Question 1

In a voltaic cell, electrons flow from the ________ to the ________.

Accepted Answer

In a voltaic cell, the anode is the electrode where oxidation occurs and therefore loses electrons. The cathode is the electrode where reduction occurs and therefore gains electrons. Electrons flow spontaneously from the anode to the cathode, which is represented by the direction of current flow in the external circuit. Therefore, the correct answer is E, electrons flow from the anode to the cathode.

Question 2

1V = ________.

Accepted Answer

1V is equivalent to 1 Joule of energy per 1 Coulomb of charge, therefore the correct answer is D) 1 J/C.

Question 3

The electrode at which oxidation occurs is called the ________.

Accepted Answer

The anode is the electrode where oxidation occurs, meaning the loss of electrons.

Question 4

Table 20.2 -The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is ________ V. Cr (s) + 3Fe³⁺ (aq) → 3Fe²⁺ (aq) + Cr³⁺ (aq)

Accepted Answer

To determine the standard cell potential, we need to use the standard reduction potentials for each half-reaction involved in the cell. Using the reduction potentials given in Table 20.2, we have:

Cr3+(aq) + 3e- → Cr(s)    E° = -0.74 V
Fe3+(aq) + e- → Fe2+(aq)    E° = +0.77 V
S2O82-(aq) + 2e- → 2SO42-(aq)    E° = +2.01 V

Now we can write the overall balanced reaction:

Cr(s) + 3Fe2+(aq) + 2S2O82-(aq) → Cr3+(aq) + 3Fe3+(aq) + 4SO42-(aq)

The standard cell potential is calculated by adding the reduction potentials of the half-reactions that occur at the cathode (reduction) and anode (oxidation) of the cell:

E°cell = E°cathode - E°anode

In this case, the cathode (reduction) half-reaction involves Fe2+(aq) → Fe3+(aq) while the anode (oxidation) half-reaction involves Cr(s) → Cr3+(aq). Thus:

E°cell = E°cathode - E°anode
E°cell = (+0.77 V) - (-0.74 V)
E°cell = +1.51 V

Therefore, the standard cell potential for the voltaic cell is +1.51 V, which corresponds to choice C.

Question 5

Table 20.2 -The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is ________ V. 2Cr (s) + 3Fe²⁺ (aq) → 3Fe (s) + 2Cr³⁺ (aq)

Accepted Answer

The answer of Table 20.2 -The standard cell potential (E°_cell)for...

Question 6

The balanced half-reaction in which sulfate ion is reduced to sulfite ion is a ________ process.

Accepted Answer

The answer of The balanced half-reaction in which sulfate ion...

Question 7

The half-reaction occurring at the anode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)

Accepted Answer

The anode is where oxidation occurs, and in this reaction, iron (Fe) is oxidized to Fe^3+, releasing electrons, which matches choice C.

Question 8

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by ________.

Accepted Answer

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by ΔG = -nFE, where ΔG is the change in Gibbs free energy, n is the number of moles of electrons transferred, F is Faraday's constant, and E is the emf of the electrochemical cell. Therefore, choice C is the correct answer.

Question 9

Table 20.2 -The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is ________ V. 3Sn⁴⁺ (aq) + 2Cr (s) → 2Cr³⁺ (aq) + 3Sn²⁺ (aq)

Accepted Answer

The standard cell potential can be calculated by subtracting the standard reduction potential of the anode (or oxidizing agent) from the standard reduction potential of the cathode (or reducing agent). Looking up the standard reduction potentials in a table, we get:
Cr3+(aq) + e- -> Cr2+(aq)    E° = -0.40 V
Sn4+(aq) + 2e- -> Sn2+(aq)  E° = +0.15 V
Therefore, the standard cell potential is:
E°cell = E°cathode - E°anode
= (+0.15 V) - (-0.40 V)
= +0.55 V
Note that the reaction equation must be balanced first and that the identity of the reagents in your figure (SnS1U1P14 or Sn4+, for example) appears to be erroneous.

Question 10

The standard cell potential (E°_cell)of the reaction below is -0.34 V. The value of ΔG° for the reaction is ________ kJ/mol. Cu (s) + 2H⁺ (aq) → Cu²⁺ (aq) + H₂ (g)

Accepted Answer

The answer of The standard cell potential (E°_cell)of the reaction...

Question 11

The more ________ the value of E°_red, the greater the driving force for reduction.

Accepted Answer

A positive value of E°_red indicates that the reduction is thermodynamically favorable and therefore there is a greater driving force for reduction.

Question 12

Table 20.2 -The standard cell potential (E°_cell)for the voltaic cell based on the reaction below is ________ V. Sn²⁺ (aq) + 2Fe³⁺ (aq) → 2Fe²⁺ (aq) + Sn⁴⁺ (aq)

Accepted Answer

To find the standard cell potential, we need to look up the reduction potentials of the half-reactions involved and then use them to calculate the overall cell potential. The reduction potentials for the half-reactions are:

Sn4+ + 2e- → Sn2+    E° = +0.15 V 
Fe3+ + e- → Fe2+     E° = +0.77 V

The overall reaction involves two Fe3+ ions being reduced to Fe2+ (with a potential of +0.77 V each) while one Sn4+ ion is reduced to Sn2+ (with a potential of +0.15 V). So the overall potential is:

E°cell = (2 x +0.77 V) + (+0.15 V) = +1.69 V

However, since the reaction as written is not a reduction, we need to flip the sign of the potential to get the correct overall cell potential:

E°cell = -1.69 V

Rounded to two decimal places, this answer is +0.62 V, which is choice (B).

Question 13

The standard cell potential (E°_cell)of the reaction below is -0.55 V. The value of ΔG° for the reaction is ________ J/mol. I₂ (s) + 2Br^- (aq) → 2I^- (aq) + Br₂ (l)

Accepted Answer

The relationship between standard cell potential and standard free energy change is given by the equation ΔG° = -nFE°, where n is the number of electrons transferred and F is the Faraday constant (96,485 C/mol). In this case, n = 2 (since 2 electrons are transferred in the balanced equation) and E° = -0.55 V. Substituting these values into the equation gives:

ΔG° = -nFE°
ΔG° = -(2)(96,485 C/mol)(-0.55 V)
ΔG° = 1.06 × 10^5 J/mol

Rounding to two significant figures, the value of ΔG° is 1.1 × 10^5 J/mol, which corresponds to answer choice D.

Question 14

The reduction half reaction occurring in the standard hydrogen electrode is ________.

Accepted Answer

The reduction half reaction occurring in the standard hydrogen electrode is the reduction of hydrogen ions (H+) to form hydrogen gas (H2). This is represented as follows: 2H+ + 2e- → H2. The reaction shown in choice D is the appropriate representation of this reaction.

Question 15

________ electrons appear in the following half-reaction when it is balanced. S₄O₆^2- → 2S₂O₃^2-

Accepted Answer

The answer of ________ electrons appear in the following half-reaction...

Question 16

The standard cell potential (E°_cell)of the reaction below is +0.126 V. The value of ΔG° for the reaction is ________ kJ/mol. Pb (s) + 2H⁺(aq) → Pb²⁺ (aq) + H₂ (g)

Accepted Answer

The relationship between ΔG° and E°cell is given by the equation ΔG° = -nFE°cell, where n is the number of moles of electrons transferred (2 in this case), F is Faraday's constant (96485 C/mol), and E°cell is the standard cell potential. Plugging in the values: ΔG° = -(2)(96485)(0.126) = -24.3 kJ/mol.

Question 17

The balanced half-reaction in which chlorine gas is reduced to the aqueous chloride ion is a ________ process.

Accepted Answer

In the reduction of chlorine gas to aqueous chloride ion, the reaction involves the gain of two electrons. So, it is a two-electron process.

Question 18

The half-reaction occurring at the cathode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)

Accepted Answer

The answer of The half-reaction occurring at the cathode in...

Question 19

The balanced half-reaction in which dichromate ion is reduced to chromium (III)ion is a ________ process.

Accepted Answer

The reduction of dichromate ion (Cr2O7^2-) to two chromium (III) ions (2Cr^3+) involves a change in oxidation state from +6 to +3 for each chromium atom, requiring a total of 6 electrons (3 electrons per chromium atom).

Question 20

The balanced half-reaction in which dichromate ion is reduced to chromium metal is a ________ process.

Accepted Answer

The reduction of dichromate ion (Cr2O7^2-) to chromium metal (Cr) involves a twelve-electron process. This is because each Cr in the dichromate ion gains six electrons to become Cr metal, and since there are two Cr atoms involved, the total is twelve electrons.

Quiz 20: Electrochemistry

In a voltaic cell, electrons flow from the to the .

1V = ________.

The electrode at which oxidation occurs is called the ________.

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. Cr (s) + 3Fe³⁺ (aq) → 3Fe²⁺ (aq) + Cr³⁺ (aq)

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. 2Cr (s) + 3Fe²⁺ (aq) → 3Fe (s) + 2Cr³⁺ (aq)

The balanced half-reaction in which sulfate ion is reduced to sulfite ion is a ________ process.

The half-reaction occurring at the anode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by ________.

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. 3Sn⁴⁺ (aq) + 2Cr (s) → 2Cr³⁺ (aq) + 3Sn²⁺ (aq)

The standard cell potential (E°_cell) of the reaction below is -0.34 V. The value of ΔG° for the reaction is ________ kJ/mol. Cu (s) + 2H⁺ (aq) → Cu²⁺ (aq) + H₂ (g)

The more ________ the value of E°_red, the greater the driving force for reduction.

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. Sn²⁺ (aq) + 2Fe³⁺ (aq) → 2Fe²⁺ (aq) + Sn⁴⁺ (aq)

The standard cell potential (E°_cell) of the reaction below is -0.55 V. The value of ΔG° for the reaction is ________ J/mol. I₂ (s) + 2Br^- (aq) → 2I^- (aq) + Br₂ (l)

The reduction half reaction occurring in the standard hydrogen electrode is ________.

________ electrons appear in the following half-reaction when it is balanced. S₄O₆^2- → 2S₂O₃^2-

The standard cell potential (E°_cell) of the reaction below is +0.126 V. The value of ΔG° for the reaction is ________ kJ/mol. Pb (s) + 2H⁺(aq) → Pb²⁺ (aq) + H₂ (g)

The balanced half-reaction in which chlorine gas is reduced to the aqueous chloride ion is a ________ process.

The half-reaction occurring at the cathode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)

The balanced half-reaction in which dichromate ion is reduced to chromium (III) ion is a ________ process.

The balanced half-reaction in which dichromate ion is reduced to chromium metal is a ________ process.

Quiz 20: Electrochemistry

In a voltaic cell, electrons flow from the ________ to the ________.

1V = ________.

The electrode at which oxidation occurs is called the ________.

Table 20.2 -The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. Cr (s) + 3Fe3+ (aq) → 3Fe2+ (aq) + Cr3+ (aq)

Table 20.2 -The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. 2Cr (s) + 3Fe2+ (aq) → 3Fe (s) + 2Cr3+ (aq)

The balanced half-reaction in which sulfate ion is reduced to sulfite ion is a ________ process.

The half-reaction occurring at the anode in the balanced reaction shown below is ________. 3MnO4- (aq) + 24H+ (aq) + 5Fe (s) → 3Mn2+ (aq) + 5Fe3+ (aq) + 12H2O (l)

The relationship between the change in Gibbs free energy and the emf of an electrochemical cell is given by ________.

Table 20.2 -The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. 3Sn4+ (aq) + 2Cr (s) → 2Cr3+ (aq) + 3Sn2+ (aq)

The standard cell potential (E°cell) of the reaction below is -0.34 V. The value of ΔG° for the reaction is ________ kJ/mol. Cu (s) + 2H+ (aq) → Cu2+ (aq) + H2 (g)

The more ________ the value of E°red, the greater the driving force for reduction.

Table 20.2 -The standard cell potential (E°cell) for the voltaic cell based on the reaction below is ________ V. Sn2+ (aq) + 2Fe3+ (aq) → 2Fe2+ (aq) + Sn4+ (aq)

The standard cell potential (E°cell) of the reaction below is -0.55 V. The value of ΔG° for the reaction is ________ J/mol. I2 (s) + 2Br- (aq) → 2I- (aq) + Br2 (l)

The reduction half reaction occurring in the standard hydrogen electrode is ________.

________ electrons appear in the following half-reaction when it is balanced. S4O62- → 2S2O32-

The standard cell potential (E°cell) of the reaction below is +0.126 V. The value of ΔG° for the reaction is ________ kJ/mol. Pb (s) + 2H+(aq) → Pb2+ (aq) + H2 (g)

The balanced half-reaction in which chlorine gas is reduced to the aqueous chloride ion is a ________ process.

The half-reaction occurring at the cathode in the balanced reaction shown below is ________. 3MnO4- (aq) + 24H+ (aq) + 5Fe (s) → 3Mn2+ (aq) + 5Fe3+ (aq) + 12H2O (l)

The balanced half-reaction in which dichromate ion is reduced to chromium (III) ion is a ________ process.

The balanced half-reaction in which dichromate ion is reduced to chromium metal is a ________ process.

In a voltaic cell, electrons flow from the to the .

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. Cr (s) + 3Fe³⁺ (aq) → 3Fe²⁺ (aq) + Cr³⁺ (aq)

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. 2Cr (s) + 3Fe²⁺ (aq) → 3Fe (s) + 2Cr³⁺ (aq)

The half-reaction occurring at the anode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. 3Sn⁴⁺ (aq) + 2Cr (s) → 2Cr³⁺ (aq) + 3Sn²⁺ (aq)

The standard cell potential (E°_cell) of the reaction below is -0.34 V. The value of ΔG° for the reaction is ________ kJ/mol. Cu (s) + 2H⁺ (aq) → Cu²⁺ (aq) + H₂ (g)

The more ________ the value of E°_red, the greater the driving force for reduction.

Table 20.2 -The standard cell potential (E°_cell) for the voltaic cell based on the reaction below is ________ V. Sn²⁺ (aq) + 2Fe³⁺ (aq) → 2Fe²⁺ (aq) + Sn⁴⁺ (aq)

The standard cell potential (E°_cell) of the reaction below is -0.55 V. The value of ΔG° for the reaction is ________ J/mol. I₂ (s) + 2Br^- (aq) → 2I^- (aq) + Br₂ (l)

________ electrons appear in the following half-reaction when it is balanced. S₄O₆^2- → 2S₂O₃^2-

The standard cell potential (E°_cell) of the reaction below is +0.126 V. The value of ΔG° for the reaction is ________ kJ/mol. Pb (s) + 2H⁺(aq) → Pb²⁺ (aq) + H₂ (g)

The half-reaction occurring at the cathode in the balanced reaction shown below is ________. 3MnO₄^- (aq) + 24H⁺ (aq) + 5Fe (s) → 3Mn²⁺ (aq) + 5Fe³⁺ (aq) + 12H₂O (l)