Chapter 15

Consider the complex ion \(\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2} \mathrm{Cl}_{2}(\mathrm{OH})_{2}\right]^{2-}\). (a) Identify the ligands and their charges. (b) What is the oxidation number of nickel? (c) What is the formula for the sodium salt of this ion?

Consider the complex ion \(\left[\mathrm{Co}(\mathrm{en})_{2}(\mathrm{SCN}) \mathrm{Cl}\right]^{+} .\) (a) Identify the ligands and their charges. (b) What is the oxidation number of cobalt? (c) What is the formula for the sulfide salt of this ion?

Chromium(III) forms many complexes, among them those with the following ligands. Give the formula and charge of each chromium complex ion described below. (a) two oxalate ions \(\left(\mathrm{C}_{2} \mathrm{O}_{4}{\underline{\phantom{xx}}}^{2-}\right)\) and two water molecules (b) five ammonia molecules and one sulfate ion (c) one ethylenediamine molecule, two ammonia molecules, and two iodide ions

WEB Platinum(II) forms many complexes, among them those with the following ligands. Give the formula and charge of each complex. (a) two ammonia molecules and one oxalate ion \(\left(\mathrm{C}_{2} \mathrm{O}_{4}{\underline{\phantom{xx}}}^{2-}\right)\) (b) two ammonia molecules, one thiocyanate ion \(\left(\mathrm{SCN}^{-}\right)\), and one bromide ion (c) one ethylenediamine molecule and two nitrite ions

What is the coordination number of the metal in the following complexes? (a) \(\left[\mathrm{Mo}(\mathrm{CNS})_{2}(e n)_{2}\right]^{+}\) (b) \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)(\mathrm{OH})_{2} \mathrm{Br}\right]^{-}\) (c) \(\left[\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}\right]^{+}\) (d) \(\left[\mathrm{PtCl}_{2}\left(\mathrm{NO}_{2}\right)_{2}\right]^{2-}\)

What is the coordination number of the metal in the following complexes? (a) \(\left[\mathrm{Mn}\left(\mathrm{NH}_{3}\right)_{2}(\mathrm{OH})_{\mathrm{A}}\right]^{2+}\) (b) \(\left[\mathrm{CuCl}_{4}\right]^{3-}\) (c) \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{ox})_{2}\right]^{2-}\) (d) \(\left[\mathrm{Au}(\mathrm{CN})_{2}\right]^{+}\)

What is the mass percent of nitrogen in the \(\mathrm{Co}(\mathrm{en})_{3}{\underline{\phantom{xx}}}^{3+}\) complex ion?

What is the mass percent of chromium in the chloride salt of \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5}(\mathrm{OH})\right]^{2+} ?\)

There are four iron atoms in each hemoglobin molecule. The mass percent of iron in a hemoglobin molecule is \(0.35 \%\). Estimate the molar mass of hemoglobin.

Vitamin \(\mathrm{B}_{12}\) is a coordination compound with cobalt as its central atom. It contains \(4.4 \%\) cobalt by mass and has a molar mass of \(1.3 \times\) \(10^{3} \mathrm{~g} / \mathrm{mol}\). How many cobalt atoms are in a molecule of vitamin \(\mathrm{B}_{12} ?\)

Sketch the geometry of (a) \(\left[\mathrm{Zn}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\right]\) (tetrahedral) (b) cis \(-\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}\right]^{+}\) (c) trans- \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Br}_{2}\right]^{2+}\) (d) trans- \(\left[\mathrm{Ni}(\mathrm{ox})_{2}(\mathrm{OH})_{2}\right]^{3-}\) (e) \([\mathrm{Au}(\mathrm{CN}) \mathrm{Br}]^{+}\)

Which of the following octahedral complexes show geometric isomerism? If geometric isomers are possible, draw their structures. (a) \(\left[\mathrm{Co}(e n) \mathrm{Cl}_{4}\right]^{-}\) (b) \(\left[\mathrm{Ni}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2} \mathrm{ClBr}\right]^{4-}\) (c) \(\left[\mathrm{Cd}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{4}\right]^{2-}\)

Draw all the structural formulas for the octahedral complexes of \(\mathrm{Co}^{3+}\) with only ox and/or \(\mathrm{NH}_{3}\) as ligands.

Give the electronic configuration for (a) \(\mathrm{Ti}^{3+}\) (b) \(\mathrm{Cr}^{2+}\) (c) \(\mathrm{Ru}^{4+}\) (d) \(\mathrm{Pd}^{2+}\) (e) \(\mathrm{Mo}^{3+}\)

Give the electronic configuration for (a) \(\mathrm{Fe}^{3+}\) (b) \(\mathrm{V}^{2+}\) (c) \(\mathrm{Zn}^{2+}\) (d) \(\mathrm{Cu}^{+}\) (e) \(\mathrm{Mn}^{4+}\)

Give the electron distribution in low-spin and/or high-spin complexes of (a) \(\mathrm{Ru}^{4+}\) (b) \(\mathrm{Pt}^{2+}\)

Follow the directions of Question 29 for (a) \(\mathrm{Mo}^{3+}\) (b) \(\mathrm{Pd}^{4+}\)

. For complexes of \(\mathrm{V}^{3+}\), only one distribution of electrons is possible. Explain.

Explain why \(\mathrm{Mn}^{3+}\) forms high-spin and low-spin octahedral complexes but \(\mathrm{Mn}^{4+}\) does not.

[ \(\left[\mathrm{Cr}(\mathrm{CN})_{6}\right]^{4-}\) is less paramagnetic than \(\left[\mathrm{Cr}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}\). Explain.

Why is \(\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{6}\right]^{3+}\) diamagnetic while \(\left[\mathrm{CoF}_{6}\right]^{3-}\) is paramagnetic?

Give the number of unpaired electrons in octahedral complexes with strong- field ligands for (a) \(\mathrm{Rh}^{3+}\) (b) \(\mathrm{Mn}^{3+}\) (c) \(\mathrm{Ag}^{+}\) (d) \(\mathrm{Pt}^{4+}\) (e) \(\mathrm{Au}^{3+}\)

\(\mathrm{Ti}\left(\mathrm{NH}_{3}\right)_{6}{\underline{\phantom{xx}}}^{3+}\) has a d-orbital electron transition at \(399 \mathrm{~nm}\). Find \(\Delta_{o}\) at this wavelength.

\(\mathrm{MnF}_{6}{\underline{\phantom{xx}}}^{2-}\) has a crystal field splitting energy, \(\Delta_{0}\) of \(2.60 \times 10^{2} \mathrm{~kJ} / \mathrm{mol}\). What is the wavelength responsible for this energy?

The wavelength of maximum absorption of \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\) is \(580 \mathrm{~nm}\) (orange-yellow). What color is a solution of \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+} ?\)

At what concentration of cyanide ion is (a) \(\left[\mathrm{Cd}^{2+}\right]=10^{-8} \times\left[\mathrm{Cd}(\mathrm{CN})_{4}^{2-}\right] ?\) (b) \(\left[\mathrm{Fe}^{2+}\right]=10^{-20} \times\left[\mathrm{Fe}(\mathrm{CN})_{6}{\underline{\phantom{xx}}}^{4-}\right] ?\)

Consider the complex ion \(\left[\mathrm{Ni}(\mathrm{en})_{3}\right]^{2+} .\) Its \(K_{\mathrm{f}}\) is \(2.1 \times 10^{18} .\) At what concentration of \(e n\) is \(67 \%\) of the \(\mathrm{Ni}^{2+}\) converted to \(\left.\left[\mathrm{Ni}(\mathrm{en})_{3}\right]^{2+}\right\\}\)

Analysis of a coordination compound gives the following results: \(22.0 \% \mathrm{Co}, 31.4 \% \mathrm{~N}, 6.78 \% \mathrm{H}\), and \(39.8 \% \mathrm{Cl} .\) One mole of the compound dissociates in water to form four moles of ions. (a) What is the simplest formula of the compound? (b) Write an equation for its dissociation in water.

What are the concentrations of \(\mathrm{Cu}^{2+}, \mathrm{NH}_{3}\), and \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\) at equilibrium when \(18.8 \mathrm{~g}\) of \(\mathrm{Cu}\left(\mathrm{NO}_{3}\right)_{2}\) is added to \(1.0 \mathrm{~L}\) of a \(0.400 \mathrm{M}\) solution of aqueous ammonia? Assume that the reaction goes to completion and forms \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4}^{2+}\).

Oxyhemoglobin is red, and hemoglobin is blue. Use Le Châtelier's principle to explain why venous blood is blue and arterial blood is bright red.

For the system hemoglobin \(\cdot \mathrm{O}_{2}(a q)+\mathrm{CO}(g) \rightleftharpoons\) hemoglobin \(\cdot \mathrm{CO}(a q)+\mathrm{O}_{2}(g)\) \(K=2.0 \times 10^{2} .\) What must be the ratio of \(P_{\mathrm{Co}} / P_{\mathrm{O}_{2}}\) if \(12.0 \%\) of the hemoglobin in the bloodstream is converted to the CO complex?

Bipyridyl (Bipy) is a molecule commonly used as a bidentate ligand. When \(0.17 \mathrm{~mol}\) of bipyridyl is dissolved in \(2.4 \mathrm{~L}\) of a solution that contains \(0.052 \mathrm{M} \mathrm{Fe}^{2+},\left[\mathrm{Fe}(\mathrm{bipy})_{3}\right]^{2+}\left(K_{\mathrm{f}}=1.6 \times 10^{17}\right)\) is formed. What are the con- centrations of all species when equilibrium is established?

Explain why (a) oxalic acid removes rust stains. (b) there are no geometric isomers of tetrahedral complexes. (c) cations such as \(\mathrm{Co}^{2+}\) act as Lewis acids. (d) \(\mathrm{C}_{2} \mathrm{O}_{4}^{2-}\) is a chelating agent. (e) \(\mathrm{NH}_{3}\) can be a ligand but \(\mathrm{NH}_{4}{\underline{\phantom{xx}}}^{+}\) is not.

WEB Indicate whether each of the following is true or false. If the statement is false, correct it. (a) The coordination number of iron(III) in \(\mathrm{Fe}\left(\mathrm{NH}_{3}\right)_{4}(\mathrm{en})^{3+}\) is 5 . (b) \(\mathrm{Ni}(\mathrm{CN})_{6}^{4-}\) is expected to absorb at a longer wavelength than \(\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}{\underline{\phantom{xx}}}^{2+}\)

Consider three complexes of \(\mathrm{Ag}^{+}\) and their formation constants, \(K_{\mathrm{f}}\) $$\begin{array}{ll}\hline \text { Complex lon } & K_{\mathrm{f}} \\\\\hline \mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}+ & 1.6 \times 10^{7} \\ \mathrm{Ag}(\mathrm{CN})_{2}^{-} & 5.6 \times 10^{18} \\\\\mathrm{AgBr}_{2}^{-} & 1.3 \times 10^{7} \\ \hline\end{array}$$ Which statements are true? (a) \(\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}{\underline{\phantom{xx}}}^{+}\) is more stable than \(\mathrm{Ag}(\mathrm{CN})_{2}^{-}\). (b) Adding a strong acid \(\left(\mathrm{HNO}_{3}\right)\) to a solution that is \(0.010 \mathrm{M}\) in \(\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}^{+}\) will tend to dissociate the complex ion into \(\mathrm{Ag}^{+}\) and \(\mathrm{NH}_{4}^{+} .\) (c) Adding a strong acid \(\left(\mathrm{HNO}_{3}\right)\) to a solution that is \(0.010 \mathrm{M}\) in \(\mathrm{AgBr}_{2}^{-}\) will tend to dissociate the complex ion into \(\mathrm{Ag}^{+}\) and \(\mathrm{Br}^{-} .\) (d) To dissolve AgI, one can add either \(\mathrm{NaCN}\) or \(\mathrm{HCN}\) as a source of the cyanide-complexing ligand. Fewer moles of NaCN would be required. (e) Solution \(A\) is \(0.10 M\) in \(B r^{-}\) and contains the complex ion \(\mathrm{AgBr}_{2}^{-}\). Solution B is \(0.10 M\) in \(\mathrm{CN}^{-}\) and contains the complex ion \(\mathrm{Ag}(\mathrm{CN})_{2}-\). Solution B will have more particles of complex ion per particle of \(\mathrm{Ag}^{+}\) than solution \(\mathrm{A}\).

A child eats \(10.0 \mathrm{~g}\) of paint containing \(5.0 \% \mathrm{~Pb}\). How many grams of the sodium salt of EDTA, \(\mathrm{Na}_{4}(\mathrm{EDTA})\), should he receive to bring the lead into solution as \(\mathrm{Pb}\). EDTA?

In the \(\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}{\underline{\phantom{xx}}}^{3+}\) ion, the splitting between the \(\mathrm{d}\) levels, \(\Delta_{\mathrm{o}}\) is \(55 \mathrm{kcal} / \mathrm{mol}\). What is the color of this ion? Assume that the color results from a transition between upper and lower d levels.