For example, I came across a problem in which I was asked to determine whether the complex $\ce{[Cr(H2O)6]Cl2}$ is an oxidizing or reducing agent.

How should I proceed? My teacher told me its the EAN number that defines this. What are your views?

  • $\begingroup$ I was looking at some revision lately on this. My textbook/other refs indicated a bit about standard electrode potentials as a reference in determining a species as an oxidant or reductant. Given that there's Cl and a metal Cr, I would presume this is a reductant (note: reducing power decreases in this order: Na > Zn > Pb > H2 > Cu > Ag > Br- > Mn2+ > F-) and S-block metals are good reductants. Why not take a look at reactions (both acidic and basic) which involves this agent? $\endgroup$ – bonCodigo Jul 23 '17 at 11:09
  • $\begingroup$ Yep your approach is also right. I was thinking that since the Cr here is in +2 oxidation state it has an electronic configuration - [Ar] 3d^4 so it can do two things - $\endgroup$ – Serotonin Jul 23 '17 at 11:21
  • $\begingroup$ 1. It could gain an electron to achieve a stable [Ar] 3d^5 configuration or $\endgroup$ – Serotonin Jul 23 '17 at 11:22
  • $\begingroup$ 2. It could lose an electron to have half filled t2g subshell as per crystal field theory $\endgroup$ – Serotonin Jul 23 '17 at 11:23
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    $\begingroup$ Pardon my ignorance, but what is EAN? I cannot imagine how this EAN has anything to do with redox processes. Is it effective atomic number $Z_\text{eff}$? But then there is "number number", so I'm lost. $\endgroup$ – andselisk Jul 23 '17 at 11:36

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