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)

What mass of Cu(s) is electroplated by running 27.5 A of current through a Cu2+(aq) solution for 4.00 h?

How many minutes will it take to electroplate 10.1 g of gold by running 5.00 A of current through a solution of Au+(aq)?

Explanation / Answer

solution:

1)
Cu2+(aq) + 2e –> Cu(s)

The charge can be calculated as = current X time = 27.5 X 1.44 X 60 X 60

27.5 A X 1.44 x 10^4 s = 3.96 x 10^5 C

We know that 96,485 coulombs = 1 Faraday

so 3.96 x 10^5 C will be equal to = 3.96 x 10^5 / 96485 Faraday = 4.104 Faraday

1 Faraday will reduce 1/2 mole of Copper

so 4.104 farady will reduce = 4.104 / 2 moles of copper = 2.052 moles

1 moles of copper = 63.5 g / moles

so copper electroplated = 2.052 moles = 2.052 X 63.5 grams = 130.302 grams


2) the reaction will be

Au+ + e –> Au(s)
moles of Gold electroplated = mass / atomic weight of gold = 10.1 / 197 = 0.0512 moles
1 moles will be produced by 96485 coloumbs

so 0.0521 moles will be produced by = 0.0521 X 96485 coloumbs = 5026.86 coloumbs
current = 5 ampere

current = charge / time

So time = charge / current = 5026.86 / 5 = 1005.37 seconds = 16.75 minutes

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