Chemistry Principles and Reactions

William L Masterton; Cecile N Hurley; Edward J Neth

Chapter 19

Complex Ions - all with Video Answers

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Chapter Questions

Problem 1

Consider the complex ion $\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2} \mathrm{Cl}_{2}(\mathrm{OH})_{2}^{2-}\right]$
(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?

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Problem 2

Consider the complex ion $\left[\mathrm{Cd}(e n)(\mathrm{SCN})_{2}(\mathrm{OH})_{2}^{-}\right]$
(a) Identify the ligands and their charges.
(b) What is the oxidation number of cadmium?
(c) What is the formula for the magnesium salt of this ion?

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Problem 3

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 $\left(\mathrm{C}_{2} \mathrm{O}_{4}^{2-}\right)$ and two water molecules
(b) five ammonia molecules and one sulfate ion
(c) one ethylenediamine molecule, two ammonia molecules, and two iodide ions

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Problem 4

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 $\left(\mathrm{C}_{2} \mathrm{O}_{4}{ }^{2-}\right)$
(b) two ammonia molecules, one thiocyanate ion $\left(\mathrm{SCN}^{-}\right)$, and one bromide ion
(c) one ethylenediamine molecule and two nitrite ions

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Problem 5

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) $\left[\mathrm{PtCl}_{2}\left(\mathrm{NO}_{2}\right)_{2}^{2-}\right.$

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Problem 6

What is the coordination number of the central metal atom in the following complexes?
(a) $\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}{ }^{3+}\right]$
(b) $\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right) \mathrm{Br}_{3}^{-}\right]$
(c) $\left.[\mathrm{V}(e n)) \mathrm{Cl}_{4}^{2-}\right]$
(d) $\left[\mathrm{Au}(\mathrm{CN})_{2}^{+}\right]$

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Problem 7

What is the oxidation number of the metal atom in the complex ions in Question 5?

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Problem 8

What is the oxidation number of the metal atom in the complex ions in Question $6 ?$

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Problem 9

Write the formula for the phosphate salt (if the complex ion is a cation) or the aluminum salt (if the complex ion is an anion) for the ions in Question $5 .$

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Problem 10

Follow the directions for Question 9 for the complex ions in Question $6 .$

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Problem 11

Refer to Table 19.2 to predict the formula of the complex formed by
(a) $\mathrm{Ag}^{+}$ with $\mathrm{H}_{2} \mathrm{O}$
(b) $\mathrm{Pt}^{2+}$ with $\mathrm{H}_{2} \mathrm{O}$
(c) $\mathrm{Pd}^{2+}$ with $\mathrm{Br}^{-}$
(d) $\mathrm{Fe}^{3+}$ with $\mathrm{C}_{2} \mathrm{O}_{4}^{2-}$

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Problem 12

Refer to Table 19.2 to predict the formula of the complex formed by
(a) $\mathrm{Pt}^{4+}$ with $\mathrm{NH}_{3}$
(b) $\mathrm{Ag}^{+}$ with $\mathrm{CN}^{-}$
(c) $\mathrm{Zn}^{2+}$ with $\mathrm{C}_{2} \mathrm{O}_{4}^{2-}$
(d) $\mathrm{Cd}^{2+}$ with $\mathrm{CN}^{-}$

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Problem 13

What is the mass percent of nitrogen in the $\left[\mathrm{Co}(e n)_{3}^{3+}\right]$ complex ion?

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Problem 14

What is the mass percent of $\mathrm{Cl}$ in the sulfate salt of $\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4} \mathrm{Cl}_{2}^{+}\right] ?$

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Problem 15

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.

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Problem 16

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 $\mathrm{B}_{12}$ ?

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Problem 17

Write formulas for the following ions or compounds:
(a) zinchexachloroplatinate(IV)
(b) dichlorobis(ethylenediamine)nickel(II)
(c) diamminetriaquahydroxochromium(III) nitrate
(d) ammonium pentachlorohydroxyferrate(III)

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Problem 18

Write formulas for the following ions or compounds:
(a) tetraammineaquachlorocobalt(III) chloride
(b) pentaamminesulfatochromium(III) bromide
(c) potassium tetracyanonickelate(II)
(d) pentamminenitratoiron(II)

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Problem 19

Name the following ions or compounds:
(a) $\left[\mathrm{Ru}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{Cl}^{2+}\right]$
(b) $\left[\mathrm{Mn}\left(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\right)_{3}^{2+}\right]$
(c) $\mathrm{K}_{2}\left[\mathrm{PtCl}_{4}\right]$
(d) $\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{5} \mathrm{I}\right] \mathrm{I}_{2}$

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Problem 20

Name the following ions or compounds:
(a) $\mathrm{Na}\left[\mathrm{Al}(\mathrm{OH})_{4}\right]$
(b) $\left[\mathrm{Co}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2}\left(\mathrm{H}_{2} \mathrm{O}_{2}^{-}\right]\right.$
(c) $\left[\operatorname{Ir}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Cl}_{3}\right]$
(d) $\left[\mathrm{Cr}(\mathrm{en})\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Br}_{2}\right]_{2} \mathrm{SO}_{4}$

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Problem 21

Name the compounds or ions in Question $5 .$

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Problem 22

Name the compounds or ions in Question $6 .$

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Problem 23

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) $[\mathrm{Au}(\mathrm{CN}) \mathrm{Br}]^{+}$

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Problem 24

Sketch the geometry of
(a) $\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2} \mathrm{I}_{2}\right]$ (tetrahedral)
(b) $\left[\mathrm{Ag}(\mathrm{SCN})_{2}^{-}\right]$
(c) $\mathrm{cis}-\left[\mathrm{Ni}(\mathrm{OH})_{2} \mathrm{Cl}_{2}^{-}\right]$
(d) trans- $\left[\mathrm{Cr}(e n)_{2}\left(\mathrm{NH}_{3}\right)_{2}^{3+}\right]$
(e) cis-[Co $\left.(o x)\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}{ }^{+}\right]$

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Problem 25

The compound 1,2-diaminocyclohexane
(abbreviated "dech") is a ligand in the promising anticancer complex cis $-\mathrm{Pd}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}(\mathrm{dech})^{2+}$. Sketch the geometry of this complex.

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Problem 26

The acetylacetonate ion (acac $\left.^{-}\right)$
forms complexes with many metal ions. Sketch the geometry of $\mathrm{Fe}(\mathrm{acac})_{3} .$

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Problem 27

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) $\left[\mathrm{Ni}\left(\mathrm{C}_{2} \mathrm{O}_{4}\right)_{2} \mathrm{ClBr}^{4-}\right]$
(c) $\left[\mathrm{Cd}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{4}^{2-}\right]$

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Problem 28

Follow the directions of Question 27 for the following.
(a) $\left[\mathrm{Cr}\left(\mathrm{NH}_{3}\right)_{2}(\mathrm{SCN})_{4}{ }^{2-}\right]$
(b) $\left[\mathrm{Co}\left(\mathrm{NH}_{3}\right)_{3}\left(\mathrm{NO}_{2}\right)_{3}^{-}\right]$
(c) $\left[\mathrm{Mn}\left(\mathrm{H}_{2} \mathrm{O}\right)_{2}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{OH}^{+}\right]$

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Problem 29

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

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Problem 30

Draw all the structural formulas for the octahedral complexes of $\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{3}(\mathrm{OH})_{2} \mathrm{Cl}\right] .$

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Problem 31

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

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Problem 32

Give the electronic configuration for
(a) $\mathrm{Cd}^{2+}$
(b) $\mathrm{Fe}^{2+}$
(c) $\mathrm{Pt}^{2+}$
(d) $\mathrm{Mn}^{2+}$
(e) $\mathrm{Ni}^{3+}$

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Problem 33

Write an abbreviated orbital diagram and determine the number of unpaired electrons in each species in Question 31 .

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Problem 34

Write an abbreviated orbital diagram and determine the number of unpaired electrons in each species in Question 32 .

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Problem 35

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

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Problem 36

Follow the directions of Question 35 for
(a) $\mathrm{Fe}^{2+}$
(b) $\mathrm{Mn}^{3+}$

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Problem 37

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

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Problem 38

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

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Problem 39

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

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Problem 40

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

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Problem 41

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) $\mathrm{Au}^{3+}$

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Problem 42

For the species in Question 41 , indicate the number of unpaired electrons with weak-field ligands.

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Problem 43

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

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Problem 44

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

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Problem 45

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

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Problem 46

A solution of $\left[\mathrm{Fe}(\mathrm{CN})_{6}^{3-}\right]$ appears red. Using Figure $19.11,$ estimate the wavelength of maximum absorption.

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Problem 47

A chemist synthesizes two coordination compounds. One compound decomposes at $280^{\circ} \mathrm{C},$ the other at $240^{\circ} \mathrm{C}$. Analysis of the compounds gives the same mass percent data: $52.6 \% \mathrm{Pt}, 7.6 \% \mathrm{~N}, 1.63 \% \mathrm{H},$ and $38.2 \%$ Cl. Both
compounds contain a +4 central ion.
(a) What is the simplest formula of the compounds?
(b) Draw structural formulas for the complexes present.

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Problem 48

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.

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Problem 49

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 $\mathrm{NH}_{4}^{+}$ is not.

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Problem 50

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 $\left[\mathrm{Fe}\left(\mathrm{NH}_{3}\right)_{4}(e n)^{3+}\right]$ is 5 .
(b) $\left[\mathrm{Ni}(\mathrm{CN})_{6}{ }^{4-}\right]$ is expected to absorb at a longer wavelength than $\left[\mathrm{Ni}\left(\mathrm{NH}_{3}\right)_{6}^{2+}\right]$
(c) Complexes of $\mathrm{Cr}^{3+}$ are brightly colored, and those of $\mathrm{Zn}^{2+}$ are colorless.
(d) Ions with seven or more d electrons cannot form both high- and low-spin octahedral complexes.

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Problem 51

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 $\mathrm{Pb}$ \cdot EDTA?

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Problem 52

A certain coordination compound has the simplest formula $\mathrm{PtN}_{2} \mathrm{H}_{6} \mathrm{Cl}_{2}$. It has a molar mass of about $600 \mathrm{~g} / \mathrm{mol}$ and contains both a complex cation and a complex anion. What is its structure?

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Problem 53

Two coordination compounds decompose at different temperatures but have the same mass percent analysis data: $20.25 \%$ Cu, $15.29 \%$ C, $7.07 \% \mathrm{H}, 26.86 \% \mathrm{~N}, 10.23 \% \mathrm{~S},$ and $20.39 \%$ O. Each contains $\mathrm{Cu}^{2+}$
(a) Determine the simplest formula of the compounds.
(b) Draw the structural formulas of the complex ion in each case.

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Problem 54

In the $\left[\mathrm{Ti}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}{ }^{3+}\right]$ ion, the splitting between the $\mathrm{d}$ levels, $\Delta_{0}$, 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.

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