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WorksheetsMostly Electrochemistry and Redox
Total questions: 146
Worksheet time: 5hrs 52mins
Given the unbalanced equation Cr⁰ + Sn²⁺ → Cr³⁺ + Sn⁰ What is the coefficient in front of the Cr³⁺ when the equation is balanced using smallest whole-number coefficients?
1
2
3
6
What is the total number of moles of electrons needed to completely reduce 6.0 moles of Ni²⁺(aq) ions?
6.0 moles
3.0 moles
12.0 moles
1.0 mole
Given the balanced ionic equation: 2Al(s) + 3Cu²⁺(aq) → 2Al³⁺(aq) + 3Cu(s) Compared to the total charge of the reactants, the total charge of the products is
less
greater
the same
Which half-reaction shows conservation of charge?
Cu + e⁻ → Cu⁺
Cu²⁺ + 2e⁻ → Cu
Cu⁺ → Cu + e⁻
Cu²⁺ → Cu + 2e⁻
Base your answer(s) to the following question(s) on the diagram below. The diagram shows a voltaic cell with copper and aluminum electrodes immediately after the external circuit is completed. Balance the redox equation using the smallest whole-number coefficients. ____ Cu2+(aq) + ____ Al(s) → ____ Cu(s) + ____ Al3+(aq) Fill in the blank for the coefficient of Cu2+(aq).
3
1
2
6
Base your answer(s) to the following question(s) on the diagram below. The diagram shows a voltaic cell with copper and aluminum electrodes immediately after the external circuit is completed. Balance the redox equation using the smallest whole-number coefficients. __Cu2+(aq) + ____ Al(s) → 3 Cu(s) + ____ Al3+(aq) What is the coefficient of Al(s)?
2
1
3
6
In a redox reaction, the total number of electrons lost is
less than the total number of electrons gained
greater than the total number of electrons gained
equal to the total number of electrons gained
equal to the total number of protons gained
Balance the equation below for the redox reaction that occurs in this cell, using the smallest whole-number coefficients. ______ Zn(s) + ______ Fe³⁺(aq) → ______ Zn²⁺ + ______ Fe(s)
3 Zn(s) + 2 Fe³⁺(aq) → 3 Zn²⁺ + 2 Fe(s)
2 Zn(s) + 3 Fe³⁺(aq) → 2 Zn²⁺ + 3 Fe(s)
2 Zn(s) + 3 Fe³⁺(aq) → 2 Zn²⁺ + 3 Fe(s)
2 Zn(s) + Fe³⁺(aq) → 2 Zn²⁺ + Fe(s)
Which equation represents conservation of charge?
I⁻ + 2e⁻ → I₂
2I⁻ → I₂ + 2e⁻
Br₂ → 2Br⁻ + 2e⁻
Br + 2e⁻ → Br⁻
The balanced, half-reaction equation for the reduction of the copper ions is:
Cu²⁺ + 2e⁻ → Cu(s)
Cu(s) → Cu²⁺ + 2e⁻
Cu⁺ + e⁻ → Cu(s)
Cu²⁺ → Cu(s) + 2e⁻
For which chemical reaction must an electrolytic cell be used?
AgNO3 + NaCl → AgCl + NaNO3
Cu + FeCl2 → CuCl2 + Fe
Zn + 2HCl → ZnCl2 + H2
2Al + 3Ni(NO3)2 → 2Al(NO3)3 + 3Ni
A metal that is usually obtained from its fused compound by electrolytic reduction is
copper
iron
zinc
sodium
Which metal is obtained from its fused salt by electrolysis?
Ca
Cr
Pb
Pt
The diagram pictured shows a spoon that will be electroplated with nickel metal. What will occur when switch S is closed?
The spoon will lose mass, and the Ni(s) will be reduced.
The spoon will lose mass, and the Ni(s) will be oxidized.
The spoon will gain mass, and the Ni(s) will be reduced.
The spoon will gain mass, and the Ni(s) will be oxidized.
When the switch is closed, which electrode will attract the sodium ions?
Hint it's electrolytic reduction...see diagrams in outline, 14.4-5 notes and summary
The anode electrode
The cathode
Both electrodes
Neither electrode
What particles are provided by the electrolyte that allow an electric current to flow?
Electrons
Protons
Ions
Neutrons
Given the balanced equation representing a reaction occurring in an electrolytic cell: 2NaCl(ℓ) → 2Na(ℓ) + Cl₂(g) Where is Na(ℓ) produced in the cell?
at the anode, where oxidation occurs
at the anode, where reduction occurs
at the cathode, where oxidation occurs
at the cathode, where reduction occurs
The diagram here shows the electrolysis of fused KCl. What occurs when the switch is closed?
A. Positive metal ions migrate toward the anode, where they lose electrons.
B. Positive metal ions migrate toward the anode, where they gain electrons.
C. Positive metal ions migrate toward the cathode, where they lose electrons.
D. Positive metal ions migrate toward the cathode, where they gain electrons.
A metal object is to be electroplated with silver. Which set of electrodes should be used?
a silver anode and a metal object as the cathode
a platinum anode and a metal object as the cathode
a silver cathode and a metal object as the anode
a platinum cathode and a metal object as the anode
Which energy transformation occurs when an electrolytic cell is in operation?
chemical energy → electrical energy
electrical energy → chemical energy
light energy → heat energy
light energy → chemical energy
The diagram below shows a key being plated with copper in an electrolytic cell. Given the reduction reaction for this cell: Cu²⁺(aq) + 2e⁻ → Cu(s) This reduction occurs at
A, which is the anode
A, which is the cathode
B, which is the anode
B, which is the cathode
The purpose of the battery in this electrolytic cell is:
to provide energy for the non-spontaneous reaction
to act as the electrolyte
to supply ions to the solution
to collect the product gases
The diagram shown represents a chemical cell at 298 K. The equation below the diagram represents the net cell reaction. Use the diagram for the following problem(s). When switch S is closed, electrons in the external circuit will flow from
Al to Al³⁺
Al to Cu
Cu to Al
Cu to Cu²⁺
What occurs when the switch is closed?
Zn is reduced.
Cu is oxidized.
Electrons flow from Cu to Zn.
Electrons flow from Zn to Cu.
The direction of electron flow between the electrodes when switch S is closed is:
from the Pb (s) electrode to the wire to the Zn (s) electrode
from the Zn (s) electrode to the wire to the Pb (s) electrode
from the Pb (s) electrode to the salt bridge to the Zn (s) electrode
From the Zn (s) electrode to the salt bridge to the Pb (s) electrode
The mass of the Al(s) electrode decreases as the voltaic cell operates because, in terms of particles:
Al atoms lose electrons and enter the solution as Al3+ ions.
Al3+ ions gain electrons and deposit as Al atoms on the electrode.
Electrons are transferred from the solution to the Al electrode, increasing its mass.
Al atoms combine with oxygen from the air, forming Al2O3 on the electrode.
The mass of the copper electrode increases as the cell operates because:
Copper ions in solution gain electrons and are deposited as copper atoms on the electrode.
Copper atoms from the electrode lose electrons and become copper ions in solution.
Copper ions in solution lose electrons and form copper atoms in solution.
Copper atoms from the electrode gain electrons and become copper ions in solution.
Identify the anode in this cell.
Copper electrode
Zinc electrode
Silver electrode
Platinum electrode
Write a balanced half-reaction equation for the oxidation that occurs when the switch is closed.
Al(s) → Al3+(aq) + 3e−
Al3+(aq) + 3e− → Al(s)
Al(s) + 3e− → Al3+(aq)
Al3+(aq) → Al(s) + 3e−
In which substance is the oxidation number of nitrogen zero?
NH3
N2
NO2
N2O
What is the oxidation number of sulfur in H2SO4?
0
–2
+6
+4
The oxidation numbers of all the atoms in H2SO4 must add up to
0
+5
+9
+16
The oxidation number of hydrogen in sodium hydride (NaH) is
+1
+2
–1
–2
What are the two oxidation states of nitrogen in the compound NH4NO3?
–3 and –5
–3 and +5
+3 and –5
+3 and +5
In which compound does chlorine have the highest oxidation number?
NaClO
NaClO2
NaClO3
NaClO4
What is the oxidation state of nitrogen in NaNO2?
+1
+2
+3
+4
What is the oxidation number of carbon in H2CO3(aq)?
+4
+2
0
-4
Which half-reaction correctly represents reduction?
S2− + 2e− → S0
S2− + S0 → 2e−
Mn7+ + 3e− → Mn4+
Mn7+ → Mn4+ + 3e−
As an S2− ion is oxidized to an S0 atom, the number of protons in its nucleus
decreases
increases
remains the same
Given the reaction: Mg(s) + Cl2(g) → MgCl2(s) Which half-reaction correctly represents the reduction that occurs?
Mg(s) + 2e⁻ → Mg²⁺
Cl2(g) + 2e⁻ → 2Cl⁻
Mg²⁺ → Mg(s) + 2e⁻
2Cl⁻ → Cl2(g) + 2e⁻
Based on the given equation, write the balanced half-reaction that occurs in half-cell 1.
Pb(s) → Pb²⁺(aq) + 2e⁻
Pb²⁺(aq) + 2e⁻ → Pb(s)
Pb(s) + 2e⁻ → Pb²⁺(aq)
Pb²⁺(aq) → Pb(s) + 2e⁻
Given the reaction for the corrosion of aluminum: 4Al + 3O2 → 2Al2O3 Which half-reaction correctly represents the oxidation that occurs?
4Al + 12e⁻ → 4Al³⁺
4Al → 4Al³⁺ + 12e⁻
3O2 + 12e⁻ → 6O²⁻
2O2 → 2O²⁻ + 4e⁻
. What is conserved during a chemical reaction?
mass, only
neither mass nor charge
both mass and charge
charge, only
Which reaction occurs at the anode in an electrochemical cell?
saponification
oxidation
esterification
reduction
Which statement describes the two types of reactions that occur in operating electrochemical cells?
Nonspontaneous reactions occur in voltaic cells, and spontaneous reactions occur in electrolytic cells.
Nonspontaneous reactions occur in electrolytic cells, and nonspontaneous reactions occur in voltaic cells.
Spontaneous reactions occur in voltaic cells, and nonspontaneous reactions occur in electrolytic cells.
Spontaneous reactions occur in electrolytic cells, and spontaneous reactions occur in voltaic cells.
A collision between reactant particles is most likely to result in a reaction when the particles have proper orientation and proper
charge
energy
mass
radius
Which statement accurately describes particles of an ideal gas, according to the kinetic molecular theory?
The distance between the gas particles is much greater than the size of the particles
As the gas particles collide, the total energy of the system increases
The gas particles have strong intermolecular forces
The gas particles move in a circular motion
As the elements in Group 2 in the periodic table are considered in order of increasing atomic number, there is a general increase in
stability
atomic radius
electronegativity
first ionization energy
During the operation of a voltaic cell, the cell produces
electrical energy spontaneously
chemical energy spontaneously
electrical energy nonspontaneously
chemical energy nonspontaneously
Which statement explains why Group 18 elements are stable and unreactive?
They are all gases
They have low melting points.
Their valence electron shell has reached a full octet.
They have high ionization energies
In a redox reaction, which particles are lost and gained in equal numbers?
electrons
neutrons
hydroxide ions
hydronium ions
What is the oxidation state for a Mn atom?
0
+7
+3
+4
Which compounds are classified as electrolytes?
KNO₃ and H₂SO₄
KNO₃ and CH₃OH
CH₃OCH₃ and H₂SO₄
CH₃OCH₃ and CH₃OH
Which half-reaction correctly represents reduction?
Ag --> Ag+ + e-
F2 --> 2 F- + 2e-
Au3+ + 3e- --> Au
Fe2+ + e- --> Fe3+
In any redox reaction, the substance that undergoes reduction will
lose electrons and have a decrease in oxidation number
lose electrons and have an increase in oxidation number
gain electrons and have a decrease in oxidation number
gain electrons and have an increase in oxidation number
Sn(s) → Sn4+(aq) + 4e−
What is the oxidation number of carbon in NaHCO3?
What is oxidation number of Cr in Cr2O72-?
-2
+2
+6
+12
What is the oxidation state of H in H2?
+2
+1
0
None of the above
H in NaH ?
+1
0
-1
None of the above
Mg + PbCl2 --> MgCl2 + Pb. Which statement correctly describes the oxidation and reduction that occur?
Mg is oxidized and Cl- is reduced
Mg is oxidized and Pb+2 is reduced
Mg is reduced and Cl- is oxidized
Mg is reduced and Pb+2 is oxidized
Cl2 + 2e- --> 2Cl - is an example of:
a chemical reaction
redox
oxidation
reduction
4Fe + 3O2 --> 2Fe2O3
In the reaction Zn + H2O --> ZnO2 + H2
which element, if any, is oxidized?
Zn0
Zn+2
O-2
H20
None
What element is being reduced?
I0
H+1
S+4
O-2
What element is being Oxidized?
I0
H+1
S+4
O-2
The following chemical equation represents the extraction of silicon from quartz using coke.
SiO2 + C → Si + CO2
What is the change in oxidation number of silicon?
+2 to 0
+4 to 0
0 to +2
0 to +4
Mg → Mg2+ + 2e–
In the reaction Zn + 2HCl --> ZnCl2 + H2
which element, if any, is oxidized?
Zinc
Hydrogen
Chlorine
None
What is the oxidation number of oxygen in oxygen gas, O2 ?
-2
0
-1
+1
What is the oxidation number of C in SrCO3?
-4
+2
-6
+4
What is the oxidation number of chlorine in HClO?
Remember Chlorine goes a little crazy and can act out of character when it's with oxygen...
0
-1
+1
+5
Which energy conversion shown below takes place in a voltaic cell?
Electrical to chemical
Mechanical to chemical
Mechanical to electrical
Chemical to electrical
Which would be an accurate half-equation at the anode for aluminum?
Al3+ + 3e- --> Al
Al --> Al3+ + 3e-
Al3+ --> Al + 3e-
Al + 3e- --> Al3+
Which would be an accurate half-equation at the cathode for aluminum?
Al3+ + 3e- --> Al
Al --> Al3+ + 3e-
Al3+ --> Al + 3e-
Al + 3e- --> Al3+
Reduction occurs at the
anode
cathode
A diagram of a chemical cell and an equation are shown below.
Pb(s) + Cu2+(aq) → Pb2+(aq) + Cu(s)
When the switch is closed, electrons will flow from
the Pb(s) to the Cu(s)
the Cu(s) to the Pb(s)
the Pb2+(aq) to the Pb(s)
the Cu2+(aq) to the Cu(s)
Which statement identifies the part of the cell that conducts electrons and describes the direction of electron flow as the cell operates?
Remember who to consult when deciding who the anode is. Electrons are LOST at the anode therefore they must lave the anode; that's where they are produced (such as in oxidation half reactions)
Electrons flow through the salt bridge from the Ni(s) to the Zn(s).
Electrons flow through the salt bridge from the Zn(s) to the Ni(s).
Electrons flow through the wire from the Ni(s) to the Zn(s).
Electrons flow through the wire from the Zn(s) to the Ni(s).
Which statement correctly describes the direction of flow for the ions in this cell when the switch is closed?
Ions move through the salt bridge from B to C, only.
Ions move through the salt bridge from C to B, only.
Ions move through the salt bridge in both directions.
Ions do not move through the salt bridge in either direction.
When the switch is closed, which group of letters correctly represents the direction of electron flow?
A) A → B → C → D
B) A → F → E → D
C) D → C → B → A
D) D → F → E → A
Base your answer to the question on the diagram of the voltaic cell.
Based on the given equation, the balanced half-reaction that occurs in half-cell 1 is
Pb(s) → Pb2+(aq) + 2e-
2Ag(s) → 2Ag+(aq) + 2e-
Pb2+(aq) + 2e- → Pb(s)
2Ag+(aq) + 2e- → Ag(s)
What is the role of the salt bridge in a voltaic cell? (Check all that apply)
To allow the movement of water molecules between the two half cells
To allow the movement of electrons between the half cells
To allow the movement of ions to maintain charge neutrality
Consider the diagram of a voltaic cell represented here. What reaction occurs at the anode?
Chem is CONSTANT analysis! As pointed out in class, please make sure you are evaluating what is in front of you and not assuming i.e., which side left orright is which anode.
Ag+ + e- →Ag
Ag → Ag+ + e-
Ni2+ + 2e- → Ni
Ni → Ni2+ + 2e-
A power source is required for this cell to operate because the REDOX reaction is:
nonspontaneous and converts electrical energy to chemical energy
spontaneous and converts electrical energy to chemical energy
nonspontaneous and converts chemical energy to electrical energy
spontaneous and converts chemical energy to electrical energy
In the electrochemical cell shown, the Ni(s) is the:
anode and increases in mass as the cell operates
anode and decreases in mass as the cell operates
cathode and increases in mass as the cell operates
cathode and decreases in mass as the cell operates
The purpose of the salt bridge is to allow (a) to flow to maintain neutrality as the cell operates.
This diagram represents:
a voltaic cell that converts chemical energy to electrical energy
an electrolytic cell that converts chemical energy to electrical energy
a voltaic cell that converts electrical energy to chemical energy
a electrolytic cell that converts electrical energy to chemical energy
According to reference Table J, which of the following reactions would occur spontaneously?
A
B
C
D
Which of the following half reactions represents reduction?
a
b
c
d
Which of the following half reactions represents oxidation?
a
b
c
d
Which species has been oxidized in the reaction shown?
Co(s)
Cu+1(aq)
Cu(s)
Co+3(aq)
In the REDOX reaction shown, silver (Ag) has:
lost electrons resulting in oxidation
gained electrons resulting in oxidation
lost electrons resulting in reduction
gained electrons resulting in reduction
All REDOX reactions are examples of _______ transfer reactions.
neutron
ion
electron
proton
A key is plated with nickel as shown in the diagram below.
A) voltaic cell; a chemical change produces electrical energy
B) electrolytic cell; a chemical change produces electrical energy
C) voltaic cell; electrical energy produces a chemical change
D) electrolytic cell; electrical energy produces a chemical change
Based on Table J, which ionic equation represents a spontaneous reaction that can occur in a voltaic cell?
A) Fe(s) + Mg²⁺(aq) → Fe²⁺(aq) + Mg(s)
B) Fe²⁺(aq) + Mg²⁺(aq) → Fe(s) + Mg(s)
C) Fe(s) + Mg(s) → Fe²⁺(aq) + Mg²⁺(aq)
D) Fe²⁺(aq) + Mg(s) → Fe(s) + Mg²⁺(aq)
In which kind of cell are the redox reactions made to occur by an externally applied electrical current?
galvanic cell
chemical cell
voltaic cell
electrolytic cell
The diagram shows a key being plated with copper in an electrolytic cell. Given the reduction reaction for this cell:
Cu²⁺(aq) + 2e⁻ → Cu(s)
this reduction occurs at
A, which is the anode
A, which is the cathode
B, which is the anode
B, which is the cathode
Write the balanced half-reaction for the reduction that occurs in this electrolytic cell.
This is an electrolytic (reduction). These special cells have the negative ion serving as the anode (getting oxidized)...
Cl2 + 2e⁻ → 2Cl⁻
Cl2 → 2Cl⁻ + 2e⁻
2Na⁺ + 2e⁻ → 2Na
2Na⁺ → 2Na + 2e⁻
Refer to diagram
Solutions, such as solution X, are always used in electrochemical cells.
What is the general term used to describe these solutions.
Electrolyte
Electrons
Photons
What is happening at the Fe electrode/Half Cell 2
Not sure which electrode is the cathode or anode - consult table j!
Fe atoms are being reduced to Fe+2 ions
Fe+2 ions are being oxidized to Fe atoms
Fe+2 ions are being reduced to Fe atoms
Fe atoms are being oxidized to Fe+2 ions
What occurs to the mass of copper electrode in the following reaction?
Zn/Zn2+ // Cu2+/Cu
Don't know which anode is which - who you gonna call?
increases
decreases
remains the same
The electrode that contains the item to be electroplated
Anode
Cathode
Which type of substance will conduct
electricity the best after dissolving in water?
metallic
ionic
network covalent
molecular covalent
The energy change in voltaic cell is ______________.
kinetic energy --> electrical energy
electrical energy --> chemical energy
chemical energy --> electrical energy
electrical energy --> kinetic energy
Write the balanced half-reaction for the reduction that occurs in this electrolytic cell.
Cl2 + 2e⁻ → 2Cl⁻
Cl2 → 2Cl⁻ + 2e⁻
2Na⁺ + 2e⁻ → 2Na
2Na⁺ → 2Na + 2e⁻
What type of electrochemical cell is shown?
oxidation cell
electrolytic cell
reduction cell
voltaic cell
In this electrolytic cell, electrode A is designated as the
anode and is positive
anode and is negative
cathode and is positive
cathode and is negative
Which type of cell does the diagram represent?
electrolytic, with the anode at A
electrolytic, with the cathode at A
voltaic, with the anode at A
voltaic, with the cathode at A
As the pH of a solution is changed from 3 to 1, the concentration of hydronium ions
decreases by a factor of 100
decreases by a factor of 20
increases by a factor of 20
increases by a factor of 100
As the pH of a solution changes from 2 to 5, the concentration of hydronium ions
decreases by a factor of 30
decreases by a factor of 1000
increases by a factor of 1000
increases by a factor of 30
Which relationship is present in a solution that has a pH of 6?
[H3O+] = [OH-]
[H3O+] > [OH-]
[H3O+] < [OH-]
[H3O+] + [OH-] = 7
Given the equation representing a reaction:
3CuCl2(aq) + 2Al(s) --> 3Cu(s) + 2AlCl3(aq)
The oxidation number of copper changes from
+1 to 0
+2 to 0
+2 to +1
+6 to +3
1
2
3
4
7. Electroplating is an electrolytic process that can be used to coat metal objects with a less reactive metal. The diagram below shows an electroplating cell that includes a power source connected to a copper rod and a bracelet made from a different metal. The rod and bracelet are in an aqueous copper(II) sulfate solution.
Identify the electrode that attracts the Cu2+ ions as the cell operates.
(a)
8. Electroplating is an electrolytic process that can be used to coat metal objects with a less reactive metal. The diagram below shows an electroplating cell that includes a power source connected to a copper rod and a bracelet made from a different metal. The rod and bracelet are in an aqueous copper(II) sulfate solution.
Write a balanced half reaction equation for the REDUCTION of Cu2+ that occurs in this cell.
(a)
The diagram and ionic equation below represent an operating voltaic cell:
1. from Ni(s) through the wire to Mg(s)
2. from Mg(s) through the wire to Ni(s)
3. from Ni2+(aq) ions through the salt bridge to Mg2+(aq) ions
4. from Mg2+(aq) ions through the salt bridge to Ni2+(aq) ions
Which ionic equation represents a spontaneous reaction that can occur in a voltaic cell?
Cu(s) + Zn(s) Cu2+(aq) + Zn2+(aq)
Cu(s) + Zn2+(aq) Cu2+(aq) + Zn(s)
Cu2+(aq) + Zn(s) Cu(s) + Zn2+(aq)
Cu2+(aq) + Zn2+(aq) Cu(s) + Zn(s)
Based on Reference Table F, which of these salts is the best electrolyte?
sodium nitrate
magnesium carbonate
silver chloride
barium sulfate
Which is a redox reaction?
HCl + KOH KCl + H2O
4 HCl + MnO2 MnCl2 + 2 H2O + Cl2
2 HCl +CaCO3 CaCl2 + H2O + CO2
2 HCl + FeS FeCl2 + H2S
Given the balanced ionic equation representing a reaction:
2 Al3+(aq) + 3 Mg(s) 3 Mg2+(aq) + 2 Al(s)
In this reaction, electrons are transferred from
Al to Mg2+
Al3+ to Mg
Mg to Al3+
Mg2+ to Al
Which process is represented by this diagram?
chromatography
distillation
electrolysis
polymerization
Which process requires energy to decompose a substance?
electrolysis
neutralization
sublimation
synthesis
Given the balanced equation representing a reaction: Ni(s) + 2HCl(aq) → NiCl₂(aq) + H₂(g). In this reaction, each Ni atom
loses 1 electron
loses 2 electrons
gains 1 electron
gains 2 electrons
According to Reference Table F, which compound is most soluble in water?
BaCO3
BaSO4
ZnCO3
ZnSO4
Identify the electrode that attracts the Cu2+ ions as the cell operates.
The bracelet (cathode) attracts the Cu2+ ions.
The anode attracts the Cu2+ ions.
The salt bridge attracts the Cu2+ ions.
The electrolyte attracts the Cu2+ ions.
Write a balanced half-reaction equation for the reduction of Cu2+ ions that occurs in this cell.
Cu2+ + 2e- → Cu(s)
Cu(s) → Cu2+ + 2e-
Cu2+ → Cu(s) + 2e-
Cu(s) + 2e- → Cu2+
