Which row correctly describes oxidation and reduction in terms of the transfer of electrons and changes in oxidation state?
| Transfer of electrons | Change in oxidation state | ||
| oxidation | reduction | oxidation | reduction |
A | gain | loss | increase | decrease |
B | loss | gain | increase | decrease |
C | loss | gain | decrease | increase |
D | gain | loss | decrease | increase |
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Which row describes the most common oxidation numbers of fluorine, oxygen and hydrogen in compounds?
| F | O | H |
A | +7 | -1 | -1 |
B | +1 | +2 | +1 |
C | -7 | -1 | -1 |
D | -1 | -2 | +1 |
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Below is a diagram of a voltaic cell. When the cell is running, what is happening in the salt bridge?
K+ ions flow to the zinc half-cell and NO3− ions flow to the copper half-cell
K+ ions flow to the copper half-cell and NO3− ions flow to the zinc half-cell
K+ and NO3− ions flow to the copper half-cell
K+ and NO3− ions flow to the zinc half-cell
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Which is the correct equation to calculate electromotive force?
EӨcell = EӨreduction + EӨoxidation
EӨcell = EӨreduction – EӨoxidation
EӨcell = EӨhydrogen + EӨreduction
EӨcell = EӨoxidation – EӨreduction
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Use the data below to help you answer this question.
Half-equation | Eθ / V |
Co3+ (aq) + e– ⇌ Co2+ (aq) | +1.82 |
Cr3+ (aq) + e– ⇌ Cr2+ (aq) | –0.41 |
Fe3+ (aq) + e– ⇌ Fe2+ (aq) | +0.77 |
S2O82– (aq) + 2e– ⇌ 2SO42– (aq) | +2.01 |
Which is the most powerful oxidising agent from all the species in the table?
Co3+ (aq)
Cr3+ (aq)
Fe3+ (aq)
SO42– (aq)
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Which reaction shows hydrogen behaving as an oxidising agent?
H2 + CuO → Cu + H2O
2Na + H2 → 2NaH
H2 + Cl2 → 2HCl
C2H4 + H2 → C2H6
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1 mark1.50 g of impure iron wire was dissolved in 30 cm3 of sulfuric acid. The resulting iron(II) sulfate solution was made up to 250 cm3 with distilled water. 25.0 cm3 of the resulting solution was acidified and titrated with 0.020 mol dm-3 potassium manganate(VII) solution.
20.0 cm3 of potassium manganate(VII) solution was required to reach the end-point of the titration.
5Fe2+ (aq) + MnO4– (aq) + 8H+ (aq) → 5Fe3+ (aq) + Mn2+ (aq) + 4H2O (l)
What is the percentage purity of the iron wire?
7.44
14.9
74.4
85.1
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1 markA cell is constructed from the two redox systems below.
Cu2+ (aq) + 2e– ⇌ Cu (s) Eθ = +0.34 V
Fe2+ (aq) + 2e– ⇌ Fe (s) Eθ = -0.77 V
Which statement(s) is / are correct for the cell?
The cell potential is 1.11 V
The reaction at the iron electrode is Fe (s) → Fe2+ (aq) + 2e–
The copper electrode increases in mass
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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The redox equilibria for a hydrogen-oxygen fuel cell in acidic conditions are shown below.
2H+ (aq) + 2e– ⇌ H2 (g) Eθ = 0.00 V
½O2 (g) + 2H+ (aq) + 2e– ⇌ H2O (l) Eθ = +1.23 V
What is the equation for the overall cell reaction?
½O2 (g) + 4H+ (aq) + 4e– → H2 (g) + H2O (l)
H2 (g) + H2O (l) → ½O2 (g) + 4H+ (aq) + 4e–
H2O (l) → H2 (g) + ½O2 (g)
H2 (g) + ½O2 (g) → H2O (l)
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1 markA cell is constructed from the two redox systems below.
Sn2+ (aq) + 2e– ⇌ Sn (s) Eθ = -0.14 V
Fe3+ (aq) + e– ⇌ Fe2+ (aq) Eθ = +0.77 V
What is the value of the electromotive force, in V?
-0.91
+0.63
+1.68
+0.91
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Which descriptions about the different systems used in batteries / cells are correct?
| Lead-acid | Nickel-cadmium | Hydrogen-oxygen |
A | Fuel | Rechargeable | Fuel |
B | Rechargeable | Fuel | Rechargeable |
C | Fuel | Fuel | Rechargeable |
D | Rechargeable | Rechargeable | Fuel |
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The overall equation for iodine-thiosulfate titrations is shown below.
2S2O32- (aq) + I2 (aq) → 2I– (aq) + S4O62- (aq)
Which statement(s) is / are correct for iodine-thiosulfate titrations?
Starch is added as an indicator at the start of the titration
The thiosulfate ion acts as a reducing agent
Iodine-thiosulfate titrations can be used to determine the copper content in alloys
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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If a dilute acid is added to an aqueous solution containing nitrate ions, NO2-, two different nitrogen compounds are released as gases.
2H+ (aq) + 2NO2- (aq) format('truetype')%3Bfont-weight%3Anormal%3Bfont-style%3Anormal%3B%7D%3C%2Fstyle%3E%3C%2Fdefs%3E%3Ctext%20font-family%3D%22math12bba9f4124283edd644799e0ce%22%20font-size%3D%2216%22%20text-anchor%3D%22middle%22%20x%3D%2210.5%22%20y%3D%2216%22%3E%26%23x2192%3B%3C%2Ftext%3E%3C%2Fsvg%3E){kind=small}
H2O (l) + NO (g) + NO2 (g)
Which of the three statements below correctly describe(s) the process?
1. The H+ (aq) ion is oxidised by NO2- (aq)
2. Some nitrogen atoms are oxidised, and some nitrogen atoms are reduced
3. The H+ (aq) ion acts as a catalyst
1 and 2 only
2 only
2 and 3 only
1, 2 and 3
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A voltaic cell consisting of zinc and silver is set up. The following overall reaction takes place:
Zn (s) + 2Ag+ (aq) → Zn2+ (aq) + 2Ag(s)
What are the correct half-equations at each electrode?
| Anode (negative electrode) | Cathode ( positive electrode) |
A | Ag (s) → Ag+ (aq) + e- | Zn2+ (aq) + 2e- → Zn (s) |
B | Ag+ (aq) + e- → Ag (s) | Zn (s) → Zn2+ (aq) + 2e- |
C | Zn (s) → Zn2+ (aq) + 2e- | Ag+ (aq) + e- → Ag (s) |
D | Zn2+ (aq) + 2e- → Zn (s) | Ag (s) → Ag+ (aq) + e- |
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Below are four descriptions about the movements of electrons in voltaic cells.
Which is the correct statement?
Electrons flow through the external wire from the cathode (positive electrode) to the anode (negative electrode)
Electrons flow through the external wire from the anode (negative electrode) to the cathode (positive electrode)
Electrons flow through the salt bridge from the oxidizing agent to the reducing agent
Electrons flow through the salt bridge from the reducing agent to the oxidizing agent
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Some standard electrode potential data is shown in the table.
Electrode half-equation | EӨ / V |
Co3+ (aq) + e– → Co2+ (aq) | +1.82 |
Cu2+ (aq) + 2e- ⇋ Cu (s) | +0.34 |
Fe3+ (aq) + e– → Fe2+ (aq) | +0.77 |
I2 (s) + 2e– → 2I– (aq) | +0.54 |
S2O82– (aq) + 2e– → 2SO42– (aq) | +2.01 |
Which species cannot catalyse the reaction between iodide ions, I– (aq), and peroxodisulfate ions, S2O82– (aq)?
Co2+
Cu2+
Fe2+
Fe3+
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What happens to the hydrogen in a hydrogen-oxygen fuel cell?
It is oxidised at the cathode
It is reduced at the cathode
It is oxidised at the anode
It is reduced at the anode
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