20. Electrochemistry

Which of the following correctly describes the products of the electrolysis of an aqueous solution of KI?

The diagram that follows represents a molecular view of a process occurring at an electrode in a voltaic cell.

(b) Is the electrode the anode or cathode?

The diagram that follows represents a molecular view of a process occurring at an electrode in a voltaic cell.

(a) Does the process represent oxidation or reduction?

Assume that you want to construct a voltaic cell that uses the following half-reactions: A2+1aq2 + 2 e- ¡ A1s2 Ered ° = -0.10 V B2+1aq2 + 2 e- ¡ B1s2 E°red = -1.10 V You begin with the incomplete cell pictured here in which the electrodes are immersed in water.

(a) What additions must you make to the cell for it to generate a standard emf?

Indicate whether each statement is true or false: (c) A salt bridge or permeable barrier is necessary to allow a voltaic cell to operate.

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?

(b) Do all voltaic cells produce a positive cell potential?

(c) Why is it impossible to measure the standard reduction potential of a single half-reaction?

A voltaic cell that uses the reaction PdCl42-1aq2 + Cd1s2 ¡ Pd1s2 + 4 Cl-1aq2 + Cd2+1aq2 has a measured standard cell potential of +1.03 V. (a) Write the two half-cell reactions.

Porous pellets of TiO2 can be reduced to titanium metal at the cathode of an electrochemical cell containing molten CaCl2 as the electrolyte. When the TiO2 is reduced, the O2-ions dis-solve in the CaCl2 and are subsequently oxidized to O2 gas at the anode. This approach may be the basis for a less expensive process than the one currently used for producing titanium.

(a) Label the anode and cathode, and indicate the signs of the electrodes.

A voltaic cell consists of a strip of cadmium metal in a solution of Cd1NO322 in one beaker, and in the other beaker a platinum electrode is immersed in a NaCl solution, with Cl2 gas bubbled around the electrode. A salt bridge connects the two beakers. (c) Write the equation for the overall cell reaction.

Sketch a voltaic cell for each redox reaction. Label the anode and cathode and indicate the half-reaction that occurs at each electrode and the species present in each solution. Also indicate the direction of electron flow. a. Ni2+(aq) + Mg(s) ¡ Ni(s) + Mg2+(aq)

Consider the voltaic cell:

d. Indicate the direction of anion and cation flow in the salt bridge

Why is the cathode of a galvanic cell considered to be the positive electrode?

What is the function of a salt bridge in a galvanic cell?

Describe galvanic cells that use the following reactions. In each case, write the anode and cathode half-reactions and sketch the experimental setup. Label the anode and cathode, identify the sign of each electrode, and indicate the direction of electron and ion flow. (b)

Describe galvanic cells that use the following reactions. In each case, write the anode and cathode half-reactions and sketch the experimental setup. Label the anode and cathode, identify the sign of each electrode, and indicate the direction of electron and ion flow. (b)

Determine whether or not each metal dissolves in 1 M HCl. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves. a. Al

Determine whether or not each metal dissolves in 1 M HNO3. For those metals that do dissolve, write a balanced redox reaction showing what happens when the metal dissolves. a. Cu

Determine whether or not each metal dissolves in 1 M HIO3. For those metals that do dissolve, write a balanced redox equation for the reaction that occurs. a. Au

An H2/H+ half-cell (anode) and an Ag+/Ag half cell (cathode) are connected by a wire and a salt bridge. (b) Write balanced equations for the electrode and overall cell reactions.

What conditions must be met for a cell potential E to qualify as a standard cell potential E°?

In some applications nickel–cadmium batteries have been replaced by nickel–zinc batteries. The overall cell reaction for this relatively new battery is: 2 H2O1l2 + 2 NiO1OH21s2 + Zn1s2 ¡ 2 Ni1OH221s2 + Zn1OH221s2 (b)What is the anode half-reaction?

Make a sketch of a concentration cell employing two Zn/Zn2+ half-cells. The concentration of Zn2+ in one of the half-cells is 2.0 M and the concentration in the other half-cell is 1.0x10^-3 M. Label the anode and the cathode and indicate the half-reaction occuring at each electrode. Also indicate the direction of electron flow.

Consider the concentration cell: b. Indicate the direction of electron flow.

Consider the concentration cell:

c. Indicate what happens to the concentration of Pb2+ in each half-cell.

Consider the electrolytic cell: b. Indicate the direction of electron flow.

Make a sketch of an electrolysis cell that electroplates copper onto other metal surfaces. Label the anode and the cathode and indicate the reactions that occur at each.

(a) Sketch a cell with inert electrodes suitable for the elec-trolysis of an aqueous solution of sulfuric acid. Label the anode and cathode, and indicate the direction of electron and ion flow. Identify the positive and negative electrodes. (b) Write balanced equations for the anode, cathode, and overall cell reactions.

The half-reactions that occur in ordinary alkaline batteries can be written as In 1999, researchers in Israel reported a new type of alkaline battery, called a 'super-iron' battery. This battery uses the same anode reaction as an ordinary alkaline battery but involves the reduction of FeO42- ion (from K2FeO4) to solid Fe(OH)3 at the cathode. (b) Write a balanced equation for the cathode half-reaction in a super-iron battery. The half-reaction occurs in a basic environment.