Question 1

Calculate Ecell for the following electrochemical cell at 25 °C. Pt(s) | Fe3+(aq, 0.100 M), Fe2+(aq, 0.040 M) || Cl-(aq, 0.50 M) | AgCl(s) | Ag(s)
The standard reduction potentials are as follows:
AgCl(s) + e- → Ag(s) + Cl-(aq)
E° = +0.222 V
Fe3+(aq) + e- → Fe2+(aq)
E° = +0.771 V

Accepted Answer

A)   -1.034 V
B)   -0.590 V
C)   -0.508 V
D)   -0.555 V
E)   +1.034 V D

Question 2

Which of the following statements is true for electron transfer reactions?

Accepted Answer

A)   One reactant is oxidized and one reactant is reduced.
B)   The extent of oxidation and reduction need not be balanced.
C)   The oxidizing agent is oxidized.
D)   The reducing agent is reduced.
E)   An increase in oxidation number represents reduction. A

Question 3

Write a balanced net ionic equation for the reaction below in an acidic solution.
Cr2O72-(aq) + Ni(s) ? Cr3+(aq) + Ni2+(aq)

Accepted Answer

A)   Cr2O72-(aq)  + 3 Ni(s)  + 14 H+(aq)  ? 2 Cr3+(aq)  + 3 Ni2+(aq)  + 7 H2O(  ℓ\ellℓ  ) 
B)   Cr2O72-(aq)  + Ni(s)  + 14 H+(aq)  ? 2 Cr3+(aq)  + Ni2+(aq)  + 7 H2O(  ℓ\ellℓ  ) .
C)   Cr2O72-(aq)  + 3 Ni(s)  ? 2 Cr3+(aq)  + 3 Ni2+(aq)  + O2-(aq) 
D)   Cr2O72-(aq)  + Ni(s)  + 14 H+(aq)  ? 2 Cr3+(aq)  + Ni2+(aq)  + 7 H2O(  ℓ\ellℓ  ) 
E)   Cr2O72-(aq)  + 3 Ni(s)  + 7 H+(aq)  ? 2 Cr3+(aq)  + 3 Ni2+(aq)  + 7 OH-(aq)   A

Question 4

Write a balanced chemical equation for the following reaction in a basic solution. 
ClO-(aq) + Cr(OH)3(s) ? Cl-(aq) + CrO42-(aq)

Accepted Answer

A)   3 ClO-(aq)  + 2 Cr(OH) 3(s)  + 4 OH-(aq)  ? 3 Cl-(aq)  + 2 CrO42-(aq)  + 5 H2O(  ℓ\ellℓ  ) 
B)   ClO-(aq)  + Cr(OH) 3(s)  + 3 OH-(aq)  ? Cl-(aq)  + CrO42-(aq)  + 3 H2O(  ℓ\ellℓ  ) 
C)   2 ClO-(aq)  + 3 Cr(OH) 3(s)  + 3 OH-(aq)  ? 2 Cl-(aq)  + 3 CrO42-(aq)  + 6 H2O(  ℓ\ellℓ  ) 
D)   4 ClO-(aq)  + Cr(OH) 3(s)  + 4 OH-(aq)  ? Cl-(aq)  + CrO42-(aq)  + 6 H2O(  ℓ\ellℓ  ) 
E)   ClO-(aq)  + Cr(OH) 3(s)  ? Cl-(aq)  + CrO42-(aq)  + 3 H+(aq)

Question 5

Write the balanced oxidation half-reaction for the following overall reaction: 
2 H+(aq) + Ca(s) → Ca2+(aq) + H2(g)

Accepted Answer

A)   Ca(s)   → 2e- + Ca2+ (aq) 
B)   2 H+(aq)  → H2(g)  + 2 e-
C)   H2(g)  → 2 H+(aq)  + 2 e-
D)   Ca(s)  + 2 e- → Ca2+(aq) 
E)   2Ca(s)  → Ca2+(aq)  + 2 e-

Question 6

Calculate the value of the reaction quotient, Q, for the voltaic cell constructed from the following two half-reactions when the Zn2+ion concentration is 0.0110 M and the Ag+ ion concentration is 1.27 M? 
$\mathrm { Zn } ^ { 2 + } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - }$ ? $\mathrm { Zn } ( \mathrm { s } ) ; E ^ { \circ } = - 0.76 \mathrm {~V}$ $\mathrm { Ag } ^ { + } ( \mathrm { aq } ) + \mathrm { e } ^ { - }$ ? $\mathrm { Ag } ( \mathrm { s } ) ; E ^ { \circ } = 0.80 \mathrm {~V}$

Accepted Answer

A)   8.66 × 10-3
B)   6.82 × 10-3
C)   115
D)   1.25 × 10-2
E)   147

Question 7

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction? 
3 Sn4+(aq) + 2 Cr(s) → 3 Sn2+(aq) + 2 Cr3+(aq)

Accepted Answer

A)   Sn4+(aq)  is the reducing agent and Cr(s)  is the oxidizing agent.
B)   Cr(s)  is the reducing agent and Sn2+(aq)  is the oxidizing agent.
C)   Sn4+(aq)  is the reducing agent and Sn2+(aq)  is the oxidizing agent.
D)   Cr(s)  is the reducing agent and Cr3+(aq)  is the oxidizing agent.
E)   Cr(s)  is the reducing agent and Sn4+(aq)  is the oxidizing agent.

Question 8

Write a balanced chemical equation for the oxidation of solid cadmium by concentrated nitric acid, producing nitrogen dioxide gas and Cd2+(aq) ion.

Accepted Answer

A)   HNO3(aq)  + Cd(s)  ? Cd2+(aq)  + NO2(g)  + OH-(aq) 
B)   2 HNO3(aq)  + Cd(s)  ? Cd2+(aq)  + 2 NO2(g)  + 2 OH-(aq) 
C)   HNO3(aq)  + Cd(s)  + H+(aq)  ? Cd2+(aq)  + NO2(g)  + H2O(  ℓ\ellℓ  ) 
D)   4 HNO3(aq)  + Cd(s)  ? Cd2+(aq)  + 2 NO2(g)  + 2 H2O(  ℓ\ellℓ  )  + 2 NO3-(aq) 
E)   HNO3(aq)  + Cd(s)  ? Cd2+(aq)  + NO2(g)

Question 9

Write the balanced reduction half-reaction for the following overall reaction: 
2 Fe(s) + 3 Cl2(aq) → 2 Fe3+(aq) + 6 Cl-(aq)

Accepted Answer

A)   Cl2(aq)  + 2 e- → 2 Cl-(aq) 
B)   Fe(s)  + 3 e- → Fe3+(aq) 
C)   Fe(s)  + Cl2(aq)  → FeCl3(aq) 
D)   Cl2(aq)  → 2 Cl-(aq)  + 2 e-
E)   3 Cl2(aq)  + 2 e- → 2 Cl-(aq)

Question 10

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent. 
Fe2+(aq) + 2 e- ? Fe(s); E° = -0.41 V
Pt2+(aq) + 2 e- ? Pt(s); E° = 1.18 V
Cr2O72-(aq) + 14 H+(aq) + 6 e- ? 2 Cr3+(aq) + 7 H2O( $\ell$ ); E° = 1.33 V

Accepted Answer

A)   Fe
B)   Pt
C)   Cr3+
D)   Fe2+
E)   Cr2O72-

Question 11

Aluminum(III) ion (Al3+) is reduced to solid aluminum at an electrode. If a current of 2.75 amperes is passed for 36 hours, calculate the mass of aluminum deposited at the electrode. (Assume 100% current efficiency.)

Accepted Answer

A)   9.2 × 10-3 g
B)   3.3 × 101 g
C)   9.9 × 101 g
D)   1.0 × 102 g
E)   3.0 × 102 g

Question 12

Calculate the equilibrium constant for the reaction below at 25 °C. Co(s) + 2 Cr3+(aq) → Co2+(aq) + 2 Cr2+(aq)
The standard reduction potentials are as follows:
Co2+(aq) + 2 e- → Co(s)
E° = -0.28 V
Cr3+(aq) + e- → Cr2+(aq)
E° = -0.41 V

Accepted Answer

A)   4.0 × 10-5
B)   2.5 × 104
C)   1.0 × 105
D)   1.2 × 105
E)   1.3 × 105

Question 13

Calculate the copper(II) ion concentration at 25 °C in the cell Zn(s) | Zn2+(aq, 1.0 M) || Cu2+(aq) | Cu(s) if the measured cell potential is 1.06 V. The standard cell potential is 1.10 V.

Accepted Answer

A)   0.21 M
B)   1.0 M.
C)   0.045 M
D)   1.0 M..
E)   1.0 M

Question 14

If the $E _ { \text {cell } } ^ { \circ }$ = -0.362 V for a given electrochemical cell at 25 °C, calculate the pH of the solution at the cathode. Pt | H2(g, 1.0 atm) | H+(aq, 1.00 M) || H+(aq) | H2(g, 1.0 atm) | Pt

Accepted Answer

A)   1.77
B)   3.06
C)   6.11
D)   7.89
E)   12.23

Question 15

Use the following standard reduction potentials to determine which species is the best oxidizing agent. 
$$\begin{array} { l l } 
\mathrm { O } _ { 2 } ( \mathrm {~g} ) + 4 \mathrm { H } ^ { + } ( \mathrm { aq } ) + 4 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { H } _ { 2 } \mathrm { O } ( \ell ) & E ^ { \circ } = + 1.229 \mathrm {~V} \
\mathrm {{ Hg } _ { 2 }} ^ { 2 + } ( \mathrm { aq } ) + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { Hg } ( \ell ) & E ^ { \circ } = + 0.789 \mathrm {~V} \
\mathrm { I } _ { 2 } ( \mathrm {~s} ) + 2 \mathrm { e } ^ { - } \rightarrow 2 \mathrm { I } ^ { - } ( \mathrm { aq } ) & E ^ { \circ } = + 0.535 \mathrm {~V}
\end{array}$$

Accepted Answer

A)   I2(s) 
B)   O2(g) 
C)   I-(aq) 
D)   Hg22+(aq) 
E)   H2O(  ℓ\ellℓ  )

Question 16

Claculate the mass of chromium that can be deposited by electrolysis of an aqueous solution of chromium(III) sulfate, Cr2(SO4)3, for 180 min using a constant current of 11.0 A. Assume 100% current efficiency. (F = 96485 C/mol)

Accepted Answer

A)   0.356 g
B)   21.3 g
C)   192.1 g
D)   0.187 g
E)   32.0 g

Question 17

When the given oxidation-reduction reaction in an acidic solution is balanced, what is the lowest whole-number coefficient for H+, and on which side of the balanced equation should it appear? 
MnO4-(aq) + Br-(aq) → Mn2+(aq) + Br2(l)

Accepted Answer

A)   1; reactant side
B)   2; product side
C)   8; reactant side
D)   16; reactant side
E)   4; product side

Question 18

Calculate the charge, in coulombs, is required to deposit 1.5 g of solid magnesium from a solution of Mg2+(aq) ion.

Accepted Answer

A)   4.1 × 102 C
B)   6.0 × 103 C
C)   1.2 × 104 C
D)   2.9 × 105 C
E)   3.1 × 106 C

Question 19

Consider the following half-reactions. 
Ag+(aq) + e- → Ag(s)
E° = +0.80 V
Cu2+(aq) + 2 e- → Cu(s)
E° = +0.34 V
Pb2+(aq) + 2 e- → Pb(s)
E° = -0.13 V
Fe2+(aq) + 2 e- → Fe(s)
E° = -0.44 V
Al3+(aq) + 3 e- → Al(s)
E° = -1.66 V
Which of the following species will oxidize lead, Pb(s)?

Accepted Answer

A)   Ag+(aq)  and Cu2+(aq) 
B)   Ag(s)  and Cu(s) 
C)   Fe2+(aq)  and Al3+(aq) 
D)   Fe(s)  and Al(s) 
E)   Cu2+(aq)  and Fe2+(aq)

Question 20

When a secondary battery provides electrical energy, it is acting as a voltaic cell. When the battery is recharging, it is operating as a(n) _____ cell.

Accepted Answer

The answer of When a secondary battery provides electrical energy,...

Exam 20: Principles of Chemical Reactivity: Electron Transfer Reactions

Which of the following statements is true for electron transfer reactions?

Write a balanced net ionic equation for the reaction below in an acidic solution. Cr₂O₇^2-(aq) + Ni(s) ? Cr³⁺(aq) + Ni²⁺(aq)

Write a balanced chemical equation for the following reaction in a basic solution. ClO^-(aq) + Cr(OH) ₃(s) ? Cl^-(aq) + CrO₄^2-(aq)

Write the balanced oxidation half-reaction for the following overall reaction: 2 H⁺(aq) + Ca(s) → Ca²⁺(aq) + H₂(g)

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction? 3 Sn⁴⁺(aq) + 2 Cr(s) → 3 Sn²⁺(aq) + 2 Cr³⁺(aq)

Write a balanced chemical equation for the oxidation of solid cadmium by concentrated nitric acid, producing nitrogen dioxide gas and Cd²⁺(aq) ion.

Write the balanced reduction half-reaction for the following overall reaction: 2 Fe(s) + 3 Cl2(aq) → 2 Fe3+(aq) + 6 Cl-(aq)

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent. Fe²⁺(aq) + 2 e^- ? Fe(s) ; E° = -0.41 V Pt²⁺(aq) + 2 e^- ? Pt(s) ; E° = 1.18 V Cr₂O₇^2-(aq) + 14 H⁺(aq) + 6 e^- ? 2 Cr³⁺(aq) + 7 H₂O( $\ell$ ) ; E° = 1.33 V

Aluminum(III) ion (Al³⁺) is reduced to solid aluminum at an electrode. If a current of 2.75 amperes is passed for 36 hours, calculate the mass of aluminum deposited at the electrode. (Assume 100% current efficiency.)

Calculate the equilibrium constant for the reaction below at 25 °C. Co(s) + 2 Cr³⁺(aq) → Co²⁺(aq) + 2 Cr²⁺(aq) The standard reduction potentials are as follows: Co²⁺(aq) + 2 e^- → Co(s) E° = -0.28 V Cr³⁺(aq) + e^- → Cr²⁺(aq) E° = -0.41 V

Calculate the copper(II) ion concentration at 25 °C in the cell Zn(s) | Zn²⁺(aq, 1.0 M) || Cu²⁺(aq) | Cu(s) if the measured cell potential is 1.06 V. The standard cell potential is 1.10 V.

If the $E _ { \text {cell } } ^ { \circ }$ = -0.362 V for a given electrochemical cell at 25 °C, calculate the pH of the solution at the cathode. Pt | H₂(g, 1.0 atm) | H⁺(aq, 1.00 M) || H⁺(aq) | H₂(g, 1.0 atm) | Pt

Claculate the mass of chromium that can be deposited by electrolysis of an aqueous solution of chromium(III) sulfate, Cr₂(SO₄) ₃, for 180 min using a constant current of 11.0 A. Assume 100% current efficiency. (F = 96485 C/mol)

When the given oxidation-reduction reaction in an acidic solution is balanced, what is the lowest whole-number coefficient for H⁺, and on which side of the balanced equation should it appear? MnO₄^-(aq) + Br^-(aq) → Mn²⁺(aq) + Br₂(l)

Calculate the charge, in coulombs, is required to deposit 1.5 g of solid magnesium from a solution of Mg²⁺(aq) ion.

When a secondary battery provides electrical energy, it is acting as a voltaic cell. When the battery is recharging, it is operating as a(n) _____ cell.

Exam 20: Principles of Chemical Reactivity: Electron Transfer Reactions

Calculate Ecell for the following electrochemical cell at 25 °C. Pt(s) | Fe3+(aq, 0.100 M) , Fe2+(aq, 0.040 M) || Cl-(aq, 0.50 M) | AgCl(s) | Ag(s) The standard reduction potentials are as follows: AgCl(s) + e- → Ag(s) + Cl-(aq) E° = +0.222 V Fe3+(aq) + e- → Fe2+(aq) E° = +0.771 V

Which of the following statements is true for electron transfer reactions?

Write a balanced net ionic equation for the reaction below in an acidic solution. Cr2O72-(aq) + Ni(s) ? Cr3+(aq) + Ni2+(aq)

Write a balanced chemical equation for the following reaction in a basic solution. ClO-(aq) + Cr(OH) 3(s) ? Cl-(aq) + CrO42-(aq)

Write the balanced oxidation half-reaction for the following overall reaction: 2 H+(aq) + Ca(s) → Ca2+(aq) + H2(g)

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction? 3 Sn4+(aq) + 2 Cr(s) → 3 Sn2+(aq) + 2 Cr3+(aq)

Write a balanced chemical equation for the oxidation of solid cadmium by concentrated nitric acid, producing nitrogen dioxide gas and Cd2+(aq) ion.

Write the balanced reduction half-reaction for the following overall reaction: 2 Fe(s) + 3 Cl2(aq) → 2 Fe3+(aq) + 6 Cl-(aq)

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent. Fe2+(aq) + 2 e- ? Fe(s) ; E° = -0.41 V Pt2+(aq) + 2 e- ? Pt(s) ; E° = 1.18 V Cr2O72-(aq) + 14 H+(aq) + 6 e- ? 2 Cr3+(aq) + 7 H2O( ℓ\ellℓ ) ; E° = 1.33 V

Aluminum(III) ion (Al3+) is reduced to solid aluminum at an electrode. If a current of 2.75 amperes is passed for 36 hours, calculate the mass of aluminum deposited at the electrode. (Assume 100% current efficiency.)

Calculate the equilibrium constant for the reaction below at 25 °C. Co(s) + 2 Cr3+(aq) → Co2+(aq) + 2 Cr2+(aq) The standard reduction potentials are as follows: Co2+(aq) + 2 e- → Co(s) E° = -0.28 V Cr3+(aq) + e- → Cr2+(aq) E° = -0.41 V

Calculate the copper(II) ion concentration at 25 °C in the cell Zn(s) | Zn2+(aq, 1.0 M) || Cu2+(aq) | Cu(s) if the measured cell potential is 1.06 V. The standard cell potential is 1.10 V.

If the Ecell ∘E _ { \text {cell } } ^ { \circ }Ecell ∘​ = -0.362 V for a given electrochemical cell at 25 °C, calculate the pH of the solution at the cathode. Pt | H2(g, 1.0 atm) | H+(aq, 1.00 M) || H+(aq) | H2(g, 1.0 atm) | Pt

Claculate the mass of chromium that can be deposited by electrolysis of an aqueous solution of chromium(III) sulfate, Cr2(SO4) 3, for 180 min using a constant current of 11.0 A. Assume 100% current efficiency. (F = 96485 C/mol)

When the given oxidation-reduction reaction in an acidic solution is balanced, what is the lowest whole-number coefficient for H+, and on which side of the balanced equation should it appear? MnO4-(aq) + Br-(aq) → Mn2+(aq) + Br2(l)

Calculate the charge, in coulombs, is required to deposit 1.5 g of solid magnesium from a solution of Mg2+(aq) ion.

Consider the following half-reactions. Ag+(aq) + e- → Ag(s) E° = +0.80 V Cu2+(aq) + 2 e- → Cu(s) E° = +0.34 V Pb2+(aq) + 2 e- → Pb(s) E° = -0.13 V Fe2+(aq) + 2 e- → Fe(s) E° = -0.44 V Al3+(aq) + 3 e- → Al(s) E° = -1.66 V Which of the following species will oxidize lead, Pb(s) ?

When a secondary battery provides electrical energy, it is acting as a voltaic cell. When the battery is recharging, it is operating as a(n) _____ cell.

Write a balanced net ionic equation for the reaction below in an acidic solution. Cr₂O₇^2-(aq) + Ni(s) ? Cr³⁺(aq) + Ni²⁺(aq)

Write a balanced chemical equation for the following reaction in a basic solution. ClO^-(aq) + Cr(OH) ₃(s) ? Cl^-(aq) + CrO₄^2-(aq)

Write the balanced oxidation half-reaction for the following overall reaction: 2 H⁺(aq) + Ca(s) → Ca²⁺(aq) + H₂(g)

Which of the following statements is true for the following reaction, assuming the given reaction proceeds in the forward direction? 3 Sn⁴⁺(aq) + 2 Cr(s) → 3 Sn²⁺(aq) + 2 Cr³⁺(aq)

Write a balanced chemical equation for the oxidation of solid cadmium by concentrated nitric acid, producing nitrogen dioxide gas and Cd²⁺(aq) ion.

Use the following standard reduction potentials to determine which species is the strongest oxidizing agent. Fe²⁺(aq) + 2 e^- ? Fe(s) ; E° = -0.41 V Pt²⁺(aq) + 2 e^- ? Pt(s) ; E° = 1.18 V Cr₂O₇^2-(aq) + 14 H⁺(aq) + 6 e^- ? 2 Cr³⁺(aq) + 7 H₂O( $\ell$ ) ; E° = 1.33 V

Aluminum(III) ion (Al³⁺) is reduced to solid aluminum at an electrode. If a current of 2.75 amperes is passed for 36 hours, calculate the mass of aluminum deposited at the electrode. (Assume 100% current efficiency.)

Calculate the equilibrium constant for the reaction below at 25 °C. Co(s) + 2 Cr³⁺(aq) → Co²⁺(aq) + 2 Cr²⁺(aq) The standard reduction potentials are as follows: Co²⁺(aq) + 2 e^- → Co(s) E° = -0.28 V Cr³⁺(aq) + e^- → Cr²⁺(aq) E° = -0.41 V

Calculate the copper(II) ion concentration at 25 °C in the cell Zn(s) | Zn²⁺(aq, 1.0 M) || Cu²⁺(aq) | Cu(s) if the measured cell potential is 1.06 V. The standard cell potential is 1.10 V.

If the $E _ { \text {cell } } ^ { \circ }$ = -0.362 V for a given electrochemical cell at 25 °C, calculate the pH of the solution at the cathode. Pt | H₂(g, 1.0 atm) | H⁺(aq, 1.00 M) || H⁺(aq) | H₂(g, 1.0 atm) | Pt

Claculate the mass of chromium that can be deposited by electrolysis of an aqueous solution of chromium(III) sulfate, Cr₂(SO₄) ₃, for 180 min using a constant current of 11.0 A. Assume 100% current efficiency. (F = 96485 C/mol)

When the given oxidation-reduction reaction in an acidic solution is balanced, what is the lowest whole-number coefficient for H⁺, and on which side of the balanced equation should it appear? MnO₄^-(aq) + Br^-(aq) → Mn²⁺(aq) + Br₂(l)

Calculate the charge, in coulombs, is required to deposit 1.5 g of solid magnesium from a solution of Mg²⁺(aq) ion.