(b) At high pH, the principal products are oxygen and manganese(IV) as the dioxide:

(c) Alkaline fusion of manganese dioxide produces Mn(VI) ions in a disproportionation reaction:

81. Redox reactions:

82. The Daniell cell: the half-cells are filled with copper(II) sulfate and zinc(II) sulfate solutions, respectively, at concentrations of 1M, and the cell voltage is measured. Write the half-reactions, look up the E° values in the table of standard reduction potentials in your textbook and calculate E°_cell. Compare that result with the experimental value.

83. Electrolysis of an aqueous sodium sulfate solution: In this second demonstration of the electrolysis of water, the design of the apparatus allows us to study the acid/base chemistry and the stoichiometry of the reaction. You should be able to write the balanced half-reactions for the oxidation and reduction half-reactions, and the complete cell reaction, identify the anode and the cathode, the (+) and (-) terminals, and why the chemistry turns the solutions in the vicinity of the electrodes acidic or basic.

84. Strange cells: Apple cell; orange cell; pickle cell; potato cell.

85. The Hooker cell: The electrolysis of saturated NaCl solutions is the basis for the commercial preparation of Cl₂ and NaOH solutions. Write the half-reactions, identify the anode and cathode processes, and consider how this electrolysis differs from the electrolysis of acidified tap water or aqueous sodium sulfate solutions.

86. Electricity from chemistry, for lighting: Powdered iodine is placed in a porous porcelain cup filled with a potassium iodide (KI) solution and fitted with a carbon rod and a zinc metal strip connected to a light bulb. Based on the demonstration, sketch the cell, indicate the electrochemical result, and write the half-reactions for the anode and the cathode, and the net reaction.

87. Copper Plating: A platinum gauze can be copper-plated using an acidified solution of copper(II) sulfate, a copper foil anode, and a 6V direct current. By revrsing the polarity of the cell, the plated copper can be removed. Write the half-reactions and the net overall reaction for each process.

88. 12-V Standard automoble storage battery: Cut in half. Check out the electrodes and basic construction. Why doesn't it run forever?

89. Mossy zinc in the presence of Cu(II) ions (copper sulfate solution) deposits copper from solution:

90. Ammonia burns in an oxygen atmosphere:

91. The easy oxidation of reducing sugars by Tollen's reagent, an aqueous silver ammonia complex solution, has long been used in organic chemistry to indicate the presence of the aldehyde group. Using the general formula RCHO and RCOOH in the equation below, where R is any other carbon fragment bonded to the aldehyde and carboxylic acid groups, the equation is simply written to show the formation of the silver mirror:

Try to write half-reactions for this process. (HINT: assume the C atom in RCHO is in the -1 state and the C atom in RCOOH is in the +3 state. Do you see why?)