WorksheetsRedox Reactions Quiz
Total questions: 100
Worksheet time: 50mins
Which of the following best describes a redox reaction?
A reaction where only oxidation occurs
A reaction where only reduction occurs
A reaction in which oxidation and reduction reactions occur simultaneously
A reaction that does not involve electron transfer
What is the term used for a substance that causes oxidation in a redox reaction?
Reductant
Oxidant
Catalyst
Solvent
Which process is explained by the transfer of electrons in redox reactions?
Precipitation
Electron transfer process
Filtration
Distillation
Which concept is used to identify the oxidant and reductant in a reaction?
Atomic mass
Oxidation number
Molarity
pH value
Which of the following is NOT a type of redox reaction classification mentioned in the objectives?
Combination (synthesis)
Decomposition
Displacement
Neutralization
Why do many elements commonly undergo oxidation on earth?
Due to the presence of water
Due to the presence of dioxygen in the atmosphere (~20%)
Due to high temperature
Due to the presence of nitrogen
Which environmental issue is associated with redox reactions as mentioned in the text?
Acid rain
Hydrogen Economy
Global warming
Deforestation
Given the reaction: 2 Mg (s) + O₂ (g) → 2 MgO (s), which element is being oxidized?
Magnesium
Oxygen
Sulfur
Nitrogen
Suggest a comparative order among various reductants and oxidants. What skill does this task require?
Recall of facts
Application of concepts
Strategic thinking and reasoning
Simple calculation
Why is the development of the 'Ozone Hole' considered under redox phenomenon?
It involves only physical changes
It involves oxidation and reduction processes
It is caused by temperature changes
It is unrelated to chemical reactions
Which of the following best defines oxidation according to modern chemistry?
Addition of hydrogen to a substance or removal of oxygen from a substance.
Addition of oxygen/electronegative element to a substance or removal of hydrogen/electropositive element from a substance.
Removal of electrons from a substance only.
Addition of chlorine to any compound.
Which reaction below is an example of oxidation due to the removal of hydrogen?
CH₄ (g) + 2O₂ (g) → CO₂ (g) + 2H₂O (l)
2 H₂S (g) + O₂ (g) → 2 S (s) + 2 H₂O (l)
Mg (s) + F₂ (g) → MgF₂ (s)
2 HgO (s) → 2 Hg (l) + O₂ (g)
Which of the following reactions illustrates oxidation by the addition of an electronegative element?
Mg (s) + F₂ (g) → MgF₂ (s)
2 FeCl₃ (aq) + H₂ (g) → 2 FeCl₂ (aq) + 2 HCl (aq)
CH₂ = CH₂ (g) + H₂ (g) → H₃C – CH₃ (g)
2 Na (s) + H₂ (g) → 2 NaH (s)
According to the text, what is the modern definition of reduction?
Addition of oxygen/electronegative element to a substance.
Removal of oxygen/electronegative element from a substance or addition of hydrogen/electropositive element to a substance.
Removal of hydrogen from a substance.
Addition of chlorine to a substance.
Which process is described by the reaction: 2 HgO (s) → 2 Hg (l) + O₂ (g)?
Oxidation of mercury oxide
Reduction of mercury oxide
Oxidation of oxygen
Reduction of oxygen
Why was the term "redox" coined for a class of chemical reactions?
Because only oxidation occurs in these reactions.
Because only reduction occurs in these reactions.
Because oxidation and reduction always occur simultaneously.
Because hydrogen is always removed in these reactions.
In the reaction CH₂ = CH₂ (g) + H₂ (g) → H₃C – CH₃ (g), what type of chemical change is occurring?
Addition of oxygen
Addition of hydrogen
Removal of chlorine
Removal of oxygen
Which of the following reactions is interpreted as oxidation due to the removal of an electropositive element?
2K₄[Fe(CN)₆](aq) + H₂O₂ (aq) → 2K₃[Fe(CN)₆](aq) + 2 KOH (aq)
Mg (s) + S (s) → MgS (s)
2 HgO (s) → 2 Hg (l) + O₂ (g)
2 Na (s) + H₂ (g) → 2 NaH (s)
In the reaction 2 FeCl₃ (aq) + H₂ (g) → 2 FeCl₂ (aq) + 2 HCl (aq), what is being removed from ferric chloride?
Oxygen
Hydrogen
Chlorine
Mercury
Which statement best explains why aluminium is oxidised in the reaction 3Fe₃O₄ (s) + 8 Al (s) → 9 Fe (s) + 4Al₂O₃ (s)?
Aluminium loses hydrogen.
Aluminium gains oxygen.
Aluminium loses chlorine.
Aluminium gains mercury.
Which of the following reactions is an example of a redox reaction?
2Na(s) + Cl₂(g) → 2NaCl(s)
H₂O(l) → H₂(g) + O₂(g)
NaCl(s) → Na⁺(aq) + Cl⁻(aq)
CO₂(g) → C(s) + O₂(g)
What is the definition of oxidation in terms of electron transfer?
Gain of electron(s) by any species
Loss of electron(s) by any species
Acceptance of electron(s) by any species
Donation of electron(s) by any species
Which species acts as a reducing agent in the reaction 2Na(s) + Cl₂(g) → 2NaCl(s)?
Sodium (Na)
Chlorine (Cl₂)
Sodium chloride (NaCl)
Oxygen (O₂)
In the reaction 2Na(s) + Cl₂(g) → 2NaCl(s), what happens to chlorine?
It loses electrons and is oxidized
It gains electrons and is reduced
It remains unchanged
It acts as a reducing agent
Which of the following best describes an oxidising agent?
Donor of electron(s)
Acceptor of electron(s)
Loses electron(s)
Gains electron(s)
Given the reaction 2Na(s) + H₂(g) → 2NaH(s), justify why it is a redox reaction.
Because sodium is reduced and hydrogen is oxidized
Because sodium is oxidized and hydrogen is reduced
Because both sodium and hydrogen are oxidized
Because both sodium and hydrogen are reduced
Which of the following is NOT a correct statement about redox reactions?
Oxidation involves loss of electrons
Reduction involves gain of electrons
Oxidising agent donates electrons
Reducing agent donates electrons
How can the formation of sodium chloride be represented in terms of electron transfer?
2Na(s) → 2Na⁺(g) + 2e⁻; Cl₂(g) + 2e⁻ → 2Cl⁻(g)
2Na⁺(g) + 2e⁻ → 2Na(s); Cl₂(g) → 2Cl⁻(g) + 2e⁻
2Na(s) + Cl₂(g) → 2NaCl(s) + 2e⁻
2Na(s) + 2Cl⁻(g) → 2NaCl(s) + 2e⁻
Which of the following best describes what happens when a strip of metallic zinc is placed in an aqueous solution of copper nitrate?
The zinc strip dissolves and the solution turns green.
The zinc strip becomes coated with copper and the blue colour of the solution disappears.
The zinc strip remains unchanged and the solution turns yellow.
The zinc strip reacts to form a white precipitate and the solution turns red.
In the reaction Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s), which species is oxidised?
Copper
Zinc
Zinc ion
Copper ion
Which of the following reactions shows the release and gain of 2 electrons during a redox process?
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)
H₂(g) + O₂(g) → H₂O(l)
Na(s) + Cl₂(g) → NaCl(s)
Fe(s) + S(s) → FeS(s)
Why does the blue colour of the solution disappear when zinc is placed in copper nitrate solution?
Because zinc forms a blue complex with nitrate ions.
Because Cu²⁺ ions are reduced and deposited as copper metal.
Because zinc nitrate is blue in colour.
Because the solution is diluted with water.
(DoK Level 2) If hydrogen sulphide gas is passed through a colourless solution containing Zn²⁺ ions, what observation would you expect?
Formation of a blue precipitate.
Appearance of white zinc sulphide (ZnS).
Evolution of hydrogen gas.
Formation of a black precipitate.
(DoK Level 2) In the electron transfer reaction between copper metal and silver nitrate solution, what is the role of Ag⁺ ions?
They act as an oxidising agent and are reduced to Ag(s).
They act as a reducing agent and are oxidised to Ag(s).
They remain unchanged in the solution.
They form a complex with copper ions.
(DoK Level 3) Given the reaction: Co(s) + Ni²⁺(aq) → Co²⁺(aq) + Ni(s), explain why cobalt is oxidised and nickel is reduced.
Cobalt loses electrons to form Co²⁺, while nickel gains electrons to form Ni(s).
Cobalt gains electrons to form Co²⁺, while nickel loses electrons to form Ni(s).
Both cobalt and nickel are oxidised.
Both cobalt and nickel are reduced.
(DoK Level 3) Why does equilibrium for the reaction Cu(s) + 2Ag⁺(aq) → Cu²⁺(aq) + 2Ag(s) greatly favour the products over the reactants?
Because Ag⁺ is a stronger oxidising agent than Cu²⁺.
Because Cu²⁺ is a stronger oxidising agent than Ag⁺.
Because copper metal is more reactive than silver metal.
Because silver metal is more reactive than copper metal.
Which metal releases electrons more easily: zinc, copper, or silver?
Zinc
Copper
Silver
Gold
What is the name of the series that lists metals and their ions based on their tendency to release electrons?
Activity series
Periodic series
Electrochemical series
Galvanic series
In the reaction 2H₂(g) + O₂(g) → 2H₂O(l), which element is oxidised?
Hydrogen
Oxygen
Nitrogen
Carbon
What does the oxidation number of an element in a compound represent?
The number of protons in the element
The oxidation state ascertained by a set of rules based on electron pair shifts
The atomic mass of the element
The number of neutrons in the element
Why is the concept of oxidation number useful in chemical reactions involving covalent compounds?
It helps keep track of electron shifts
It determines the melting point
It predicts the color of compounds
It measures the solubility of compounds
Given the reaction CH₄(g) + 4Cl₂(g) → CCl₄(l) + 4HCl(g), what is the oxidation number of carbon in CH₄ and CCl₄ respectively?
-4 in CH₄ and +4 in CCl₄
+4 in CH₄ and -4 in CCl₄
0 in both CH₄ and CCl₄
+1 in CH₄ and -1 in CCl₄
What is the main source of electrical energy in Galvanic cells?
Chemical reactions between metals
Physical mixing of solutions
Heating of metals
Light absorption
What is observed when a copper rod is dipped in silver nitrate solution?
Blue color starts developing and silver deposits on the rod
Red color appears and gold deposits on the rod
No color change and no deposits
Green color develops and copper deposits on the rod
What is the oxidation number of an element in its free or uncombined state?
Zero
+1
-1
+2
Which of the following ions has an oxidation number of +2?
Na⁺
Mg²⁺
Fe³⁺
Cl⁻
In most compounds, what is the oxidation number of oxygen?
+2
-1
-2
0
Which compound contains oxygen with an oxidation number of -1?
H₂O
Na₂O₂
CO₂
OF₂
What is the oxidation number of hydrogen in most compounds, except when bonded to metals in binary compounds?
-1
0
+1
+2
Fluorine has an oxidation number of -1 in all its compounds. Which other halogens also have an oxidation number of -1 when they occur as halide ions?
Chlorine, bromine, and iodine
Oxygen, nitrogen, and sulfur
Sodium, potassium, and calcium
Carbon, silicon, and phosphorus
What must the algebraic sum of the oxidation numbers of all atoms in a compound equal?
The atomic number
Zero
The mass number
The number of electrons
In the carbonate ion (CO₃)²⁻, what is the sum of the oxidation numbers of the three oxygen atoms and one carbon atom?
+2
-2
0
+4
How does the highest oxidation number exhibited by an atom of an element generally change across the period in the periodic table?
It decreases
It remains constant
It increases
It fluctuates randomly
What term is often used interchangeably with the oxidation number?
Atomic mass
Oxidation state
Valency
Electronegativity
If the oxidation number of carbon in CO₂ is +4, what is the oxidation number of oxygen in the same compound?
+2
-2
0
-1
Why is it necessary to use a set of rules to determine the oxidation number of an element in a compound or ion?
Because elements are always neutral
Because it is not always possible to remember or make out easily which element is more electronegative
Because all elements have the same oxidation number
Because oxidation numbers are not important
Which of the following elements has the highest oxidation number of +7 in its group?
Na
Cl
Mg
Al
According to Stock notation, how is the oxidation number of a metal in a compound represented?
By using a subscript after the metal symbol
By putting a Roman numeral in parenthesis after the symbol of the metal
By using a prefix before the metal symbol
By underlining the metal symbol
Which compound is correctly represented in Stock notation as Fe(III)₂O₃?
FeO
Fe₂O₃
CuO
MnO
What is the oxidation number of copper in CuO?
0
1
2
3
Which statement best describes oxidation in terms of oxidation number?
A decrease in the oxidation number of the element
An increase in the oxidation number of the element
No change in the oxidation number of the element
The element gains electrons
Which of the following acts as an oxidising agent?
A reagent that decreases the oxidation number of an element
A reagent that increases the oxidation number of an element
A reagent that does not change the oxidation number
A reagent that only reacts with metals
In the reaction 2Cu₂O(s) + Cu₂S(s) → 6Cu(s) + SO₂(g), which element is oxidised?
Copper
Sulphur
Oxygen
Sodium
Using Stock notation, how would you represent MnO₂?
Mn(II)O₂
Mn(IV)O₂
Mn(III)O₂
Mn(I)O₂
Which of the following is a correct definition of a redox reaction?
A reaction that involves only the transfer of electrons
A reaction that involves a change in oxidation number of the interacting species
A reaction that involves only the formation of precipitate
A reaction that does not involve any change in oxidation number
In the reaction 2Cu₂O(s) + Cu₂S(s) → 6Cu(s) + SO₂(g), what happens to copper?
Copper is oxidised from +1 to +2 state
Copper is reduced from +1 to 0 state
Copper is reduced from +2 to 0 state
Copper is oxidised from 0 to +1 state
Which of the following is a characteristic of a combination reaction in redox chemistry?
Two or more reactants combine to form a single product, often involving elemental forms.
A single compound breaks down into two or more products.
An ion in a compound is replaced by another ion.
Only non-metal elements are involved.
Which of the following is an example of a decomposition reaction?
C(s) + O₂(g) → CO₂(g)
2H₂O(l) → 2H₂(g) + O₂(g)
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)
3Mg(s) + N₂(g) → Mg₃N₂(s)
In a displacement reaction, what happens?
Two elements combine to form a compound.
A compound breaks down into simpler substances.
An ion or atom in a compound is replaced by an ion or atom of another element.
Only non-metals are involved.
Which of the following reactions is a metal displacement reaction?
2NaH(s) → 2Na(s) + H₂(g)
CuSO₄(aq) + Zn(s) → Cu(s) + ZnSO₄(aq)
2KClO₃(s) → 2KCl(s) + 3O₂(g)
CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l)
Which statement best describes the difference between combination and decomposition reactions in redox chemistry?
Combination reactions break down compounds, while decomposition reactions form compounds.
Combination reactions involve the formation of a single product from multiple reactants, while decomposition reactions involve the breakdown of a compound into two or more products.
Both reactions always involve only metals.
Decomposition reactions always require oxygen.
Why is the reducing metal in a metal displacement reaction considered a better reducing agent than the metal being reduced?
It has a higher atomic number.
It shows more capability to lose electrons compared to the one that is reduced.
It is always a non-metal.
It forms more stable compounds.
Which of the following is NOT a redox reaction?
C(s) + O₂(g) → CO₂(g)
2KClO₃(s) → 2KCl(s) + 3O₂(g)
CaCO₃(s) → CaO(s) + CO₂(g)
3Mg(s) + N₂(g) → Mg₃N₂(s)
In the reaction 2NaH(s) → 2Na(s) + H₂(g), what is the oxidation state of hydrogen in NaH?
+1
0
-1
+2
Which type of redox reaction involves the breakdown of a compound into two or more components, at least one of which must be in the elemental state?
Combination reaction
Decomposition reaction
Displacement reaction
Precipitation reaction
What is the general form of a displacement reaction?
A + B → C
X + YZ → XZ + Y
AB → A + B
X + Y → XY
Which alkali metals and alkaline earth metals are capable of displacing hydrogen from cold water?
Sodium, calcium, strontium, barium
Zinc, copper, silver, gold
Iron, magnesium, tin, cadmium
Chlorine, bromine, iodine, fluorine
What is the product when magnesium reacts with steam?
Mg(OH)₂(s) and H₂(g)
MgCl₂(aq) and H₂(g)
Fe₂O₃(s) and H₂(g)
ZnCl₂(aq) and H₂(g)
Which metal does NOT react with hydrochloric acid?
Silver
Magnesium
Zinc
Iron
Arrange the following metals in order of decreasing tendency to lose electrons: Zn, Cu, Ag.
Zn > Cu > Ag
Ag > Cu > Zn
Cu > Zn > Ag
Zn > Ag > Cu
Which halogen is the strongest oxidising agent?
Fluorine
Chlorine
Bromine
Iodine
Why are displacement reactions using fluorine not generally carried out in aqueous solution?
Fluorine is too reactive and attacks water, displacing its oxygen.
Fluorine is insoluble in water.
Fluorine does not react with halides.
Fluorine forms a precipitate in water.
Which reaction is used to identify Br⁻ and I⁻ ions in the laboratory through the Layer Test?
Cl₂(g) + 2KBr(aq) → 2KCl(aq) + Br₂(l)
Mg(s) + 2H₂O(l) → Mg(OH)₂(s) + H₂(g)
Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g)
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
What is the general oxidation process for the recovery of halogens from their halides?
2X⁻ → X₂ + 2e⁻
X₂ + 2e⁻ → 2X⁻
2X + 2e⁻ → X₂
X₂ → 2X⁻ + 2e⁻
Which of the following metals can displace hydrogen from acids but not from cold water?
Zinc
Sodium
Calcium
Strontium
What is the product when chlorine gas reacts with potassium iodide solution?
2KCl(aq) + I₂(s)
2KCl(aq) + Br₂(l)
KCl(aq) + HF(aq)
MgCl₂(aq) + H₂(g)
Which of the following is a characteristic of a disproportionation reaction?
An element is only oxidized.
An element is only reduced.
An element is simultaneously oxidized and reduced.
No change in oxidation state occurs.
In the decomposition of hydrogen peroxide (2H₂O₂ → 2H₂O + O₂), what happens to the oxidation state of oxygen?
It remains the same.
It increases from -1 to 0.
It decreases from 0 to -2.
It increases from -2 to +1.
Which element among halogens does NOT show disproportionation tendency?
Chlorine
Bromine
Fluorine
Iodine
Why does ClO₄⁻ not undergo disproportionation?
It is in its lowest oxidation state.
It is in its highest oxidation state (+7).
It is a neutral molecule.
It is a reducing agent.
Which of the following reactions is an example of disproportionation?
2H₂O₂(aq) → 2H₂O(l) + O₂(g)
N₂(g) + O₂(g) → 2NO(g)
2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g)
NaHS(aq) + H₂O(l) → NaOH(aq) + H₂(g)
Given the reaction: 3ClO⁻ → 2Cl⁻ + ClO₃⁻, what are the oxidation states of chlorine in ClO⁻, Cl⁻, and ClO₃⁻ respectively?
+1, -1, +5
-1, +1, +5
+5, +1, -1
+1, +5, -1
Suggest a scheme of classification for the following redox reaction: 2NO₂(g) + 2OH⁻(aq) → NO₂⁻(aq) + NO₃⁻(aq) + H₂O(l)
Combination reaction
Disproportionation reaction
Decomposition reaction
Double displacement reaction
Which type of redox reaction involves the combination of elemental substances to form a compound?
Combination redox reaction
Decomposition redox reaction
Displacement redox reaction
Disproportionation redox reaction
What is the oxidation number of carbon in C₃O₂?
4/3
2
1
3
In Br₃O₈, what is the average oxidation number of bromine?
16/3
8
2.5
4
What is the average oxidation number of sulphur in Na₂S₄O₆?
2.5
4
3
6
Why is the idea of fractional oxidation number considered unconvincing?
Because electrons are never shared/transferred in fraction
Because oxidation numbers are always integers
Because only metals can have fractional oxidation numbers
Because it only applies to gases
Which redox reaction involves the breakdown of a compound into three components?
Decomposition redox reaction
Combination redox reaction
Displacement redox reaction
Disproportionation redox reaction
In the structure of C₃O₂, what are the oxidation states of the two terminal carbon atoms?
+2
0
-2
+4
