Cobalt standard electrode potential

Symbol Ni atomic number 28 atomic weight 58.693 a transition metal element in the first triad of Group VIll(Group 10) after iron and cobalt electron configuration [Ar]3d 4s2 valence states 0, -i-l, +2, and -f-3 most common oxidation state +2 the standard electrode potential, NF+ -1- 2e Ni -0.237 V atomic radius 1.24A ionic radius (NF+) 0.70A five natural isotopes Ni-58 (68.08%), Ni-60 (26.22%), Ni-61 (1.14%), Ni-62 (3.63%), Ni-64 (0.93%) nineteen radioactive isotopes are known in the mass range 51-57, 59, 63, 65-74 the longest-lived radioisotope Ni-59 has a half-life 7.6x10 years. 

A voltaic cell is made from a Co (aq)/Co(s) halfcell and a Cu (aq)/Cu(s) half-cell. The cell potential was +0.62 V, with the copper half-cell positive. Calculate the standard electrode potential of the cobalt half-cell. 

Cob(III)alamins undergo ligand exchange reactions typical of cobalt(III) complexes, most of which are not directly relevant to biological function. One-electron reduction to cob(II)alamin and two-electron reduction to cob(I)alamin are biologically relevant. The standard reduction potentials are +200 and —610 mV, respectively, for the base-on Cob(III)/Cob(II) and Cob(II)/Cob(I) couples, referenced to the normal hydrogen electrode. ... 

Several investigations have been made of the reduction of cobalt(II) to cobalt(O) in molten salt media. Eor a eutectic melt of LiCl-KCl at 450°C[10], a 1 1 NaCl-KCl melt at 450°C[11], and a MgCh-NaCl-KCl (50 30 20 mol%) mixture at 475 °C [12], the apparent standard potentials for the cobalt(II)-cobalt(0) couple have been deduced to be —1.207 V, — 1.277 V, and—1.046 V, respectively, each with respect to a chlorine-chloride ion reference electrode. 

Applying a variable potential-independent value between the electrodes induces the occurrence of the electrochemical reactions. Each cobalt species responds at a specific potential with a resulting diffusion-limited current proportional to its concentration in the medium. A representative voltammogram is reproduced in Fig. 4. The use of standard solutions of Co(II) and Co(III) complexes for calibration allowed for the quantitative determination of the concentration of each component. This methodology was found to be applicable for in-process reaction monitoring purposes, as well as for establishing Co(II) impurity levels in the isolated product (typically not detected). 

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