The standard reduction potentials at 25°C for the following half reactions are :Zn2+(aq) + 2e– ⇌ Zn(s), E°RP = –0.762VCr2+(aq) + 3e– ⇌ Cr(s), E°RP = –0.740V2H+(aq) + 2e– ⇌ H2(g), E°RP = 0.00VFe3+(aq) + 2e– ⇌ Fe2+(aq), E°RP = 0.77 VWhich is the strongest reducing agent ?

Standard reduction potentials of the half reactions are given belowNi2+ + 2e– → Ni(s); E° = –0.25 VPb2+ + 2e– → Pb(s); E° = –0.13 VMg2+ + 2e– → Mg(s); E° = –2.36 VCa2+ + 2e– → Ca(s); E° = –2.87 VThe strongest oxidising and reducing agents are respectivelyMg2+ and NiPb2+ and CaCa2+ and PbNi2+ and Pb

Consider the cell potentials E∘Mg2+|Mg = −2.37V and E∘Fe2+|Fe = −0.04V . The best reducing agent among the above would be:

The standard reduction potential value of these metallic cations x, y & z are 0.52, –3.303 & –1.18 V respectively. The order of reducing power of the corresponding metals is

The tendency of a chemical species to undergo reduction during an electrochemical reaction is indicated by the standard potential E° for the reaction.  As represented generally by Reaction 1, E° measures the potential Z at which element X with oxidation number N accepts N electrons and is reduced to its elemental state.X(N) + Ne− → X(0), E° = Z voltsReaction 1In a galvanic cell, E° > 0 indicates a spontaneous reaction.  Therefore, chemical species with higher positive E° values are reduced more easily than those with lower E° values.Using E° as a basis of comparison, the relative thermodynamic stabilities of different chemical species involving the same element at different oxidation states can be presented graphically using a Frost diagram.  For a series of compounds containing element X, a Frost diagram plots the value of NE° for each compound against the corresponding oxidation number N of element X within the species.  Frost diagrams for several species containing manganese or chlorine are shown in Figure 1.Figure 1  Frost diagrams for manganese and chlorineOn a Frost diagram, NE° is proportional to the standard Gibbs free energy ΔG° according to the relationshipΔG° = −FNE° = −nFE°Equation 1where n is the number of moles of electrons transferred during the electrochemical process and F is the Faraday constant.  Free energy considerations also show that a species is prone to disproportionation if its position on the Frost diagram lies above a line connecting the points of two adjacent species, as seen for species B in Figure 2.Figure 2  General Frost diagram for an element forming species A, B, C, and D.The slope of a line segment joining two species on a Frost diagram is equal to the standard reduction potential for the couple.  A greater slope indicates a higher corresponding reduction potential.  As a result, in Figure 2, the reduction potential for B to A is lower than that for D to C. Question 42Based on the passage, which of the following species is LEAST likely to undergo a disproportionation reaction?A.H3MnO4, pH = 0B.MnO43−, pH = 14C.Mn3+, pH = 0D.MnO2, pH = 14

In the following ionic reaction, identify the reducing agent: Fe + 2H+ → Fe2+ + H2