Question

± Analysis of Electroplating 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)

19/20 MC Part A What mass of Cu(s) is electroplated by running 11.5 A of current through a Cu2+(aq) solution for 4.00 h? Express your answer to three significant figures and include the appropriate units. Hints SubmitMy AnswersGive Up Part B How many minutes will it take to electroplate 28.1 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. Hints

Answer 1

Part A

1 mole of Cu²⁺ ions require 2 moles of electrons to get reduced

Q = I. t

where Q is charge in coulombs , I is current in Amperes and t is time in seconds

So putting all the values , we get ,

Q = 11.5 x 4.00 x 60 x 60

Q = 165600 C

Number of moles of electrons will be = 165600 / 96485

= 1.72 moles

1.72 moles of electrons will reduce = 1.72 / 2 = 0.86 moles of copper ions

Molar mass of copper = 63.546 g/mol

So the mass of copper deposited = 0.86 x 63.546

= 54.6 grams

Part B :

1 mole of electrons are required to reduce Au⁺

28.1 g of gold = 28.1 / 196.97 = 0.143 moles

0.143 moles of gold will require equal amount of electrons , that would require a charge of =

0.143 x 96485 = 13797 C

Q = I. t

13797 = 5.00 x t

t = 2759.4 seconds

or 45.9 minutes