Answer: Aqueous solutions of CoCl2 are generally either

What distinguishes a transition metal from a representative metal?

Why is zinc not considered a transition metal?

Explain why atomic radii decrease very gradually from scandium to copper.

Without referring to the text, write the ground-state electron configurations of the first-row transition metals. Explain any irregularities

Write the electron configurations of the following ions: V51, Cr31, Mn21, Fe31, Cu21, Sc31, Ti41.

Why do transition metals have more oxidation states than other elements?

Give the highest oxidation states for scandium to copper.

Why does chromium seem to be less reactive than its standard reduction potential suggests?

Define the following terms: coordination compound, ligand, donor atom, coordination number, chelating agent

Describe the interaction between a donor atom and a metal atom in terms of a Lewis acid-base reaction.

Complete the following statements for the complex ion [Co(en)2(H2O)CN]21. (a) en is the abbreviation for . (b) The oxidation number of Co is . (c) The coordination number of Co is . (d) is a bidentate ligand.

Complete the following statements for the complex ion [Cr(C2O4)2(H2O)2] 2. (a) The oxidation number of Cr is . (b) The coordination number of Cr is . (c) is a bidentate ligand.

Give the oxidation numbers of the metals in the following species: (a) K3[Fe(CN)6], (b) K3[Cr(C2O4)3], (c) [Ni(CN)4] 22.

Give the oxidation numbers of the metals in the following species: (a) Na2MoO4, (b) MgWO4, (c) Fe(CO)5.

What are the systematic names for the following ions and compounds? (a) [Co(NH3)4Cl2] 1 (c) [Co(en)2Br2] 1 (b) Cr(NH3)3Cl3 (d) [Co(NH3)6]Cl3

What are the systematic names for the following ion and compounds? (a) [cis-Co(en)2Cl2] 1 (b) [Pt(NH3)5Cl]Cl3 (c) [Co(NH3)5Cl]Cl2

Write the formulas for each of the following ions and compounds: (a) tetrahydroxozincate(II), (b) pentaaquachlorochromium(III) chloride, (c) tetrabromocuprate(II), (d) ethylenediaminetetraacetat oferrate(II).

Write the formulas for each of the following ions and compounds: (a) bis(ethylenediamine)- dichlorochromium(III), (b) pentacarbonyliron(0), (c) potassium tetracyanocuprate(II), (d) tetraammineaquachlorocobalt(III) chloride.

Define the following terms: stereoisomers, geometric isomers, optical isomers, plane-polarized light

Specify which of the following structures can exhibit geometric isomerism: (a) linear, (b) square-planar, (c) tetrahedral, (d) octahedral.

What determines whether a molecule is chiral? How does a polarimeter measure the chirality of a molecule?

Explain the following terms: (a) enantiomers, (b) racemic mixtures.

The complex ion [Ni(CN)2Br2] 22 has a square-planar geometry. Draw the structures of the geometric isomers of this complex.

How many geometric isomers are in the following species? (a) [Co(NH3)2Cl4] 2, (b) [Co(NH3)3Cl3]

Draw structures of all the geometric and optical isomers of each of the following cobalt complexes: (a) [Co(NH3)6] 31 (b) [Co(NH3)5Cl]21 (c) [Co(C2O4)3] 32

Draw structures of all the geometric and optical isomers of each of the following cobalt complexes: (a) [Co(NH3)4Cl2] 1, (b) [Co(en)3] 31

Briefly describe crystal field theory

Define the following terms: crystal field splitting, high-spin complex, low-spin complex, spectrochemical series.

What is the origin of color in a coordination compound?

Compounds containing the Sc31 ion are colorless, whereas those containing the Ti31 ion are colored. Explain.

What factors determine whether a given complex will be diamagnetic or paramagnetic?

For the same type of ligands, explain why the crystal field splitting for an octahedral complex is always greater than that for a tetrahedral complex.

The [Ni(CN)4] 22 ion, which has a square-planar geometry, is diamagnetic, whereas the [NiCl4] 22 ion, which has a tetrahedral geometry, is paramagnetic. Show the crystal field splitting diagrams for those two complexes.

Transition metal complexes containing CN2 ligands are often yellow in color, whereas those containing H2O ligands are often green or blue. Explain.

Predict the number of unpaired electrons in the following complex ions: (a) [Cr(CN)6] 42, (b) [Cr(H2O)6] 21.

The absorption maximum for the complex ion [Co(NH3)6] 31 occurs at 470 nm. (a) Predict the color of the complex and (b) calculate the crystal field splitting in kJ/mol.

From each of the following pairs, choose the complex that absorbs light at a longer wavelength: (a) [Co(NH3)6] 21, [Co(H2O)6] 21; (b) [FeF6] 32, [Fe(CN)6] 32; (c) [Cu(NH3)4] 21, [CuCl4] 22.

A solution made by dissolving 0.875 g of Co(NH3)4Cl3 in 25.0 g of water freezes at 20.568C. Calculate the number of moles of ions produced when 1 mole of Co(NH3)4Cl3 is dissolved in water and suggest a structure for the complex ion present in this compound.

Define the terms (a) labile complex, (b) inert complex

Explain why a thermodynamically stable species may be chemically reactive and a thermodynamically unstable species may be unreactive.

Oxalic acid, H2C2O4, is sometimes used to clean rust stains from sinks and bathtubs. Explain the chemistry underlying this cleaning action

The [Fe(CN)6] 32 complex is more labile than the [Fe(CN)6] 42 complex. Suggest an experiment that would prove that [Fe(CN)6] 32 is a labile complex.

Aqueous copper(II) sulfate solution is blue in color. When aqueous potassium fluoride is added, a green precipitate is formed. When aqueous potassium chloride is added instead, a bright-green solution is formed. Explain what is happening in these two cases.

When aqueous potassium cyanide is added to a solution of copper(II) sulfate, a white precipitate, soluble in an excess of potassium cyanide, is formed. No precipitate is formed when hydrogen sulfide is bubbled through the solution at this point. Explain.

A concentrated aqueous copper(II) chloride solution is bright green in color. When diluted with water, the solution becomes light blue. Explain.

In a dilute nitric acid solution, Fe31 reacts with thiocyanate ion (SCN2) to form a dark-red complex: [Fe(H2O)6] 31 1 SCN2 H2O 1 [Fe(H2O)5NCS]21 The equilibrium concentration of [Fe(H2O)5NCS]21 may be determined by how darkly colored the solution is (measured by a spectrometer). In one such experiment, 1.0 mL of 0.20 M Fe(NO3)3 was mixed with 1.0 mL of 1.0 3 1023 M KSCN and 8.0 mL of dilute HNO3. The color of the solution quantitatively indicated that the [Fe(H2O)5NCS]21 concentration was 7.3 3 1025 M. Calculate the formation constant for [Fe(H2O)5NCS]21.

As we read across the first-row transition metals from left to right, the 12 oxidation state becomes more stable in comparison with the 13 state. Why is this so?

Which is a stronger oxidizing agent in aqueous solution, Mn31 or Cr31? Explain your choice.

Carbon monoxide binds to Fe in hemoglobin some 200 times more strongly than oxygen. This is the reason why CO is a toxic substance. The metal-toligand sigma bond is formed by donating a lone pair from the donor atom to an empty sp3 d2 orbital on Fe. (a) On the basis of electronegativities, would you expect the C or O atom to form the bond to Fe? (b) Draw a diagram illustrating the overlap of the orbitals involved in the bonding

What are the oxidation states of Fe and Ti in the ore ilmenite, FeTiO3? (Hint: Look up the ionization energies of Fe and Ti in Table 23.1; the fourth ionization energy of Ti is 4180 kJ/mol.)

A student has prepared a cobalt complex that has one of the following three structures: [Co(NH3)6]Cl3, [Co(NH3)5Cl]Cl2, or [Co(NH3)4Cl2]Cl. Explain how the student would distinguish between these possibilities by an electrical conductance experiment.At the students disposal are three strong electrolytesNaCl, MgCl2, and FeCl3which maybe used for comparison purposes

Chemical analysis shows that hemoglobin contains 0.34 percent of Fe by mass. What is the minimum possible molar mass of hemoglobin? The actual molar mass of hemoglobin is about 65,000 g. How do you account for the discrepancy between your minimum value and the actual value?

Explain the following facts: (a) Copper and iron have several oxidation states, whereas zinc has only one. (b) Copper and iron form colored ions, whereas zinc does not.

A student in 1895 prepared three coordination compounds containing chromium, with the following properties: Cl2 Ions in Solution per Formula Color Formula Unit (a) CrCl3 ? 6H2O Violet 3 (b) CrCl3 ? 6H2O Light green 2 (c) CrCl3 ? 6H2O Dark green 1 Write modern formulas for these compounds and suggest a method for confirming the number of Cl2 ions present in solution in each case. (Hint: Some of the compounds may exist as hydrates and Cr has a coordination number of 6 in all the compounds.)

The formation constant for the reaction Ag1 1 2NH3 [Ag(NH3)2] 1 is 1.5 3 107 and that for the reaction Ag1 1 2CN2 [Ag(CN)2] 2 is 1.0 3 1021 at 258C (see Table 16.3). Calculate the equilibrium constant and DG8 at 258C for the reaction [Ag(NH3)2] 1 1 2CN2 [Ag(CN)2] 2 1 2NH3

From the standard reduction potentials listed in Table 18.1 for Zn/Zn21 and Cu1/Cu21, calculate DG8 and the equilibrium constant for the reaction Zn(s) 1 2Cu21(aq) Zn21(aq) 1 2Cu1(aq)

Using the standard reduction potentials listed in Table 18.1 and the Handbook of Chemistry and Physics, show that the following reaction is favorable under standard-state conditions: 2Ag(s) 1 Pt21(aq) 2Ag1(aq) 1 Pt(s) What is the equilibrium constant of this reaction at 258C?

The Co21-porphyrin complex is more stable than the Fe21-porphyrin complex. Why, then, is iron the metal ion in hemoglobin (and other heme- containing proteins)?

What are the differences between geometric isomers and optical isomers?

Oxyhemoglobin is bright red, whereas deoxyhemoglobin is purple. Show that the difference in color can be accounted for qualitatively on the basis of high-spin and low-spin complexes. (Hint: O2 is a strong-field ligand; see the Chemistry in Action essay on p. 1016.)

Hydrated Mn21 ions are practically colorless (see Figure 23.20) even though they possess five 3d electrons. Explain. (Hint: Electronic transitions in which there is a change in the number of unpaired electrons do not occur readily.)

Which of the following hydrated cations are colorless: Fe21(aq), Zn21(aq), Cu1(aq), Cu21(aq), V51(aq), Ca21(aq), Co21(aq), Sc31(aq), Pb21(aq)? Explain your choice.

Aqueous solutions of CoCl2 are generally either light pink or blue. Low concentrations and low temperatures favor the pink form while high concentrations and high temperatures favor the blue form. Adding hydrochloric acid to a pink solution of CoCl2 causes the solution to turn blue; the pink color is restored by the addition of HgCl2. Account for these observations.

Suggest a method that would allow you to distinguish between cis-Pt(NH3)2Cl2 and trans-Pt(NH3)2Cl2.

You are given two solutions containing FeCl2 and FeCl3 at the same concentration. One solution is light yellow and the other one is brown. Identify these solutions based only on color.

The label of a certain brand of mayonnaise lists EDTA as a food preservative. How does EDTA prevent the spoilage of mayonnaise?

The compound 1,1,1-trifluoroacetylacetone (tfa) is a bidentate ligand: O B O B CF3CCH2CCH3 It forms a tetrahedral complex with Be21 and a square planar complex with Cu21. Draw structures of these complex ions and identify the type of isomerism exhibited by these ions

How many geometric isomers can the following square planar complex have? a b G D Pt D G d c

[Pt(NH3)2Cl2] is found to exist in two geometric isomers designated I and II, which react with oxalic acid as follows: I 1 H2C2O4 [Pt(NH3)2C2O4] II 1 H2C2O4 [Pt(NH3)2(HC2O4)2] Comment on the structures of I and II.

The Kf for the complex ion formation between Pb21 and EDTA42 Pb21 1 EDTA42 Pb(EDTA)22 is 1.0 3 1018 at 258C. Calculate [Pb21] at equilibrium in a solution containing 1.0 3 1023 M Pb21 and 2.0 3 1023 M EDTA42.

Manganese forms three low-spin complex ions with the cyanide ion with the formulas [Mn(CN)6] 52, [Mn(CN)6] 42, and [Mn(CN)6] 32. For each complex ion, determine the oxidation number of Mn and the number of unpaired d electrons present.

Commercial silver-plating operations frequently use a solution containing the complex Ag(CN)2 2 ion. Because the formation constant (Kf) is quite large, this procedure ensures that the free Ag1 concentration in solution is low for uniform electrodeposition. In one process, a chemist added 9.0 L of 5.0 M NaCN to 90.0 L of 0.20 M AgNO3. Calculate the concentration of free Ag1 ions at equilibrium. See Table 16.4 for Kf value.

Draw qualitative diagrams for the crystal field splittings in (a) a linear complex ion ML2, (b) a trigonalplanar complex ion ML3, and (c) a trigonal-bipyramidal complex ion ML5.

(a) The free Cu(I) ion is unstable in solution and has a tendency to disproportionate: 2Cu1(aq2 Cu21(aq) 1 Cu(s) Use the information in Table 18.1 (p. 821) to calculate the equilibrium constant for the reaction. (b) Based on your result in (a), explain why most Cu(I) compounds are insoluble.

Consider the following two ligand exchange reactions: [Co(H2O)6] 31 1 6NH3 [Co(NH3)6] 31 1 6H2O [Co(H2O)6] 31 1 3en [Co(en)3] 31 1 6H2O (a) Which of the reactions should have a larger DS8? (b) Given that the CoN bond strength is approximately the same in both complexes, which reaction will have a larger equilibrium constant? Explain your choices.

Copper is also known to exist in the 13 oxidation state, which is believed to be involved in some biological electron-transfer reactions. (a) Would you expect this oxidation state of copper to be stable? Explain. (b) Name the compound K3CuF6 and predict the geometry of the complex ion and its magnetic properties. (c) Most of the known Cu(III) compounds have square planar geometry. Are these compounds diamagnetic or paramagnetic?