1) What is the value of K at 298K for the following reaction? (Please give your
ID: 881934 • Letter: 1
Question
1) What is the value of K at 298K for the following reaction? (Please give your answer to two significant digits)
3A2+(aq) + 2B(s) 2B3+(aq) + 3A(s)
A2+(aq) + 2e- A(s) Eored = -0.39
B3+(aq) + 3e- B(s) Eored = -0.30
2) What is the cell potential for the spontaneous concentration cell with the reaction A3+(aq) + A(s) A(s) + A3+(aq), with concentrations of A3+ of 0.857M and 0.371M at a temperature of 310. K?
3) How many minutes will it take to electroplate 0.389 moles of copper from a solution containing Cu2+(aq) with a current of 3.55 amps?
4) What is the minimum voltage required for the electrolysis of a melt of nickel(II) chloride?
Explanation / Answer
1) Eo (cell) = Ecathode-Eanode
= -0.39 - ( -0.30)
= -0.09 V
E0 = 0.0591 / n * logK
above reaction number of electrons transfered n = 6
-0.09 = 0.0591 / 6 * logK
K = 7.3 x 10^-10
2)
for thic concentration cell Eo = 0 V
Ecell = RT / nF log[A1/A2]
Ecell = 2.303 x 8.314 x 310 / 3 x 96500 log (0.857/0.371)
Ecell = 0.0074V
3)
moles of copper = 0.389
Cu atomic mass = 63.55
Cu weight = moles x atomic mass = 0.389 x 63.55 = 24.72
W= 24.72 g
Cu equivalent weight = 63.55 / 2 = 31.77
current = 3.55 A
F = 96500C
faraday's law :
W = E x i x t / 96500
24.72 = 31.77 x 3.55 x t / 96500
t = 21151.8 seconds
t = 352.5 min
4)
NiCl2 ------------------> Ni+2 + 2e-
2F electricity is required to electrolysis Ni+2
Ni+2 + 2e ----------------> Ni (s) , voltage = -0.26 V
0.26 V required.
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