lab 9 post lab

# lab 9 post lab - Cu(NH 3 4 2 Cu 2 4NH 3 initial.0083 M M.47...

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During the lab, we assumed that the complexation reaction between Cu 2+ and NH 3 went to completion. Let's check that assumption. Assuming that you used 5.00 mL of 0.010 M Cu(NO 3 ) 2 and 1.00 mL of 3.0 M NH 3 AND that the reaction goes to completion, please complete the following reaction table. Cu 2+ + 4NH 3 Cu(NH 3 ) 4 2+ K f = 4.8 x 10 12 initial .0083 M .50 M 0 M -.0083 M -.033 M +.0083 M final 0 M .47 M .0083 M Now consider the reverse reaction, Cu(NH 3 ) 4 2+ Cu 2+ + 4NH 3 What is the equilibrium constant for this reaction? 2.1e-13 Begining with the "final" concentrations from the table above AND taking equilibrium into account this time, please complete the following reaction table.

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Unformatted text preview: Cu(NH 3 ) 4 2+ Cu 2+ + 4NH 3 initial .0083 M M .47 M-3.6e-14 M +3.6e-14 M 1.5e-13 M equilibrium .0083 M 3.6e-14 M .47 M What percentage of the original Cu 2+ is still present as free Cu 2+ after addition of the NH 3 ? 4.4e-10 % So, how good was the original assumption that all the Cu 2+ would be present as Cu(NH 3 ) 4 2+ ? The assumption was poor but it made the calculations easier. The assumption was ok and should not affect the results. The assumption was very good! This does not indicate how good the assumption was; more tests are needed....
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## This note was uploaded on 03/18/2011 for the course CHEM 202 taught by Professor Feducia during the Spring '09 term at N.C. State.

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lab 9 post lab - Cu(NH 3 4 2 Cu 2 4NH 3 initial.0083 M M.47...

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