Syllabus Edition
First teaching 2014
Last exams 2024
Which row correctly describes oxidation and reduction in terms of the transfer of electrons and changes in oxidation state?
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Transfer of electrons |
Change in oxidation state |
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oxidation |
reduction |
oxidation |
reduction |
|
A B C D |
gain loss loss gain |
loss gain gain loss |
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?
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|
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?
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|
ClO- |
ClO3- |
Cl- |
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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 atoms 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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Below are four statements about voltaic and electrolytic cells. Identify the statement that is correct for voltaic cells but not for electrolytic cells
An electrolyte is needed in the cell
Ions are moving in the electrolyte
Oxidation occurs at the anode
Electrons flow from the negative to the positive electrode
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What substance will be obtained at the positive electrode (anode) when molten KBr is electrolysed?
K(l)
Br(l)
Br2(l)
K(s)
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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)
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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 of the following statements 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 below. In which reaction is the species shown 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 takes 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 oxidizing agent?
2Na + H2 → 2NaH
N2 + 3H2 → 2NH3
H2 + Cl2 → 2HCl
C2H4 + H2 → C2H6
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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 |
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reaction 2 |
8KI + 5H2SO4 → 4K2SO4 + H2S + 4I 2 + 4H2O |
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reaction 3 |
2KCl + H2SO4 → K2SO4 + 2HCl |
In each reaction, what is the largest change in the oxidation number of sulfur?
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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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What is formed at the electrodes during the electrolysis of molten potassium iodide?
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Positive electrode |
Negative electrode |
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A |
K+ |
I- |
|
B |
K |
I2 |
|
C |
I- |
K+ |
|
D |
I2 |
K |
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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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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 oxidation numbers for each of the N atoms when this reaction proceeds?
+4, –4
–2, –4
+4, –6
+2, +6
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In winemaking, to prevent the 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 to produce H2SO4 as well as another product.
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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20 cm3 of a 0.60 mol dm–3 solution of thallium nitrate (TlNO3) requires 40 cm3 of
0.20 mol dm–3 acidified ammonium metavanadate (NH4VO3) to produce Tl3+(aq) ions.
Vanadium is the only element reduced in this reaction. What is the change in oxidation number of vanadium?
+1
+2
+3
+4
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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+
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1 |
Chlorine is reduced in reaction 2 |
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2 |
Bromine is reduced in both reaction 1 and reaction 2 |
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3 |
Bromine is oxidised in both reaction 1 and reaction 2 |
Which statements about these reactions are correct?
1 only
1 and 2 only
2 and 3 only
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?
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1 |
The H+(aq) ion is oxidised by NO2–(aq). |
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2 |
Some nitrogen atoms are oxidised, and some nitrogen atoms are reduced |
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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?
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Anode (negative electrode) |
Cathode ( positive electrode) |
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A |
Ag(s) → Ag+ (aq) + e- |
Zn2+(aq) + 2e- → Zn(s) |
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B |
Ag+(aq) + e-→ Ag(s) |
Zn(s) → Zn2+(aq) + 2e- |
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C |
Zn(s) → Zn2+(aq) + 2e- |
Ag+(aq) + e-→ Ag(s) |
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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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When molten magnesium chloride is electrolysed using graphite electrodes what are the products?
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Product at cathode (negative electrode) |
Product at anode ( positive electrode) |
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A |
magnesium |
chlorine |
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B |
chlorine |
magnesium |
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C |
magnesium ions |
chloride ions |
|
D |
chloride ions |
magnesium ions |
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Use the information given about four reactions of metals to determine the order of reactivity from most reactive to least reactive
W(s) + X2+(aq) → W2+(aq) + X(s)
Y(s) + W2+(aq) → No Reaction
X(s) + Y2+(aq) → X2+(aq) + Y(s)
Z(s) + Y2+(aq) → No Reaction
W > Y > X > Z
X > W > Z > Y
Z > Y > W > X
W > X > Y > Z
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Below are three statements about voltaic cells.
The correct statements are
I and II only
I and III only
II and III only
I, II and III
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