fluorine is greater than the electronegativity of chlorine

A
  • F atom is smaller

- electrons attracted more strongly to the nucleus

84
Q

Explain why the hydration enthalpy of the fluoride ion is more negative than the hydration enthalpy of the chloride ion

A
  • F- ions smaller

- F- is strongly attracted to the delta positive on the hydrogen on water

85
Q

Write an equation for the enthalpy of solution, using lattice dissociation and sum of hydration enthalpies

A

Enthalpy of solution = lattice dissociation + hydration enthalpies

86
Q

State one environmental advantage of a rechargeable cell compared with the non-rechargeable cell

A

The cell can be re-used

87
Q

Suggest why ethanol can be considered to be a carbon-neutral fuel

A
  • CO2 released by combustion

- CO2 taken up in photosynthesis

88
Q

State the 3 colours associated the different oxidation states of Cr

A

Cr2+ - blue
Cr3+ - green
Cr6+ - orange

89
Q

Write a reaction potassium dichromate reacts with Zn

A

Cr2O7(2-) + 14H+ + 3Zn -> 2Cr(3+) +3Zn(2+) + 7H2O

90
Q

Write a reaction for the reduction of Cr(3+) with Zn

A

2Cr(3+) + Zn -> 2Cr(2+) + Zn(2+)

91
Q

What colour is [Cr(OH)6]3-

A

Green solution

92
Q

What would you call this reaction [Cr(H2O)6]3+ -> [Cr(H2O)5Cl]2+

A

Ligand substitution

93
Q

Suggest, in terms of electrons, why the colours of the complex ions are different

A
  • energy gaps for d electrons are different for each complex

- so a different wavelength is absorbed

94
Q

Explain why [Cr(H2O)6]3+ ions behave differently to [Cr(H2O)6]2+ ions

A
  • Cr(lll) behaves differently because it is acidic

- Cr3+ ion polarises water

95
Q

[Co(H2O)6]2+ -> blue solution
Write an equation for this
Name a reagent

A

[Co(H2O)6]2+ + 4Cl- -> [CoCl4]2- + 6H2O

HCl

96
Q

Lattice dissociation enthalpy

A

The enthalpy change when a solid ionic compound separates into it’s gaseous ions

97
Q

Explain in terms of structure and bonding, why SiO2 has a high melting point

A
  • macromolecular

- strong covalent bonds between atoms

98
Q

Why is the melting point of Li2O higher than Na2O?

A
  • Li+ ion is smaller than Na+

- attracts O(2-) more strongly

99
Q

State the feature of transition metals is the cause of these properties:

  • complex formation
  • coloured ions
  • catalytic activity
A

Incomplete d orbitals

100
Q

Name the 4th characteristic property of transition metals

  • complex formation
  • coloured ions
  • catalytic activity
A

Variable oxidation state

101
Q

How can you maximise the efficiency of a heterogenous catalyst such as V2O5?

A
  • increase SA

- by using powder

102
Q

Give the meaning of the term multidentate

A

Forms two or more co-ordinate bonds

103
Q

If a complex ion contains CN- which is toxic, why is the overall complex ion not toxic?

A
  • strongly bonded to the TM by co-ordinate bond
104
Q

Suggest why water is not used a solvent with a cell containing Li and CoO2?

A

Li reacts with water

105
Q

Give the formula of the complex ion formed, when excess dilute NH3 is added to [Cu(H2O)6]2+

A

[Cu(NH3)4(H2O)2]2+

106
Q

Give the colour [Cr(OH)6]3-

A

Green

107
Q

Write a reaction between [Cr(OH)6]3- and H2O2 to form CrO4-

A

2[Cr(OH)6]3- + 3H2O2 -> 2CrO4(2-) + 2OH- + 8H2O

108
Q

Give the ratio of the moles of MnO4(-) to H2O2

A

2:5

109
Q

Observations when Mg reacts with steam

A
  • Bright light

- white smoke

110
Q

Give two physical properties for SiO2

A
  • hard

- brittle

111
Q

Write a standard electrode potential of iron (Fe/Fe2+)

A

Pt|H2|H+||Fe2+|Fe

112
Q

Why would something be a positive electrode

A

Higher E(theta) value

113
Q

Deduce half equations for a hydrogen-oxygen fuel cell

A

2OH- + H2 -> 2H2O + 2e-

4e- + 2H2O + O2 -> 4OH-

114
Q

Explain how a electric current can be generated in a fuel cell

A
  • hydrogen electrode provides electrons

- oxygen electrode accepts electrons

115
Q

Give the main advantage of using a fuel cell over an internal combustion engine

A
  • more efficient
116
Q

How do you go from Cr2O7(2-) to Cr(3+)?

A
  • H+/Zn
  • Cr2O7(2-) + 14H+ + 6e- -> 2Cr(3+) + 7H2O
  • Zn -> Zn(2+) + 2e-
117
Q

Write an equation for going from CrO4(2-) to Cr2O7(2-) and state the colour change

A

2CrO4(2-) + 2H+ Cr2O7(2-) + H2O

118
Q

Write the two half equations, for going from Cr(3+) to Cr(2+)

A

Cr(3+) + e- -> Cr(2+)

Zn -> Zn(2+) + 2e-

119
Q

Write an equation for the oxidation of [Cr(OH)6]3- by H2O2

A

2[Cr(OH)6]3- + 3H2O2 -> 2CrO4(2-) + 2OH- + 8H2O

120
Q

State the feature of transition metals that gives the characteristics of T.Ms

A
  • incomplete d orbitals
121
Q

Name the 4 characteristic properties of transition metals

A
  • complex formation
  • coloured ions
  • catalytic activity
  • variable oxidation state
122
Q

Give the meaning of the term multidentate

A

Forms two or more co-ordinate bonds

123
Q

Suggest two properties of ions that influence the value of a lattice enthalpy(perfect ionic model)

A
  • radius

- charge

124
Q

Suggest why silicon dioxide is insoluble in water

A
  • water can’t break the covalent bonds
125
Q

Write a reaction between aluminium oxide and an excess of aqueous sodium hydroxide

A

Al2O3 + 2NaOH -> 2NaAl(OH)4

126
Q

Explain why Fe(3+) ions are as effective as Fe(2+) ions in catalysing this reaction
(S2O8 and I2)

A

Reactions can happen in any order

127
Q

Give two reasons why using scrap iron to extract copper is more environmentally friendly than roasting

A
  • less CO2 released into atmosphere

- lower energy consumption

Chemistry Unit 5 (2 decks)

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