Question 1

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

Accepted Answer

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

Question 2

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

Accepted Answer

Electrons flow from the anode (where oxidation occurs and electrons are lost) to the cathode (where reduction occurs and electrons are gained) in a voltaic cell. The salt bridge is used to maintain charge neutrality by allowing ions to flow between the two half-cells, but it does not directly participate in the electron flow.

Question 3

What is the oxidation number of manganese in MnO₂?

Accepted Answer

The oxidation number of oxygen is usually -2 and sulfur is usually -2 or -1. The sum of oxidation numbers in a compound equals zero. Let x be the oxidation number of manganese. Then we can write the equation: x + (-2) + (-2) = 0 Solving for x, we get x = +4. Therefore, the oxidation number of manganese in MnO₂ is +4, which is option D.

Question 4

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 5

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

The standard cell potential is calculated using the standard reduction potentials of the half-reactions. The reduction potential for Sn⁴⁺/Sn²⁺ is -0.15 V and for Fe³⁺/Fe²⁺ is +0.77 V. The cell potential is the difference: E°_cell = 0.77 V - (-0.15 V) = +0.617 V.

Question 6

1V = __________.

Accepted Answer

1V = 1 J/C (by definition)

Question 7

What is the oxidation number of chromium in Cr₂O ion?

Accepted Answer

The answer of What is the oxidation number of chromium...

Question 8

What is the oxidation number of manganese in the MnO  ion?

Accepted Answer

The answer of What is the oxidation number of manganese...

Question 9

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

Accepted Answer

A positive value of E° indicates that the reaction is spontaneous and has a greater driving force for reduction. A negative value of E° would indicate that the reaction is not spontaneous and would require an external source of energy to occur.

Question 10

What is the oxidation number of oxygen in H₂O₂?

Accepted Answer

The answer of What is the oxidation number of oxygen...

Question 11

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

Accepted Answer

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

Question 12

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 13

What is the oxidation number of potassium in KMnO₄?

Accepted Answer

The oxidation state of the other elements present in the compound can be calculated as follows: 
- The oxidation state of Mn in KMnO4 is +7 (since oxygen has an oxidation state of -2 and there are four of them, their total oxidation state is -8; the oxidation state of potassium is +1, so the oxidation state of Mn can be calculated as: (+1) + Mn + (-8) = 0; solving for Mn gives +7).
- The oxidation state of oxygen in KMnO4 is -2.
- The oxidation state of sulfur is -2.
- Therefore, the oxidation state of potassium can be calculated as (+1) + Mn + (-2) + (-2) + (-1) + (-1) + (-1) + (-1) + (-1) + (-1) = 0, which gives a value of +1 for potassium.

Question 14

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 cathode half-reaction involves the reduction of MnO₄⁻ to Mn²⁺, which is shown in choice A.

Question 15

The electrode at which oxidation occurs is called the __________.

Accepted Answer

According to electrochemical conventions, oxidation occurs at the anode.

Question 16

Which substance is the reducing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

Accepted Answer

In the reaction, lead (Pb) is being oxidized from a 0 to +2 oxidation state, while the lead oxide (PbO) is being reduced from a +2 to 0 oxidation state. Therefore, Pb is the reducing agent, as it is causing the reduction of PbO.

Question 17

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

Accepted Answer

The reduction half reaction occurring in the standard hydrogen electrode is 2H+ (aq) + 2e- -> H2 (g). This is equivalent to choice D. The other choices are not related to the reduction half reaction occurring in the standard hydrogen electrode.

Question 18

Which substance is the oxidizing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

Accepted Answer

In the reaction, lead oxide (PbO) is being reduced to lead (Pb) and therefore is the substance being oxidized. The substance that causes the oxidation is the oxidizing agent, which is H₂SO₄. Therefore, the correct choice is C, PbO₂.

Question 19

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

Accepted Answer

The balanced half-reaction for the reduction of chlorine gas to the aqueous chloride ion is:

Cl2 + 2e- → 2Cl-

This involves the transfer of two electrons, making it a two-electron process.

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

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

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

What is the oxidation number of manganese in MnO₂?

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

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)

1V = __________.

What is the oxidation number of chromium in Cr₂O ion?

What is the oxidation number of manganese in the MnO ion?

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

What is the oxidation number of oxygen in H₂O₂?

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

What is the oxidation number of potassium in KMnO₄?

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 electrode at which oxidation occurs is called the __________.

Which substance is the reducing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

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

Which substance is the oxidizing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

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

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

Quiz 20: Electrochemistry

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

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

What is the oxidation number of manganese in MnO2?

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

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)

1V = __________.

What is the oxidation number of chromium in Cr2O ion?

What is the oxidation number of manganese in the MnO ion?

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

What is the oxidation number of oxygen in H2O2?

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

What is the oxidation number of potassium in KMnO4?

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 electrode at which oxidation occurs is called the __________.

Which substance is the reducing agent in the reaction below? Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O

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

Which substance is the oxidizing agent in the reaction below? Pb + PbO2 + 2H2SO4 → 2PbSO4 + 2H2O

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

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

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

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

What is the oxidation number of manganese in MnO₂?

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)

What is the oxidation number of chromium in Cr₂O ion?

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

What is the oxidation number of oxygen in H₂O₂?

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)

What is the oxidation number of potassium in KMnO₄?

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)

Which substance is the reducing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O

Which substance is the oxidizing agent in the reaction below? Pb + PbO₂ + 2H₂SO₄ → 2PbSO₄ + 2H₂O