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WorksheetsQuiz 3: Electrochemistry
Total questions: 53
Worksheet time: 3hrs 33mins
An oxidizing agent will
increase in mass
lose electrons
be reduced
increase in oxidation number
In a redox reaction, the species that loses electrons
is called the cathode
is oxidized
gains mass at the electrode
decreases in oxidation number
As an element is oxidized, its oxidation number
decreases as electrons are lost
increases as electrons are lost
decreases as electrons are gained
increases as electrons are gained
Oxidation-reduction reactions occur because of the competition between particles for
electrons
positrons
protons
neutrons
Mg + PbCl2 → MgCl2 + Pb
Which statement correctly describes the oxidation and reduction that occur?
Mg is oxidized and Pb2+ is reduced
Mg is oxidized and Cl- is reduced
Mg is reduced and Cl- is oxidized
Mg is reduced and Pb2+ is oxidized
In the reactions
Sn2+(aq) + 2Fe3+(aq) -> Sn4+(aq) + 2Fe2+(aq),
the reducing agent is
Fe3+
Sn2+
Sn4+
Fe2+
Pb(s) + 2Ag+(aq)→ Pb2+(aq) + 2Ag(s)
The chemical species being reduced is
Ag
Pb
Pb2+
Ag+
If acidified potassium dichromate(VI) (K2Cr2O7) acts as oxidizing agent, color changes from
orange to red
orange to green
yellow to green
yellow to red
In electrolysis of copper purification, at cathode
pure copper gets deposited
the object to be electroplated is kept
impure copper gets deposited
CuSO4 gets deposited
An electrolytic cell uses electrical energy to drive
chemical reaction
physical reaction
no reaction
none of above
Galvanic cells convert
mechanical energy in to electrical energy
potential energy in to electrical energy
electrical energy in to chemical energy
chemical energy in to electrical energy
When water is electrolyzed, gas collected at cathode, is
sulphur
oxygen
hydrogen
sulphur dioxide
In electrolysis, particles which move towards cathode are called
anions
cations
photons
positrons
Electrons always flow from
cathode to anode
anode to cathode
Oxidation occurs at the
anode
cathode
Electrons are gained at the
anode
cathode
Given their standard reduction potentials, which of the species is going to be oxidized?
Cu2+/Cu = +0.34V
Zn2+/Zn = -0.76V
Cu
Zn
CuSO4
ZnSO4
What occurs to the mass of copper electrode in the following reaction?
Zn(s)/Zn2+(aq) // Cu2+(aq)/Cu(s)
increases
decreases
remains the same
What is reduction?
It is the gain of electrons.
It is the loss of electrons.
It is the creation of electrons.
It is the destruction of electrons.
What is oxidation?
It is the gain of electrons.
It is the loss of electrons.
It is the creation of electrons.
It is the destruction of electrons.
What is a reducing agent?
It is the species that gets reduced -- gains electrons.
It is the species that gets oxidized -- loses electrons.
It is the species that creates electrons.
It is the species that destroys electrons.
What is an oxidizing agent?
It is the species that gets reduced -- gains electrons.
It is the species that gets oxidized -- loses electrons.
It is the species that creates electrons.
It is the species that loses electrons.
What is a standard half-cell?
It is one cell that comprises half of a whole battery.
It is a cell containing only a metal bar with no aqueous ion solution.
It is a cell containing only an aqueous ion solution and no metal bar.
It is a cell that generates half of a volt of electricity.
What is a galvanic (voltaic) cell?
It is a cell that destroys electrons on one side and creates electrons on the other side.
It is a cell that contains only one metal bar and one aqueous ion solution.
It is a type of battery that drives a redox reaction when electricity is applied.
It is a type of battery that generates an electrical current from redox reactions.
What is a half-reaction?
It is a reaction at equilibrium where half of the substances are reactants and half of the substances are products.
It is the reaction that occurs when the switch of a galvanic cell is open.
It shows EITHER the reduction component or the oxidation component of a redox reaction.
It shows BOTH the reduction and oxidation components of a redox reaction.
What is an anode?
It is the electrode where oxidation takes place.
It is the electrode where reduction takes place.
It is an aqueous solution containing an electrode.
It is the salt bridge that connects half-cells.
What is a cathode?
It is the electrode where oxidation takes place.
It is the electrode where reduction takes place.
It is an aqueous solution containing an electrode.
It is the salt bridge that connects half-cells.
Electrochemistry is
Study of electron in atom
Study of electricity in molecules
The relationship between chemical reactions and electricity
the study of electrons moving from one a tom to another
Given the standard electrode potentials,
K+/K = −2.93V, Ag+/Ag =+0.80V,
Hg2+/Hg =+0.79V
Mg2+/Mg = −2.37 V, Cr3+/Cr = − 0.74V
their increasing order as reducing agent.
K<Mg<Cr<Hg<Ag
Ag >Hg > Cr > Mg > K
Ag < Hg < Cr < Mg < K
K>Mg>Cr>Hg>Ag
Nernst equation FOR (i) Mg(s) | Mg2+(aq,0.001M) || Al3+(aq,0.0001 M) | Al(s)
Ecell=E0cell-0.0591/6 log[Mg2+]3/[Al3+]2
Ecell=E0cell-0.0591/6 log[Al3+]2/[Mg2+]3
Ecell=E0cell+0.0591/3 log[Mg2+]3/[Al3+]2
Ecell=E0cell-0.0591/3 log[Mg2+] /[Al3+]
How much charge in Faraday is required for the following reductions:
1 mol of Al3+ to Al.
1F
2F
3F
4F
How would you write the electrons in the reaction O2 --> O22-?
+2e- on the products
+2e- on the reactants
+e- on the products
+e- on the reactants
Which statement best describes how a salt bridge maintains electrical neutrality in the half-cells of an electrochemical cell?
It prevents the migration of electrons.
It prevents the reaction from occurring spontaneously.
It permits the migration of ions.
It allows for the reaction from occurring spontaneously.
When an electrochemical cell is operating, it is
approaching equilibrium
using external energy
undergoing oxidation, only
undergoing reduction, only
Fe2+ + 2e– → Fe(s) E° = –0.44 volt
Ni2+ + 2e– → Ni(s) E° = –0.23 volt
The standard reduction potentials for two half reactions are given above. The Nernst equation for a galvanic cell at 25°C in which Fe(s) reduces Ni2+ is the following.
E = E° – 0.03 log [Fe2+]/[Ni2+]
What is the equilibrium constant for the reaction below?
Fe(s) + Ni2+ → Fe2+ + Ni(s)
1.9 × 10–23
7.6 × 10–8
3.6 × 103
1.3 × 107
In electrolysis of 0.001 mol/dm3 aqueous NaCl solution, which ion will be selectively discharged at the anode?
Na+ ions
Cl- ions
OH- ions
H+ ions
The net products that result from the electrolysis of water are?
H2 and OH-
O2 and H-
H+ and OH-
H2 and O2
Calculate the standard cell potential.
Ni(s) + 2Fe3+(aq) ----> Ni2+ (aq)+ Fe2+(aq)
1.02 V
-1.02 V
-0.19 V
-0.286 V
What occurs to the mass of copper electrode in the following reaction?
Zn(s)/Zn2+(aq) // Cu2+(aq)/Cu(s)
increases
decreases
remains the same
If Al is above Co in the activity series of metals, which of the following will occur if Al metal is put into a solution of cobalt nitrate?
a redox reaction takes place
the Al strip dissolves
the Al strip becomes coated with cobalt
all of the above
The covering of a thin layer of metal is
electrowinning
electrorefining
electroplating
electromachining
