Which row correctly describes oxidation in terms of oxygen, electrons and oxidation state?
| oxygen is | electrons are | oxidation state is | |
| A | added | added | increased |
| B | added | lost | increased |
| C | lost | added | decreased |
| D | lost | lost | decreased |
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Magnesium reacts with iron(III) oxide in the following reaction.
magnesium + iron(III) oxide → magnesium oxide + iron
Which statement about this reaction is correct?
Magnesium oxide is reduced
Iron is oxidised
Magnesium is oxidised
Iron(III) oxide is oxidised
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When copper is heated in air, its surface turns black.
What is happening to the copper in this reaction?
Copper undergoes thermal decomposition
Copper is oxidised
Copper burns with a lilac flame
Copper is reduced
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Lead(II) oxide undergoes a number of different redox reactions.
In which of the following reactions is lead(II) oxide, PbO, not reduced?
PbO + Zn → Pb + ZnO
PbO + H2 → Pb + H2O
PbO + C → Pb + CO
2PbO + O2 → 2PbO2
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The following equations are all examples of redox reactions.
In which equation is the underlined substance being oxidised?
CO2 + C → 2CO
FeO + Mg → MgO + Fe
3CO + Fe2O3 → 2Fe + 3CO2
CuCO3 → CuO + CO2
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A series of redox reactions are shown. What is the oxide that undergoes oxidation?
| 1 | 2CO + 2NO → 2CO2 + N2 |
| 2 | Fe2O3 + 2Al → Al2O3 + 2Fe |
| 3 | 2ZnO + C → 2Zn + CO2 |
| 4 | Fe2O3 + 3CO → 2Fe + 3CO2 |
CO
C
NO
Fe2O3
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In which reaction is the reactant being reduced?
Mg → Mg2+ + 2ē
Mg2+ + 2ē → Mg
CrO → Cr2O3
C → CO2
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Vanadium is a transition element and forms several oxides. In which of the following reactions does vanadium undergo oxidation?
V2O3 → VO
V2O5 → VO2
V2O3 → V2O5
VO2 → V2O3
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Manganese is a transition element and forms several oxides. In which of the following changes does manganese undergo reduction?
Mn2O3 → Mn2O7
MnO → MnO3
Mn2O2 → MnO
MnO → Mn
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Potassium manganate (VII) is used to test for the presence of reducing agents. Which row correctly describes what happens when acidified potassium manganate (VII) is added to a solution containing a reducing agent?
| colour change | reason for colour change | |
| A | pink/purple to colourless | MnO4- is oxidised |
| B | pink/purple to colourless | MnO4- is reduced |
| C | colourless to pink/purple | MnO4- is oxidised |
| D | colourless to pink/purple | MnO4- is reduced |
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Which row correctly describes an oxidising agent and a reducing agent?
| oxidising agent | reducing agent | |
| A | adds oxygen to a substance | removes oxygen from a substance |
| B | adds oxygen to a substance | increases the oxidation number of a substance |
| C | removes oxygen from a substance | adds oxygen to a substance |
| D | decreases the oxidation number of a substance | increases the oxidation number of a substance |
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Which one of the following substances is commonly used as a reducing agent?
H2SO4
KMnO4
H2O2
CO
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In which two of the following redox reactions is the substance in bold acting as a reducing agent?
| 1 | CuO + H2 → Cu + H2O |
| 2 | 2Ca + O2 → 2CaO |
| 3 | CO + CuO → Cu + CO2 |
| 4 | CO2 + C → 2CO |
1 and 2 only
1 and 3 only
2 and 3 only
All of them
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Hydrogen and copper(II) oxide react to produce copper metal and water.
CuO + H2 → Cu + H2O
Which row correctly describes the oxidising agent and reducing agent?
| oxidising agent | reducing agent | |
| A | H2O | Cu |
| B | H2 | CuO |
| C | Cu | H2O |
| D | CuO | H2 |
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Three reactions are shown below.
NO + O3 → NO2 + O2
2C + O2 → 2CO
2MgO + O2 → 2MgO2
Which row correctly describes the process each reactant molecule undergoes?
| NO | O3 | MgO | |
| A | oxidised | reduced | oxidised |
| B | oxidised | oxidised | reduced |
| C | reduced | oxidised | oxidised |
| D | reduced | reduced | oxidised |
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What is the oxidation state of Fe in Fe2O3?
+2
-2
-3
+3
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Which row correctly describes the process of reduction in terms of oxygen, electrons and oxidation state?
| oxygen is | electrons are | oxidation state is | |
| A | lost | added | unchanged |
| B | added | lost | increased |
| C | lost | added | decreased |
| D | added | lost | unchanged |
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Which row correctly names each compound?
| CuSO4 | KMnO4 | FeCl3 | |
| A | copper sulfate | potassium manganate (IV) | iron(II) chloride |
| B | copper sulfate | potassium manganate (V) | iron(III) chloride |
| C | copper(II) sulfate | potassium manganate (VI) | iron(II) chloride |
| D | copper(II) sulfate | potassium manganate (VII) | iron(III) chloride |
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Potassium iodide is used to test for the presence of oxidising agents. Which row correctly describes what happens when potassium iodide is added to an acidified solution containing an oxidising agent?
| colour change | reason for colour change | |
| A | turns brown | iodine is used up |
| B | turns brown | iodine is formed |
| C | turns yellow | iodine is used up |
| D | no colour change | iodine is formed |
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