Examine the following half-reactions and select the strongest oxidizing agent among the species listed. Cr2+(aq) + 2e– LaTeX: \longrightarrow⟶Cr(s) E° = –0.913 V Fe2+(aq) + 2e– LaTeX: \longrightarrow⟶ Fe(s) E° = –0.447 V Sr2+(aq) + 2e– LaTeX: \longrightarrow⟶ Sr(s) E° = –2.89 V Co2+(aq) + 2e– LaTeX: \longrightarrow⟶ Co(s) E° = –0.28 V

Challenge question: this question is worth 6 points. as you saw in problem 9 we can have species bound to a central metal ion. these species are called ligands. in the past we have assumed all the d orbitals in some species are degenerate; however, they often are not. sometimes the ligands bound to a central metal cation can split the d orbitals. that is, some of the d orbitals will be at a lower energy state than others. ligands that have the ability to cause this splitting are called strong field ligands, cnâ’ is an example of these. if this splitting in the d orbitals is great enough electrons will fill low lying orbitals, pairing with other electrons in a given orbital, before filling higher energy orbitals. in question 7 we had fe2+, furthermore we found that there were a certain number (non-zero) of unpaired electrons. consider now fe(cn)6 4â’: here we also have fe2+, but in this case all the electrons are paired, yielding a diamagnetic species. how can you explain this?