In: Chemistry
(A) A current of 4.62 A is passed through a Ni(NO3)2 solution for 1.70 hours. How much nickel is plated out of the solution?
(B) A current of 4.09 A is passed through a Cr(NO3)2 solution. How long (in hours) would this current have to be applied to plate out 7.70 g of chromium?
A)
Electrolysis equation is:
Ni2+ + 2e- ------> Ni
1 mol of Ni requires 2 mol of electron
1 mol of electron = 96485 C
So,1 mol of Ni requires 192970 C
let us calculate the charge passed:
t = 1.7 hr = 1.7*3600 s = 6.12*10^3 s
time, t = 6.12*10^3s
Q = I*t
= 4.62A * 6.12*10^3s
= 2.827*10^4 C
mol of Ni plated = 2.827*10^4/192970 = 0.1465 mol
Molar mass of Ni = 58.69 g/mol
mass of Ni = number of mol * molar mass
= 0.1465 * 58.69
= 8.60 g
Answer: 8.60 g
B)
Electrolysis equation is:
Cr2+ + 2e- ------> Cr
1 mol of Cr requires 2 mol of electron
1 mol of electron = 96485 C
So,1 mol of Cr requires 192970 C
let us calculate mol of element deposited:
use:
number of mol, n = mass/molar mass
= 7.7/52
= 0.1481 mol
total charge = mol of element deposited * charge required for 1 mol
= 0.1481*1.93*10^5
= 2.857*10^4 C
use:
time = Q/i
= 2.857*10^4/4.09
= 6.986*10^3 seconds
= 6.986*10^3/3600 hr
= 1.941 hr
Answer: 1.94 hr