When electricity (the flow of electrons) is passed through a solution, it causes

Question

When electricity (the flow of electrons) is passed through a solution, it causes an oxidation-reduction (redox) reaction to occur. If the solution contains a metal cation such as Ag+, the flow of electrons will reduce the silver ion, causing solid silver to plate onto the electrode. The amount of metal plated depends on the number of electrons passed. The total charge of a mole of electrons is 96,485 coulombs (C) and 1ampere(A)=1coulomb/second(C/s)

a) What mass of Cu(s) is electroplated by running 18.0 A of current through a Cu2+(aq) solution for 4.00 h?

b) How many minutes will it take to electroplate 54.1 g of gold by running 5.00 A of current through a solution of Au+(aq)?

Explanation / Answer

a)
Electrolysis equation is:
Cu2+   +   2e-    ------> Cu

1 mol of Cu requires 2 mol of electron
1 mol of electron = 96485 C
So,1 mol of Cu requires 192970 C

let us calculate the charge passed:
t = 4.0 hr = 4.0*3600 s = 14400 s

time, t = 14400s

Q = I*t
= 18A * 14400s
= 259200 C

mol of Cu plated = 259200/192970 = 1.34321 mol
Molar mass of Cu = 63.55 g/mol

mass of Cu = number of mol * molar mass
= 1.34321 * 63.55
= 85.36125g

Answer: 85.4 g

b)
Electrolysis equation is:
Au1+   +   1e-    ------> Au

1 mol of Au requires 1 mol of electron
1 mol of electron = 96485 C
So,1 mol of Au requires 96485 C

let us calculate mol of element deposited:
use:
number of mol, n = mass/molar mass
= 54.1/197
= 0.27462 mol


total charge = mol of element deposited * charge required for 1 mol
= 0.27462*96485
= 26496.6421 C
use:
time = Q/i
= 26496.6421/5
= 5299.3284 seconds
= 5299.3284/60 min
= 88 minutes
Answer: 88 minutes

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