Problem 21a
At 900 °C, titanium tetrachloride vapor reacts with molten magnesium metal to form solid titanium metal and molten magnesium chloride. (a) Write a balanced equation for this reaction.
Problem 21c
At 900 °C, titanium tetrachloride vapor reacts with molten magnesium metal to form solid titanium metal and molten magnesium chloride (c) Which substance is the reductant, and which is the oxidant?
Problem 22a
Hydrazine (N2H4) and dinitrogen tetroxide (N2O4) form a self-igniting mixture that has been used as a rocket propellant. The reaction products are N2 and H2O. (a) Write a balanced chemical equation for this reaction.
Problem 22c
Hydrazine (N2H4) and dinitrogen tetroxide (N2O4) form a self-igniting mixture that has been used as a rocket propellant. The reaction products are N2 and H2O. (c) Which substance serves as the reducing agent and which as the oxidizing agent?
Problem 23a,b,c,d
Complete and balance the following half-reactions. In each case, indicate whether the half-reaction is an oxidation or a reduction. (a) Sn2+(aq) → Sn4+(aq) (acidic solution) (b) TiO2(s) → Ti2+(aq) (acidic solution) (c) ClO3-(aq) → Cl-(aq) (acidic solution) (d) N2(g) → NH4+(aq) (acidic solution)
Problem 23f
Complete and balance the following half-reactions. In each case, indicate whether the half-reaction is an oxidation or a reduction. (f) SO32-1aq2 ¡ SO42-1aq2 (basic solution)
Problem 24a,b,c,d
Complete and balance the following half-reactions. In each case indicate whether the half-reaction is an oxidation or a reduction. (a) Mo3+(aq) → Mo(s) (acidic solution) (b) H2SO3(aq) → SO42-(aq) (acidic solution) (c) NO3-(aq) → NO(g) (acidic solution) (d) O2(g) → H2O(l) (acidic solution)
Problem 24g
Complete and balance the following half-reactions. In each case indicate whether the half-reaction is an oxidation or a reduction. (g) Cr(OH)3(s) → CrO42-(aq) (basic solution)
Problem 25a,b,c
Complete and balance the following equations, and identify the oxidizing and reducing agents: (a) Cr2O72-(aq) + I-(aq) → Cr3+(aq) + IO3-(aq) (acidic solution) (b) MnO4-(aq) + CH3O(1aq) → Mn2+(aq) + HCOOH(aq) (acidic solution) (c) I2(s) + OCl-(aq) → IO3-(aq) + Cl-(aq) (acidic solution)
Problem 25d
Complete and balance the following equations, and identify the oxidizing and reducing agents: As2O3(s) + NO3-(aq) → H3AsO4(aq) + N2O3(aq) (acidic solution)
Problem 25e
Complete and balance the following equations, and identify the oxidizing and reducing agents: MnO4-(aq) + Br-(aq) → MnO2(s) + BrO3-(aq) (basic solution)
Problem 26a,b,c,d
Complete and balance the following equations, and identify the oxidizing and reducing agents. (Recall that the O atoms in hydrogen peroxide, H2O2, have an atypical oxidation state.) (a) NO2-(aq) + Cr2O72-(aq) → Cr3+(aq) + NO3-(aq) (acidic solution) (b) S(s) + HNO3(aq) → H2SO3(aq) + N2O(g) (acidic solution) (c) Cr2O72- (aq) + CH3OH(aq) → HCOOH(aq) + Cr3+(aq) (acidic solution) (d) BrO3-(aq) + N2H4(g) → Br-(aq) + N2(g) (acidic solution)
Problem 26f
Complete and balance the following equations, and identify the oxidizing and reducing agents. (Recall that the O atoms in hydrogen peroxide, H2O2, have an atypical oxidation state.) H2O21aq2 + ClO21aq2 ¡ ClO2-1aq2 + O21g2 (basic solution)
- Indicate whether each statement is true or false: (a) The cathode is the electrode at which oxidation takes place. (b) A galvanic cell is another name for a voltaic cell. (c) Electrons flow spontaneously from anode to cathode in a voltaic cell.
Problem 27
- Indicate whether each statement is true or false: (a) The anode is the electrode at which oxidation takes place. (b) A voltaic cell always has a positive emf.
Problem 28
Problem 28c
Indicate whether each statement is true or false: (c) A salt bridge or permeable barrier is necessary to allow a voltaic cell to operate.
Problem 29f
A voltaic cell similar to that shown in Figure 20.5 is constructed. One electrode half-cell consists of a silver strip placed in a solution of AgNO3, and the other has an iron strip placed in a solution of FeCl2. The overall cell reaction is Fe1s2 + 2 Ag+1aq2 ¡ Fe2+1aq2 + 2 Ag1s2 (f) In which directions do the cations and anions migrate through the solution?
Problem 31a
(a) What is the definition of the volt?
Problem 31b
(b) Do all voltaic cells produce a positive cell potential?
- (a) Which electrode of a voltaic cell, the cathode or the anode, corresponds to the higher potential energy for the electrons? (b) What are the units for electrical potential? How does this unit relate to energy expressed in joules?
Problem 32
- (a) Write the half-reaction that occurs at a hydrogen electrode in acidic aqueous solution when it serves as the cathode of a voltaic cell. (b) What is standard about the standard hydrogen electrode?
Problem 33
Problem 33b
(b) Write the half-reaction that occurs at a hydrogen electrode in acidic aqueous solution when it serves as the anode of a voltaic cell.
- What conditions must be met for a reduction potential to be considered a standard reduction potential?
Problem 34
Problem 34c
(c) Why is it impossible to measure the standard reduction potential of a single half-reaction?
- A voltaic cell that uses the reaction Tl3+(aq) + 2 Cr2+(aq) → Tl+(aq) + 2 Cr3+(aq) has a measured standard cell potential of +1.19 V. (c) Sketch the voltaic cell, label the anode and cathode, and indicate the direction of electron flow.
Problem 35
Problem 36a
A voltaic cell that uses the reaction PdCl42-(aq) + Cd(s) → Pd(s) + 4 Cl-(aq) + Cd2+(aq) has a measured standard cell potential of +1.03 V. (a) Write the two half-cell reactions.
Problem 36b
A voltaic cell that uses the reaction PdCl42-(aq) + Cd(s) → Pd(s) + 4 Cl-(aq) + Cd2+(aq) has a measured standard cell potential of +1.03 V. (b) By using data from Appendix E, determine E°red for the reaction involving Pd.
Problem 36c
A voltaic cell that uses the reaction PdCl42-(aq) + Cd(s) → Pd(s) + 4 Cl-(aq) + Cd2+(aq) has a measured standard cell potential of +1.03 V. (c) Sketch the voltaic cell, label the anode and cathode, and indicate the direction of electron flow
Problem 37a
Using standard reduction potentials (Appendix E), calculate the standard emf for each of the following reactions: (a) Cl21g2 + 2 I-1aq2 ¡ 2 Cl-1aq2 + I21s2
Problem 37b
Using standard reduction potentials (Appendix E), calculate the standard emf for each of the following reactions: (b) Ni1s2 + 2 Ce4+1aq2 ¡ Ni2+1aq2 + 2 Ce3+1aq2
Ch.20 - Electrochemistry