06 Redox Chemistry, Set A To print: Ctrl + P, paper A4, margins Default.
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06

Redox Chemistry

Set AConcept Practice
Name
Time 55 minutes
Total 46 marks
A

From the lesson

29 marks
1

In which species does nitrogen have an oxidation state of +3?

ANO2
BNO2−
CNH4+
DN2O
Answer [1]

Learners' Alley, Redox Chemistry slides

2

Which reaction is not a redox reaction?

AMg + 2HCl → MgCl2 + H2
BCaCO3 + 2HCl → CaCl2 + H2O + CO2
CCl2 + 2KBr → 2KCl + Br2
DCuO + H2 → Cu + H2O
Answer [1]

Learners' Alley, Redox Chemistry slides

3

A colourless gas turns a filter paper spotted with aqueous potassium iodide yellow-brown. What can be deduced?

AThe gas is an oxidising agent.
BThe gas is a reducing agent.
CThe iodide ions are reduced.
DThe gas is iodine.
Answer [1]

Learners' Alley, Redox Chemistry slides

4

Which reaction is a disproportionation?

A2Pb(NO3)2 → 2PbO + 4NO2 + O2
BCl2 + 2NaOH → NaCl + NaClO + H2O
CZn + CuSO4 → ZnSO4 + Cu
DMgO + 2HCl → MgCl2 + H2O
Answer [1]

Learners' Alley, Redox Chemistry slides

5

How many moles of MnO4− react with 1.0 × 10−3 mol of Fe2+ in acid?

A2.0 × 10−4
B5.0 × 10−4
C1.0 × 10−3
D5.0 × 10−3
Answer [1]

Learners' Alley, Redox Chemistry slides

6

Sodium burns in chlorine: 2Na + Cl2 → 2NaCl.

(a)
Write the two half-equations.
[1]
(b)
Which reactant is oxidised? Explain.
[1]

Learners' Alley, Redox Chemistry slides

7
In CuO + H2 → Cu + H2O, which substance is reduced? Explain in terms of oxygen.
[1]

Learners' Alley, Redox Chemistry slides

8

Find the oxidation state of

(a)
chromium in Cr2O72−
[1]
(b)
sulfur in Na2S2O3
[1]
(c)
hydrogen in NaH
[1]
(d)
vanadium in VO2+
[1]

Learners' Alley, Redox Chemistry slides

9

Which of these are redox reactions? Explain using oxidation states.

(a)
NH3 + HNO3 → NH4NO3
[1]
(b)
CuCO3 → CuO + CO2
[1]
(c)
2Cu(NO3)2 → 2CuO + 4NO2 + O2
[1]

Learners' Alley, Redox Chemistry slides

10

Sulfur dioxide decolourises acidified potassium manganate(VII) and turns acidified potassium dichromate(VI) green.

State whether each of the three substances acts as an oxidising agent or a reducing agent.
[2]

Learners' Alley, Redox Chemistry slides

11
Iron(III) ions oxidise iodide ions and are reduced to iron(II) ions. Write the ionic equation.
[1]

Learners' Alley, Redox Chemistry slides

12
Write the balanced equation for acidified dichromate(VI) ions oxidising iron(II) ions.
[2]

Learners' Alley, Redox Chemistry slides

13
25.0 cm3 of 0.100 mol dm−3 NH2OH reacts exactly with 25.0 cm3 of 0.200 mol dm−3 Mn3+, which is reduced to Mn2+. Nitrogen in NH2OH is −1. Find its final oxidation state.
[2]

Learners' Alley, Redox Chemistry slides

14
Is 2NO2 + H2O → HNO3 + HNO2 a disproportionation? Give the oxidation states of nitrogen.
[2]

Learners' Alley, Redox Chemistry slides

15
25.0 cm3 of an acidified iron(II) solution needs 20.00 cm3 of 0.0200 mol dm−3 KMnO4. Find the concentration of the iron(II) ions.
[2]

Learners' Alley, Redox Chemistry slides

16
12.0 g of FeSO4·(NH4)2SO4·xH2O is made up to 250 cm3. 25.0 cm3 of this solution needs 25.50 cm3 of 0.0200 mol dm−3 K2Cr2O7. Find x.
[3]

Learners' Alley, Redox Chemistry slides

B

Practice

17 marks
17

Which formula contains nitrogen with an oxidation state of +5?

ANO2
BN2O4
CNH4+
DHNO3
Answer [1]

2023 XMS O Prelim P1 Q28

18

In which substance does the nitrogen atom have the same oxidation state as the nitrogen atom in HNO2?

ANF3
BNH4+
CNO
DNO2+
Answer [1]

2024 Woodlands O Prelim P1 Q19

19

Which oxidation state of the underlined element is correct?

substanceoxidation state
AHNO3+3
BCaSO4+6
CFeO−3
DNaHCO3+3
Arow A
Brow B
Crow C
Drow D
Answer [1]

2024 Zhonghua O Prelim P1 Q21

20

In which substance does the sulfur atom have the same oxidation number as the sulfur atom in SO2?

AH2SO4
BK2SO3
CNa2S
DNa2S2O3
Answer [1]

2024 CHIJ O Prelim P1 Q22

21

The oxide of titanium, TiO2, is used as a ‘whitener’ in toothpaste. It is obtained from the ore iron(II) titanate, FeTiO3. What is the change in the oxidation number of titanium from FeTiO3 to TiO2?

A+3 to +2
B+3 to +4
C+6 to +4
Dno change
Answer [1]

2022 SJI O Prelim P1 Q24

22

In which reaction does the oxidation state of iron remain unchanged?

AFe + 2FeCl3 → 3FeCl2
BFe2O3 + 6HCl → 2FeCl3 + 3H2O
C2Fe + 3Cl2 → 2FeCl3
D2FeCl2 + Cl2 → 2FeCl3
Answer [1]

2024 AMKSS O Prelim P1 Q21

23

Which method of preparation of magnesium sulfate is an example of a redox reaction?

AMg + H2SO4 → MgSO4 + H2
BMgO + H2SO4 → MgSO4 + H2O
CMg(OH)2 + H2SO4 → MgSO4 + 2H2O
DMgCO3 + H2SO4 → MgSO4 + H2O + CO2
Answer [1]

2024 ANDSS O Prelim P1 Q17

24

Which reaction is not a redox reaction?

AMg + 2HNO3 → Mg(NO3)2 + H2
B2Mg(NO3)2 → 2MgO + 4NO2 + O2
CSO2 + NO2 → SO3 + NO
DSO3 + H2O → H2SO4
Answer [1]

2024 SCSS O Prelim P1 Q20

25

Iron(II) chloride solution reacts with chlorine gas: 2FeCl2(aq) + Cl2(g) → 2FeCl3(aq). Which statements about this reaction are correct?

1 Fe2+ ions are reduced to Fe3+ ions.
2 Chlorine acts as a reducing agent.
3 Fe2+ ions each lose an electron.
4 Cl2 molecules are reduced to Cl− ions.

A1 and 2 only
B2 and 3 only
C2 and 4 only
D3 and 4 only
Answer [1]

2024 Zhenghua O Prelim P1-P3 Q24

26

The reaction between copper and concentrated nitric acid is shown: Cu + 4HNO3 → Cu(NO3)2 + 2H2O + 2NO2. Which statement about this reaction is correct?

AHNO3 is a reducing agent.
BThe oxidation state of nitrogen in Cu(NO3)2 is −5.
CCu loses electrons during the reaction.
DThe oxidation state of oxygen has changed.
Answer [1]

2025 MSHS O Prelim P1 Q15

27

Acidified potassium manganate(VII) can be used to detect ethanol vapour in the breath of a person who has drunk alcohol. The acidified potassium manganate(VII) turned from purple to colourless in the presence of ethanol vapour. Which explanation is correct?

AEthanol has been oxidised.
BEthanol is an oxidising agent.
CAcidified potassium manganate(VII) has been oxidised.
DAcidified potassium manganate(VII) is a reducing agent.
Answer [1]

2024 PLMGSS O Prelim P1 Q26

28

The equation for the reaction between sodium sulfite and potassium manganate(VII) is shown: 2MnO4− + 6H+ + 5SO32− → 2Mn2+ + 3H2O + 5SO42−. Which ion is reduced and what is the reducing agent?

ion that is reducedreducing agent
AMnO4−H+
BMnO4−SO32−
CSO32−H+
DSO32−MnO4−
Arow A
Brow B
Crow C
Drow D
Answer [1]

2025 JYSS O Prelim P1 Q23

29

Colour changes are often seen when redox reactions occur. Which colour change is due to the reduction of the underlined reagent?

ACuO changes to CuSO4
BKI changes to I2
CFeCl2 changes to FeCl3
DMnO4− changes to Mn2+
Answer [1]

2024 NASS O Prelim P1-P2 Q25

30

When chlorine gas dissolves in water a reaction occurs: Cl2 + H2O → HCl + HClO. Which row shows the oxidation number of chlorine in the chlorine-containing species?

Cl2HClHClO
A−1−1−1
B0−1−1
C−1+1+1
D0−1+1
Arow A
Brow B
Crow C
Drow D
Answer [1]

2024 USS O Prelim P2 Q28

31

Disproportionation is a reaction in which the same element is both oxidised and reduced. Which reaction is an example of disproportionation?

ACu + 2H2SO4 → CuSO4 + 2H2O + SO2
BCl2 + 2NaOH → NaCl + NaOCl + H2O
CMgO + 2HCl → MgCl2 + H2O
D2Pb(NO3)2 → 2PbO + 4NO2 + O2
Answer [1]

2024 Bukit View O Prelim P1 Q24

32

Substance X, which is not brown, was bubbled into a solution containing sodium iodide and sodium chloride. The solution turned brown. Which statements can be deduced about substance X?

1 Substance X is an oxidising agent.
2 Substance X must be bromine gas.
3 The iodide in the solution was reduced to aqueous iodine.

A1 only
B1 and 2 only
C1 and 3 only
D2 and 3 only
Answer [1]

2023 XMS O Prelim P1 Q25

33

Some statements about acids are given below.

I pH is a measure of the H+ concentration in a solution.
II The strength of an acid depends on its concentration.
III Universal Indicator turns orange when placed in a solution of any acid.
IV When acids react with metals, hydrogen ions gain electrons.

Which statements about acids are correct?

AI and II only
BI and IV only
CI, II and III
DI, II and IV
Answer [1]

2024 SMSS O Sec3 P1 Q11

The Periodic Table of Elements, from the A Level Chemistry Data Booklet (8873, 9476, 9813)