Pastpaper Questions Flashcards
1
Q
How can you reduce the poisoning of a catalyst, which is used in an industrial process
A
Purify reactants
2
Q
Why is the electrode potential for the standard hydrogen electrode is equal to 0V?
A
By definition
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
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’
5
Q
Why is the electron affinity of chlorine exothermic?
A
Net attraction between the chlorine nucleus and the extra electron
6
Q
Why would the entropy of a substance be 0 at 0K?
A
There is no disorder
7
Q
Would the entropy change between the liquid and gas be very large?
A
Big increase in entropy
8
Q
What happens to a reaction if the Gibbs free energy change is below 0?
A
It will be feasible and therefore spontaneous
9
Q
Write the formula for cisplatin
A
[PtCl2(NH3)2]
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
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
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+)
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
14
Q
What causes ionic bonding in relation to electronegativity?
A
A great enough difference between the electronegativities of the two elements
15
Q
Give the formula for phosphorus oxide(V)
A
P4O10
16
Q
Give the formula for a deep blue solution formed in an excess of conc NH3
A
[Cu(NH3)4(H2O)2]2+
17
Q
Give the formula for a green solution formed in an excess of aqueous NaOH
A
[Cr(OH)6]3-
18
Q
Give the formula for a yellow-green solution formed in an excess of conc HCl
A
[CuCl4]2-
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)
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
21
Q
Why does poisoning reduce the effectiveness of a heterogenous catalyst?
A
Attaches to the surface
22
Q
Give the meaning of the term ‘dynamic equilibrium’
A
- forward rate = backward rate
- concentration of reactants and products remain equal
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
24
Q
Name a benzene with two COOH groups attached to adjacent carbons
A
benzene-1,2-dicarboxylic acid
25
How would explain that a step is the rate-determining step?
The components of the rate equation appear in the correct ratio
26
Name a reactant and the observations made to distinguish an ester and a carboxylic acid
- Na2CO3
- no reaction with ester
- effervescence with carboxylic acid
27
Name a reactant and the observations made to distinguish a ketone and an acyl chloride
- AgNO3
- no reaction with ketone
- white precipitate with acyl chloride
28
What is the hydration for benzene?
152kJmol^(-1)
29
Define the enthalpy of lattice formation for calcium fluoride
The enthalpy change when 1 mole of CaF2 is formed from it's gaseous ions
30
Explain the interactions between water molecules and fluoride ions when the fluoride ions become hydrated
- water is polar
| - F(-) attracts water
31
Write an equation, with state symbols, for the process that occurs when potassium nitrate dissolves in water
KNO3(s) -> K+(aq) + NO3(-)(aq)
32
Why would an enthalpy of formation be different to a mean bond enthalpy?
- mean bond enthalpies are from a range of compounds
33
State the observations when sulfur burns in oxygen
- blue flame
| - smelly gas
34
Explain why Na2O reacts to form an alkaline solution when added to water
- O(2-) reacts with water
| - OH- forms
35
Suggest one reason why a thin layer of aluminium oxide protects aluminium from corrosion in moist air
Insoluble in water
36
Write an ionic equation to show aluminium oxide reacts with HCl
Al2O3 + 6H+ -> 2Al(3+) + 3H2O
37
Write an ionic equation to show how aluminium oxide reacts with aqueous sodium hydroxide
Al2O3 + 2OH- + 3H2O -> 2[Al(OH)4]-
38
Explain using an equation, why iron(III) ion are more acidic than iron(II) in aqueous solution
[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
39
Silicon(IV) oxide is insoluble in water
| Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide
SiO2 + 2NaOH -> Na2SiO3 + H2O
| - reacts with alkali
40
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
- Cr(OH)3 + 3H2O + 3H+ -> [Cr(H2O)6]3+
| - green solid to purple solution
41
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
Cr(OH)3 + 2H2O + OH- -> [Cr(H2O)2(OH)4]-
| From a green solid to a green solution
42
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
[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+ + 4H2O
| pale blue solution -> deep blue solution
43
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
[Co(H2O)6]2+ + 6NH3 -> [Co(NH3)6]2+ + 6H2O
| - pink solution -> straw solution
44
Write a reaction between [Fe(H2O)6]2+ ions and aqueous ammonia
Describe any observations
[Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+
| Green precipitate formed
45
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
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+)
46
Define bond dissociation enthalpy as applied to chlorine
- the enthalpy change to break the bond in 1 mol of chlorine
| - to form gaseous chlorine atoms
47
Explain why the lattice dissociation enthalpy of magnesium oxide is greater than that of magnesium chloride
- O(2-) has a greater charge
| - so attracts the Mg ion more strongly
48
What is one important mark to remember in bond calculations?
- using an algebraic equation first
49
Explain, in terms of structure and bonding, why sodium oxide has a high melting point
- sodium oxide is a giant ionic lattice
| - strong forces of attraction between ions
50
P3 oxides have basic properties, name the type of bond that causes this, and why it causes basic properties
- ionic
- contains O(2-) ions
- O(2-) ions accept protons to form OH-
51
Write an equation to show how sulfur dioxide reacts with water to form a weakly acidic solution
SO2 + H2O -> H+ + HSO3(-)
52
Why would sulfur dioxide form a weakly acidic solution?
- reaction is in equilibrium, SO2 partially dissociates
53
Suggest why SiO2 is described as an acidic oxide even though it is insoluble in water
SiO2 reacts with bases
54
Write an equation that would cause a colour change from yellow to orange, CrO4(2-) reacts with an excess of dilute sulfuric acid
2CrO4(2-) + 2H+ -> Cr2O7(2-) + H2O
55
How many NH3 molecules can bond to Cu(2+)?
4
56
Give the meaning of the term heterogenous
In a different state from reactants
57
Give one reason why impurities in the reactants can cause problems processes that use heterogeneous catalysts
Impurities poison the catalyst
58
Write two equations to show how Mn2+ is involved in the oxidation of C2O4(2-), with MnO4(-)
4Mn(2+) + MnO4(-) + 8H+ -> 5Mn(3+) + 4H2O
| 2Mn(3+) + C2O4(2-) -> 2Mn(2+) + 2CO2
59
When talking about cells what should you refer to?
E cell differences
60
Explain the meaning of the terms "ligand" and "bidentate" as applied to transition metal complexes
- ligand is an electron pair donor
| - bidentate ligand donates two electron pairs to a transition metal ion from different atoms
61
Give the angle of a Co-Cl bond in CoCl4(2-)
109.5
62
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
- 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
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
Forms a protective layer of MgO
64
Use your knowledge of bonding and explain why the melting of ice is an endothermic process
- H bonds bonds between water molecules
| - energy must be supplied in order to break them
65
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
Heat given out escapes to surroundings
66
In terms of structure and bonding, explain why SO2 has a low melting point
- it has a molecular structure
| - only has van der Waal forced in between molecules which is a weak force
67
Explain why the melting point of P4O10 is higher than the melting point of SO2
- P4O10 has bigger molecules
| - therefore more electrons, and stronger van der Waal forces in between molecules
68
Write an equation for the acid-base reaction that occurs when Na2O reacts with P4O10, without water
6Na2O + P4O10 -> 4Na3PO4
69
What is the solution in a hydrogen standard electrode
HCl
70
What is the salt bridge made out of in a standard hydrogen electrode?
KCl
71
Suggest one reason why the redox reaction between chlorine and water does not normally occur in the absence of light
Activation energy is high, light provides that energy to break Cl-Cl bond
72
Write an equation for the reaction between manganate ions and ethanedioate ions in acidic solution
2MnO4- + 16H+ + 5C2O4(2-) -> 2Mn(2+) + 8H2O + 10CO2
73
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-))
- MnO4- ions are coloured purple
| - all other reactants and products are not coloured
74
Write two equations to show how the catalyst Mn2+ is involved in the reaction between MnO4- and C2O4(2-)
4Mn(2+) + MnO4(-) + 8H+ -> 5Mn(3+) + 4H2O
| 2Mn(3+) + C2O4(2-) -> 2Mn(2+) + 2CO2
75
Define the term Lewis base
Electron pair donor
76
Write an equation for the reaction between aqueous copper ions and ammonia, in which ammonia acts as a Brønsted-Lowry base. State any observations.
[Cu(H2O)6]2+ + 2NH3 -> Cu(H2O)4(OH)2 + 2NH4+
| Blue solution to blue precipitate
77
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
[Cu(H2O)6]2+ + 4NH3 -> [Cu(H2O)2(NH3)4]2+ + 4H2O
| Pale solution to deep blue solution
78
Name the two T.M that do not form any complex ions with NH3 in e.g M(NH3)4(H2O)2
- Fe(ll) ions
- Fe(lll) ions
- Al(lll) ions
79
Write an equation between Fe(ll) hexa aqua ions and excess dilute ammonia, state any changes
[Fe(H2O)6]2+ + 2NH3 -> [Fe(H2O)4(OH)2] + 2NH4+
| Green solution to a green ppt
80
Write an equation between aqueous Al ions and excess aqueous diaminoethane
State the appearance of the aluminium-containing product
2[Al(H2O)6]3+ + 3H2NCH2CH2NH2 -> 2Al(H2O)3(OH)3 + 3[H3NCH2CH2NH3]2+
White ppt
81
Write a reaction for the change of Co(II) to Co(III) in air, with en
4[Co(NH2CH2CH2NH2)3]2+ + O2 + 2H2O -> 4[Co(H2NCH2CH2NH2)]3+ + 4OH-
82
Electron affinity
The enthalpy change when 1 mol of gaseous atoms are converted to 1 mol of gaseous ions each with a single negative charge
83
Explain why the electronegativity of fluorine is greater than the electronegativity of chlorine
- F atom is smaller
| - electrons attracted more strongly to the nucleus
84
Explain why the hydration enthalpy of the fluoride ion is more negative than the hydration enthalpy of the chloride ion
- F- ions smaller
| - F- is strongly attracted to the delta positive on the hydrogen on water
85
Write an equation for the enthalpy of solution, using lattice dissociation and sum of hydration enthalpies
Enthalpy of solution = lattice dissociation + hydration enthalpies
86
State one environmental advantage of a rechargeable cell compared with the non-rechargeable cell
The cell can be re-used
87
Suggest why ethanol can be considered to be a carbon-neutral fuel
- CO2 released by combustion
| - CO2 taken up in photosynthesis
88
State the 3 colours associated the different oxidation states of Cr
Cr2+ - blue
Cr3+ - green
Cr6+ - orange
89
Write a reaction potassium dichromate reacts with Zn
Cr2O7(2-) + 14H+ + 3Zn -> 2Cr(3+) +3Zn(2+) + 7H2O
90
Write a reaction for the reduction of Cr(3+) with Zn
2Cr(3+) + Zn -> 2Cr(2+) + Zn(2+)
91
What colour is [Cr(OH)6]3-
Green solution
92
What would you call this reaction [Cr(H2O)6]3+ -> [Cr(H2O)5Cl]2+
Ligand substitution
93
Suggest, in terms of electrons, why the colours of the complex ions are different
- energy gaps for d electrons are different for each complex
| - so a different wavelength is absorbed
94
Explain why [Cr(H2O)6]3+ ions behave differently to [Cr(H2O)6]2+ ions
- Cr(lll) behaves differently because it is acidic
| - Cr3+ ion polarises water
95
[Co(H2O)6]2+ -> blue solution
Write an equation for this
Name a reagent
[Co(H2O)6]2+ + 4Cl- -> [CoCl4]2- + 6H2O
| HCl
96
Lattice dissociation enthalpy
The enthalpy change when a solid ionic compound separates into it's gaseous ions
97
Explain in terms of structure and bonding, why SiO2 has a high melting point
- macromolecular
| - strong covalent bonds between atoms
98
Why is the melting point of Li2O higher than Na2O?
- Li+ ion is smaller than Na+
| - attracts O(2-) more strongly
99
State the feature of transition metals is the cause of these properties:
- complex formation
- coloured ions
- catalytic activity
Incomplete d orbitals
100
Name the 4th characteristic property of transition metals
- complex formation
- coloured ions
- catalytic activity
Variable oxidation state
101
How can you maximise the efficiency of a heterogenous catalyst such as V2O5?
- increase SA
| - by using powder
102
Give the meaning of the term multidentate
Forms two or more co-ordinate bonds
103
If a complex ion contains CN- which is toxic, why is the overall complex ion not toxic?
- strongly bonded to the TM by co-ordinate bond
104
Suggest why water is not used a solvent with a cell containing Li and CoO2?
Li reacts with water
105
Give the formula of the complex ion formed, when excess dilute NH3 is added to [Cu(H2O)6]2+
[Cu(NH3)4(H2O)2]2+
106
Give the colour [Cr(OH)6]3-
Green
107
Write a reaction between [Cr(OH)6]3- and H2O2 to form CrO4-
2[Cr(OH)6]3- + 3H2O2 -> 2CrO4(2-) + 2OH- + 8H2O
108
Give the ratio of the moles of MnO4(-) to H2O2
2:5
109
Observations when Mg reacts with steam
- Bright light
| - white smoke
110
Give two physical properties for SiO2
- hard
| - brittle
111
Write a standard electrode potential of iron (Fe/Fe2+)
Pt|H2|H+||Fe2+|Fe
112
Why would something be a positive electrode
Higher E(theta) value
113
Deduce half equations for a hydrogen-oxygen fuel cell
2OH- + H2 -> 2H2O + 2e-
| 4e- + 2H2O + O2 -> 4OH-
114
Explain how a electric current can be generated in a fuel cell
- hydrogen electrode provides electrons
| - oxygen electrode accepts electrons
115
Give the main advantage of using a fuel cell over an internal combustion engine
- more efficient
116
How do you go from Cr2O7(2-) to Cr(3+)?
- H+/Zn
- Cr2O7(2-) + 14H+ + 6e- -> 2Cr(3+) + 7H2O
- Zn -> Zn(2+) + 2e-
117
Write an equation for going from CrO4(2-) to Cr2O7(2-) and state the colour change
2CrO4(2-) + 2H+ Cr2O7(2-) + H2O
118
Write the two half equations, for going from Cr(3+) to Cr(2+)
Cr(3+) + e- -> Cr(2+)
| Zn -> Zn(2+) + 2e-
119
Write an equation for the oxidation of [Cr(OH)6]3- by H2O2
2[Cr(OH)6]3- + 3H2O2 -> 2CrO4(2-) + 2OH- + 8H2O
120
State the feature of transition metals that gives the characteristics of T.Ms
- incomplete d orbitals
121
Name the 4 characteristic properties of transition metals
- complex formation
- coloured ions
- catalytic activity
- variable oxidation state
122
Give the meaning of the term multidentate
Forms two or more co-ordinate bonds
123
Suggest two properties of ions that influence the value of a lattice enthalpy(perfect ionic model)
- radius
| - charge
124
Suggest why silicon dioxide is insoluble in water
- water can't break the covalent bonds
125
Write a reaction between aluminium oxide and an excess of aqueous sodium hydroxide
Al2O3 + 2NaOH -> 2NaAl(OH)4
126
Explain why Fe(3+) ions are as effective as Fe(2+) ions in catalysing this reaction
(S2O8 and I2)
Reactions can happen in any order
127
Give two reasons why using scrap iron to extract copper is more environmentally friendly than roasting
- less CO2 released into atmosphere
| - lower energy consumption
