[Solved] Research has been conducted on molybdates as replacements for chromates in the surface treatment of various metals

Research has been conducted on molybdates as replacements for chromates in the surface treatment of various metals in order to reduce corrosion by the formation of a surface film of MoO2. The overall reaction with iron is

2Fe(s) + 3M004-(aq) + 6H+ (aq) → Fe2O3(s) + 3M002(s) + 3H20(1)

Given the following standard chemical potentials (μ°) in calories per mole at 25°C Fe2O3 (s) =-177, 100, M002 (s) =-120,000, H2O (l) =-56,690, MoO4-2 (aq) 205,420:

(a) Is the above overall reaction spontaneous under standard conditions?

(b) Calculate the standard electrode potential for the above overall reaction.

(c) Write an expression for the electrode potential as a function of molybdate ion concentration and pH. 7.0? suggest about the possibility of molybdates as chromate replacements?

(d) Is the overall reaction spontaneous for a molybdate ion concentration of 0.001 M at pH

(e) Based solely on thermodynamic considerations, what do the results in (a) and (d)

Expert Answer

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