1 st you need the BALANCED EQUATION

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# 1 st you need the BALANCED EQUATION - PowerPoint PPT Presentation

1 st you need the BALANCED EQUATION. Pb 2+ + 2 e- Pb (s) E 0 red = -0.13 V Cu 2+ + 2 e- Cu (s) E 0 red = 0.34 V You need an OXIDATION and a REDUCTION. E 0 cell &gt;0 or nothing happens!. 1 st you need the BALANCED EQUATION. Pb (s)  Pb 2+ + 2 e- E 0 ox = + 0.13 V

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Presentation Transcript
1st you need the BALANCED EQUATION

Pb2+ + 2 e- Pb(s)E0red = -0.13 V

Cu2+ + 2 e- Cu(s) E0red = 0.34 V

You need an OXIDATION and a REDUCTION.

E0cell >0 or nothing happens!

1st you need the BALANCED EQUATION

Pb(s)Pb2+ + 2 e- E0ox = +0.13 V

Cu2+ + 2 e- Cu(s) E0red = 0.34 V

Pb(s) + Cu2+ Pb2+ + Cu(s) E0cell = 0.13+0.34V

That assumes 1 M concentrations.

Since they aren’t 1 M: NERNST EQUATION

1st you need the BALANCED EQUATION

Pb(s) + Cu2+ Pb2+ + Cu(s) E0cell = 0.47 v

Ecell = E0cell – 0.0592/n log Q

Ecell = E0cell – 0.0592 log Pb2+

n Cu2+

Ecell = 0.47V – 0.0592 log 0.050

2 1.50

Ecell = 0.51 V

What is the cell potential when the concentration of Cu2+ has fallen to 0.200 M?

Ecell = E0cell – 0.0592 log Pb2+

n Cu2+

Ecell = 0.47V – 0.0592 log 1.35

2 0.2

Ecell = 0.45 V

Pb(s) + Cu2+ Pb2+ + Cu(s)

What are the concentrations of Pb2+ and Cu2+ when the cell potential falls to 0.35 V?

Ecell = E0cell – 0.0592 log Pb2+

n Cu2+

0.35 = 0.47V – 0.0592 log 0.05+x

2 1.5-x

-0.12 = -0.0296 log (0.05+x/1.5-x)

4.054 = log (0.05+x/1.5-x)

104.054= 0.05+x/1.5-x

1.1324x104 = 0.05+x/1.5-x

1.6986x104 – 1.1324x104 x = 0.05 +x

1.6986x104 = 1.1325x104 x

X = 1.4999

Pb(s) + Cu2+ Pb2+ + Cu(s)

What are the concentrations of Pb2+ and Cu2+ when the cell potential falls to 0.35 V?

Ecell = E0cell – 0.0592 log Pb2+

n Cu2+

0.35 = 0.47V – 0.0592 log 0.05+x

2 1.5-x

-0.12 = -0.0296 log (0.05+x/1.5-x)

4.054 = log (0.05+x/1.5-x)

104.054= 0.05+x/1.5-x

1.1324x104 = 0.05+x/1.5-x

1.6986x104 – 1.1324x104 x = 0.05 +x

1.6986x104 = 1.1325x104 x

X = 1.4999

Pb(s) + Cu2+ Pb2+ + Cu(s)

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