Given the following half-reactions and E° values, write a balanced equation for the formation of Mn2+ and MnO2 from Mn3+, and calculate the value of E° for this reaction. Is the reaction spontaneous under standard-state conditions?

Verified step by step guidance

1. Identify the given half-reactions and their standard reduction potentials (E° values).
2. Write the half-reactions for the reduction and oxidation processes involving Mn species.
3. Balance the electrons transferred in the half-reactions to ensure the overall charge is balanced.
4. Combine the balanced half-reactions to form the overall balanced equation for the reaction.
5. Calculate the standard cell potential (E°) for the reaction by using the formula E° = E°(reduction) - E°(oxidation) and determine if the reaction is spontaneous by checking if E° is positive.

Key Concepts

Half-Reactions

Half-reactions represent the oxidation and reduction processes occurring in an electrochemical reaction. Each half-reaction shows the transfer of electrons, with one species being oxidized (losing electrons) and another being reduced (gaining electrons). Understanding how to write and balance these half-reactions is crucial for determining the overall reaction and its electrochemical properties.

Standard Electrode Potential (E°)

The standard electrode potential (E°) is a measure of the tendency of a chemical species to be reduced, measured under standard conditions (1 M concentration, 1 atm pressure, and 25°C). It is expressed in volts and is used to predict the direction of electron flow in electrochemical cells. The overall E° for a reaction can be calculated by subtracting the E° of the oxidation half-reaction from that of the reduction half-reaction.

Spontaneity of Reactions

The spontaneity of a reaction under standard-state conditions can be determined using the Gibbs free energy change (ΔG). A negative ΔG indicates that a reaction is spontaneous, while a positive ΔG suggests it is non-spontaneous. The relationship between E° and ΔG is given by the equation ΔG = -nFE°, where n is the number of moles of electrons transferred and F is Faraday's constant. Thus, a positive E° corresponds to a spontaneous reaction.