Manganese standard reduction potentials

Table 4. Standard Reduction Potentials for Selected Manganese Compounds...

Figure 5 Redox predominance diagrams for iron (a) and manganese (b) boundaries represent the standard reduction potential for reduction of the (thermodynamically-stable) species above the boundary to the (thermodynamically-stable) species below the boundary. If the redox predominance regions of two species (e.g., the gray regions of Fe + and Mn04 ) do not overlap along the y-axis when the two diagrams are superimposed, reaction between the two species is thermodynamically favored...

For an element exhibiting several different oxidation states in aqueous solution, we must consider a number of different half-reactions in order to obtain a clear picture of its solution chemistry. Consider manganese as an example aqueous solution species may contain manganese in oxidation states ranging from Mn(II) to Mn(VII), and equations 7.42-7.46 give half-reactions for which standard reduction potentials can be determined experimentally. 

A second novel aspect of manganese dioxide is its role as an oxidizing agent. The standard reduction potential of manganese dioxide is 1.23 V, equal to that of oxygen itself ... 

An aqueous solution of potassium permanganate (KMn04) appears deep purple. In aqueous acidic solution, the permanganate ion can be reduced to the pale-pink manganese(II) ion (Mn ). Under standard conditions, the reduction potential of an MnOijlMn half-cell is = 1.49 V. Suppose this half-cell is combined with a Zn Zn half-cell in a galvanic cell, with [Zn ] = [MnO ] = [Mn ] = [H3O ] = 1 M. (a) Write equations for the reactions at the anode and the cathode, (b) Write a balanced equation for the overall cell reaction, (c) Calculate the standard cell potential difference, A%°. 

We can confirm this by calculating the standard electrode potential for manganese acting as the anode (oxidation) and nickel acting as the cathode (reduction). 

The succession of these two steps is equivalent to the already seen reduction at three electrons of permanganate into manganese dioxide.) The standard potentials of the two new redox couples are °(MnO4"/MnO4 ) = 0.56 V and °(Mn04 /Mn02) = 0.60 V. 

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