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 contain such as Ag^+, the flow of electrons veil 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 1 ampere (A) = 1 coulomb/second (C/s) What mass of Cu(s) is electroplated by running 12 5 A of current through a Cu^2+ (aq) solution for 4.00 h? Express your answer to three significant figures and include the appropriate units. How many minutes will it take to electroplate 23.1 g of gold by running 5.00 A of current through a solution of Au^+ (aq)? Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

A)

Cu2+ and 2e- --> Cu(s)

then we need 2 mol of e- per mol of Cu

MW of Cu = 63.5 g/mol

if I = 12.5 A and t = 4 hr = 14400 s then

Charge = I*t = 12.5*14400 = 180000 C

find moles using faradays constant

mol e - = C/F = 180000/96500 = 1.8652 mol of e-

then 1.8652/2 mol of Cu = 0.9326 mol of Cu are produced

mass = mol*MW = 0.9326*63.4= 59.126 g of Cu

b)

m = 23.1 g of Au

Au+3 + 3e- --> Au(s)

I = 5 A

time needed? find total charge

mol = mass/MW = 23.1 /196.96657 = 0.117278 mol of e-

we require 3 mol of e- per mol of Au so

3*0.117278= 0.351834 mol of e-

find total chargee

C = F*mol = 96500*0.351834 = 33951.981 C

Since I = C/t

t = C/I = 33951.981/5 = 6790.3962 s = 113.17327 minutes

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