GATE MT 2020 Q44. Iron is corroding in fresh water which has dissolved oxygen concentration of 15 mM. The anodic current density at an overpotential of 120 mV is ___________ A.cm^2 (round off to three decimal places). A. Anodic Tafel slope is 0.06 V. B. Diffusion coefficient of oxygen is 2.42810^-5 cm^2 S^-1. C. Diffusion layer thickness is 0.06 cm.

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Correct answer is 0.117 A cm^2.

Correct answer is 0.117 A cm^2.

But range given in offical key is 0.19 - 0.238

But range given in offical key is 0.19 – 0.238

The method will be same as calculation done above. Only difference shall be that the number of electron for this reaction shall be 4 because the oxygen reduction takes place as per following reaction. O2 +2H2O +4e =4OH- So, put n=4 while calculating limiting current density i.e. iL = (n.D.F.C)/x

The method will be same as calculation done above.

Only difference shall be that the number of electron for this reaction shall be 4 because the oxygen reduction takes place as per following reaction.

O2 +2H2O +4e =4OH-

So, put n=4 while calculating limiting current density i.e.

iL = (n.D.F.C)/x

See less0.117

0.117

See lesswrong

wrong

0.117

0.117

See lessWhy mM is taken as 10^-6??

Why mM is taken as 10^-6??

Take n=4 and as mM means milli molar which is equal to 10^-3molar.1molar is equal to moles per liter.1 liter is equal to 1000cm^3.so it is 10^-6mol/cm^2.and in question the gave units as Acm.it is wrong it is A/cm^2 which is the units of current density.

Take n=4 and as mM means milli molar which is equal to 10^-3molar.1molar is equal to moles per liter.1 liter is equal to 1000cm^3.so it is 10^-6mol/cm^2.and in question the gave units as Acm.it is wrong it is A/cm^2 which is the units of current density.

See less0.234A/cm^2

0.234A/cm^2

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how

See lesshow?

how?

0.234 please correct the answer

0.234 please correct the answer

See lessWhy is formula of limiting current density (iL) is used to get exchange current density(i0)?

Why is formula of limiting current density (iL) is used to get exchange current density(i0)?

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