Pre-Lab Questions 1. What is the value of the Faraday? 2. What is the value of t

Question

Pre-Lab Questions 1. What is the value of the Faraday? 2. What is the value of the Avogadro's number? 3. What is the charge in Coulombs of a single electron? 4. If a current of 0.75 A is passed through a solution of copper(II) ions for 25 minutes. How many coulombs of charge were passed? How many moles of copper(II) ions should have been reduced to copper metal as a result of passing this electricity through the solution? How many grams of copper metal should have been deposited at the surface of the electrode?

Explanation / Answer

Q1

1 farady is the charge of 1 mol of electrons

so

1 F = 96500 Couloumbs

Q2

Avogrados number is given by :

Na = 6.022*10^23

Q3

charge of 1 e- in C

1 mol of e- = 96500 C

1 mol of e- = 6.022*10^23 e-

then

charge ofe - = 96500 /(6.022*10^23) = 1.6024*10^-19 C/e-

Q4

I = 0.75 A = 0.75 C/s

Cu2+ + 2e- = Cu(s)

t = 25 min = 25*60 s = 1500 s

find C:

C = I*t = 0.75*1500 = 1125 C

mol of e- --_>

1125 /96500 = 0.01165 mol of e-

mol of Cu2´+ = 1/2 mol of e- = 0.01165/2 = 0.005825 mol of Cu

mass of Cu(s) = mol*MW = 0.005825*63.5 = 0.36988 g of Cu

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