Please help. 1. The electrolysis of molten Al2O3 at 980 ºC is used to produce me
ID: 694148 • Letter: P
Question
Please help.
1. The electrolysis of molten Al2O3 at 980 ºC is used to produce metallic aluminum. A current of 758 A is used in the electrolysis cell. What is the rate of formation of aluminum, in kilograms per hour?
2. For the above current at 3.25 V, how much electrical energy (in kw-hr) is consumed in the production of 1 kg of aluminum? (The electrical energy or work =qV and 1 kW-hr is 3.6 x106 J.)
3. Air is 21 mole percent oxygen, that is, 0.21 atm oxygen at 1 atm. Suppose the pH of the water is 4.42 and that the concentration of iron(II) in the water is 8.71x 10-5 M, what is the potential of the corrosion reaction under the above conditions at 298 K?
4. The standard free energy change at 25 oC, Go, is equal to -64.9 kJ for
2X(CN)63-(aq) + 2I-(aq) 2X(CN)64-(aq) + I2(s).
Calculate the standard potential for this reaction. Normally, X is Fe. Here it is some unknown metal, allowing for somewhat random values for Go.
5. Calculate the potential of the Pb/Pb(IO3)2 electrode in a 0.00545 M solution of NaIO3.
Explanation / Answer
Ans 1 :
Al3+ + 3e- = Al
One mole of Al requires 3 moles of electrons.
Q = I . t
Q = 758 x 3600
Q = 2728800 C
Number of moles of electrons = 2728800 / 96487 = 28.28 moles
So number of moles of Al reduced = 28.28 / 3 = 9.427 moles
Mass of Al = 9.427 x 26.98 = 254.345 g
So the rate of formation of Aluminium will be 0.254 kg/ hr