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 B C D | Gain Loss Loss Gain | Loss Gain Loss Gain | Increase Increase Decrease Decrease | Decrease Decrease Increase Increase |
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The heptahydrate mineral of magnesium sulfate is used in Epsom Salts for preparing therapeutic baths. Magnesium sulfate is also used in some medical applications.
What is the oxidation state of MgSO4?
-2
+2
+7
0
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Which row describes the most common oxidation numbers of fluorine, oxygen and hydrogen in compounds?
| F | O | H |
A B C D | +7 +1 -7 -1 | -1 +2 -1 -2 | -1 +1 -1 +1 |
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Solutions containing chlorate(I) ions decompose on heating as shown:
3ClO- → ClO3- + 2Cl-
Which row is correct for the oxidation state of the chlorine in each ion?
| ClO- | ClO3- | Cl- |
A B C D | +1 +1 -1 -1 | +5 +3 +5 +3 | -1 +1 -1 +1 |
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A student added a solution of iodine to a solution of sodium bromide. Which statement correctly describes what happens?
No reaction occurs.
The bromide ions are oxidised.
The iodine ions are oxidised.
Both the bromide and iodide ions undergo changes in their oxidation state.
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In which of the following reactions is the change in oxidation number the smallest for nitrogen?
N2 + 3H2 → 2NH3
3Mg + N2 → Mg3N2
4NH3 + 5O2 → 4NO + 6H2O
2NO + O2 → 2NO2
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In the compound [ICl2]+[SbCl6]−, the oxidation number of chlorine is −1.
What are the oxidation numbers of I and Sb in the compound?
| I | Sb |
A B C D | +1 +1 +3 +3 | +5 +7 +5 +7 |
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Titanium dioxide is obtained from the ore ilmenite, Fe(II)TiO3.
FeTiO3 → TiO2
What is the change in the oxidation number of titanium in the reaction?
+4 to +5
+3 to +4
No change in oxidation number occurs
+6 to +4
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In which of the following compounds is the oxidation state of nitrogen the highest?
NaNO2
N2O4
N2O
NO
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In which reaction does an element have the largest change in oxidation number?
Cr2O72- + 6Fe2+ + 14H+ → 2Cr3+ + 6Fe3+ + 7H2O
3ClO– → ClO3– + 2Cl–
5Fe2+ + MnO4– + 8H+ → 5Fe3+ + Mn2+ + 4H2O
PbO2 + Sn2+ + 4H+ → Sn4+ + Pb2+ + 2H2O
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Sulfur dioxide and oxygen difluoride react together. The oxidation number of fluorine in OF2 is -1.
SO2 + OF2 → SO3 + F2
Which row is correct?
| Sulfur | Fluorine | Oxygen in OF2 |
A B C D | Oxidised Reduced Oxidised Reduced | Reduced Oxidised Oxidised Oxidised | Reduced Reduced Reduced Oxidised |
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Oxidation numbers can be used to balance equations. Chlorine and hot aqueous sodium hydroxide react to produce chloride ions, chlorate ions and water.
What are the values of the coefficients p, r and s in the equation?
pCl2 (g) + qOH- (aq) → rCl- (aq) + sClO3- (aq) + tH2O (l)
| p | r | s |
A B C D | 3 3 2 2 | 5 6 5 4 | 1 2 1 2 |
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The chemistry of the Group VII elements often involves redox processes.
Which statement is correct?
Bromine can oxidise chloride ions.
Iodide ions are the weakest reducing agent of the first four Group VII ions.
In reactions with water, chlorine is oxidised and reduced.
Fluorine is a weaker oxidising agent than chlorine.
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Four reactions are shown. In which reaction is the species in bold acting as an oxidising agent?
Cr2O72- + 8H+ + 3SO32- → 2Cr3+ + 4H2O + 3SO42-
Mg + Fe2+ → Mg2+ + Fe
Cl2 + 2Br- → 2Cl- + Br2
Fe2O3 + 3CO → 2Fe + 3CO2
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In which compound are there two different elements with the same oxidation number?
Mg(OH)2
Na2SO4
HClO
NH4Cl
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When sulfuric acid and sodium iodide react one of the reactions that take place is shown by the equation below
8NaI + 9H2SO4 → 8NaHSO4 + 4I2 + H2S + 4H2O
Which species has been oxidised in this reaction?
I-
SO42-
Na+
H+
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The following reaction can be used to determine the mass of titanium dioxide in an ore.
3TiO2 + 4BrF3 → 3TiF4 + 2Br2 + 3O2
Which element increases in oxidation number in this reaction?
Fluorine
Bromine
Titanium
Oxygen
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In which reaction does hydrogen behave as an oxidising agent?
2Na + H2 → 2NaH
N2 + 3H2 → 2NH3
H2 + Cl2 → 2HCl
C2H4 + H2 → C2H6
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Chlorine gas reacts with both hot and cold aqueous sodium hydroxide, each resulting in a different set of products.
What are the oxidation numbers of chlorine in the products of these reactions?
| Hot aqueous sodium hydroxide | Cold aqueous sodium hydroxide |
A B C D | -1, +5 -1, +5 +1, +6 +1, +6 | -1, +1 -1, +2 -1, +1 -1, +2 |
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When solid potassium halides are added to concentrated sulfuric acid, the following reactions take place:
Reaction 1 | 2KBr + 2H2SO4 → K2SO4 + SO2 + Br2 + 2H2O |
Reaction 2 | 8KI + 5H2SO4 → 4K2SO4 + H2S + 4I2 + 4H2O |
Reaction 3 | 2KCl + H2SO4 → K2SO4 + 2HCl |
In each reaction, what is the largest change in the oxidation number of sulfur?
| Reaction 1 | Reaction 2 | Reaction 3 |
A B C D | 1 2 2 4 | 4 4 8 8 | 1 0 0 1 |
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When heated ammonium nitrate, NH4NO3, can decompose explosively.
NH4NO3 → N2O + 2H2O
The nitrogen atoms in NH4NO3 have different oxidation numbers.
What are the changes in the oxidation numbers when this reaction proceeds?
+4, -4
-2, -4
+4, -6
+2, +6
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The acid HIO disproportionate when in aqueous solution, this is shown in the equation, where q, r, s and t are simple whole numbers in their lowest ratios.
q HIO → r I2 + s HIO3 + t H2O
The equation can be balanced using oxidation numbers.
What are the values for r and s?
| r | s |
A | 4 | 2 |
B | 4 | 1 |
C | 2 | 1 |
D | 1 | 2 |
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In winemaking to prevent oxidation of ethanol by air, sulfur dioxide (SO2) is added. In order to calculate the amount of SO2, a sample is titrated with iodine (I2). The reaction is a one to one ratio for SO2 and I2.
What is the change in the oxidation number of sulfur in this reaction?
+2 to +6
+4 to +6
+2 to +4
+4 to +5
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The table shows the redox potentials of a number of species.
Half reaction |
|
V3+ (aq) + e- | - 0.26 |
VO2+ (aq) + 2H+ (aq) + e- | + 0.34 |
S4O62- (aq) + 2e- | + 0.47 |
2VO2+ (aq) + 2H+ (aq) + e- | + 1.00 |
What is the lowest possible oxidation number that Vanadium (V) can be reduced to by thiosulphate ions?
+2
+3
+4
+5
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The oxidation state of chlorine can range from –1 to +7 in its compounds.
Which reagent(s) and conditions are necessary to oxidise elemental chlorine into a compound containing chlorine in the +5 oxidation state?
Concentrated H2SO4 at room temperature.
AgNO3 (aq) followed by NH3 (aq) at room temperature.
Cold dilute NaOH (aq).
Hot concentrated NaOH (aq).
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A student set up experiments to observe the outcome of adding different sodium halides to concentrated phosphoric acid and concentrated sulfuric acid. She recorded her findings in the table below.
| sodium chloride | sodium iodide |
Conc. H3PO4 Conc. H2SO4 | Colourless acidic gas formed Colourless acidic gas formed | Colourless acidic gas formed Purple vapour formed |
Which deduction can be made from these observations?
Concentrated sulfuric acid is a stronger oxidising agent than chlorine.
Concentrated sulfuric acid is a stronger oxidising agent than iodine.
Concentrated phosphoric acid is a stronger oxidising agent than iodine.
Concentrated phosphoric acid is a stronger oxidising agent than concentrated sulfuric acid.
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If a solution contains both bromine and chlorine, BrO3– ions are produced.
The reactions leading to the production of BrO3– ions are shown below:
Reaction 1: Br2 + H2O → HBr + HBrO
Reaction 2: 3HBrO + Cl2 → 2Cl – + BrO3– + Br2 + 3H+
1 | Chlorine is reduced in reaction 2. |
2 | Bromine is reduced in both reaction 1 and reaction 2. |
3 | Bromine is oxidised in both reaction 1 and reaction 2. |
Which statements about these reactions are correct?
1 only
1 and 2
2 and 3
1, 2 and 3
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If a dilute acid is added to an aqueous solution containing nitrite ions, NO2–, two different nitrogen compounds are released as gases.
2H+ (aq) + 2NO2– (aq) → H2O (l) + NO (g) + NO2 (g)
Which of the three statements below correctly describe 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
2 only
2 and 3
1, 2 and 3
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Which pair of reactants will result in a redox reaction?
1 | CH3COCH3 + Tollens’ reagent |
2 | CH3CH2CHO + Fehling’s reagent |
3 | C2H4 + Br2 |
1 only
1 and 2
2 and 3
3 only
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How does concentrated sulfuric acid behave when it reacts with sodium chloride?
As a reducing agent only.
As an oxidising agent only.
As an acid only.
As an acid and an oxidizing agent.
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V2+ (aq)