17.5.1 The Formation of Complex Ions

Question 1

When the cobalt cation, Co2+, reacts with water, H2O, a Lewis acid-Lewis base reaction occurs, resulting in the product, Co(H2O)62+.
Co(H2O)62+ can then combine with Cl − to form CoCl42− in another Lewis acid-Lewis base reaction.

Co(H2O)6^2+(aq) + 4Cl^-(aq) CoCl4^2-(aq) + 6H2O(l)

Which statement about this reaction, that results in the formation of CoCl42−, is not correct?

Answer 1

When the Co2+ is first dissolved in water at the start of the process, it functions as a non-complex ion.

Question 2

Let’s examine the reaction of Cu2+ and NH3 from the lesson,

Cu2+(aq) + 4NH3(aq) Cu(NH3)4^2+(aq)

where Kf  = 4.8 × 1012.
Suppose that we have 750 mL of total solution. There is 0.55 M NH3 in solution. We slowly add 0.22 moles of copper sulfate (which yields the Cu2+ metal cation). What is the limiting reagent in this reaction?

Answer 2

NH3

Question 3

Look at the reaction of Cu2+ and NH3,

Cu2+(aq) + 4NH3(aq) Cu(NH3)4^2+(aq)

where Kf = 4.8 × 1012.

Suppose that we have 800 mL of total solution. There are 0.85 M NH3 in solution. We slowly add 0.15 moles of copper sulfate (which yields the Cu2+ metal cation). If Cu2+ is the limiting reagent, what are the final equilibrium concentrations for NH3 and Cu(NH3 )42+?

Answer 3

[ NH3 ] = 0.1 mol / L;
[Cu(NH3 )42+ ] = 0.19 mol / L

Question 4

Look at the reaction of Cu2+ and NH3,

Cu2+(aq) + 4NH3(aq) Cu(NH3)4^2+(aq)

where Kf = 4.8 × 1012.
Suppose that we have 850 mL of total solution. There are 0.78 M NH3 in solution. We slowly add 0.14 moles of copper sulfate. What is the final equilibrium concentration of Cu2+, the limiting reagent?

Answer 4

1.6 × 10−10 mol / L

Question 5

Which of the following best defines a complex ion?

Answer 5

a charged compound formed from a metal ion and other ions or molecules

Question 6

Which of the following is not a complex ion?

Answer 6

Ba2+

Question 7

Which of the following statements about metal ions dissolved in water is not correct?

Answer 7

All metal anions are complex ions when they are dissolved in water.

Question 8

When the cobalt cation, Co2+, reacts with water, H2O, a Lewis acid-Lewis base reaction occurs.

Co2+(aq) + 6H2O(l) Co(H2O)6^2+(aq)

Which statement about this reaction is not correct?

Answer 8

The overall charge on the cobalt ion is different from the overall charge on the complex ion.

Question 9

A ligand is a ______________

Answer 9

molecule or ion that binds to a metal ion by donating a pair of electrons.

Question 10

Which statement best defines the formation constant, Kf ?

Answer 10

Kf is the equilibrium constant for the reaction in which a complex ion is formed from a metal cation and one or more ligands.