What are the oxidation states of Fe and Ti in the ore

Problem 80AP Copper is known to exist in the +3 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 and magnetic properties of the complex ion. (c) Most of the known Cu(III) compounds have square planar geometry. Are these compounds diamagnetic or paramagnetic?

Problem 1QP What distinguishes a transition metal from a main group metal?

Problem 3QP Explain why atomic radii decrease very gradually from scandium to copper.

Problem 2QP Why is zinc not considered a transition metal?

Problem 4QP Without referring to the text, write the ground-state electron configurations of the first-row transition metals. Explain any irregularities.

Problem 5QP Write the electron configurations of the following ions: V5+, Cr3+, Mn2+, Fe3+, Cu2+, Sc3+, Ti4+.

Problem 6QP Why do transition metals have more oxidation states than other elements?

Problem 7QP Give the highest oxidation states for scandium to copper.

Problem 9QP Describe the interaction between a donor atom and a metal atom in terms of a Lewis acid–base reaction.

Problem 8QP Define the following terms: coordination compound, ligand, donor atom, coordination number, chelating agent.

Complete the following statements for the complex ion \(\left[\mathrm{Co}(\mathrm{en})_2\left(\mathrm{H}_2 \mathrm{O}\right) \mathrm{CN}\right]^{2+}\). (a) en is the abbreviation for ____________ (b) The oxidation number of \(\mathrm{Co}\) is ____________ (c) The coordination number of \(\mathrm{Co}\) is ____________ (d) ____________ is a bidentate ligand.

Problem 11QP Complete the following statements for the complex ion [Cr(C2O4)2(H2O)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) \(\mathrm{K}_3\left[\mathrm{Fe}(\mathrm{CN})_6\right]\), (b) \(\mathrm{K}_3\left[\mathrm{Cr}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]\), (c) \(\left[\mathrm{Ni}(\mathrm{CN})_4\right]^{2-}\).

Problem 13QP Give the oxidation numbers of the metals in the following species:

Problem 14QP What are the systematic names for the following ions and compounds?

What are the systematic names for the following ions and compounds? (a) \(\left[\text { cis-Co(en) } \mathrm{Cl}_2\right]^{+}\) (b) \(\left[\mathrm{Pt}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right] \mathrm{Cl}_3\) (c) \(\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right] \mathrm{Cl}_2\)

Problem 16QP Write the formulas for each of the following ions and compounds: (a) tetrahydroxozincate(II), (b) pentaaqua- chlorochromium(III) chloride, (c) tetrabromocuprate(II), (d) ethylenediaminetetraacetatoferrate(II).

Problem 19QP Specify which of the following structures can exhibit geometric isomerism: (a) linear, (b) square planar, (c) tetrahedral, (d) octahedral.

Problem 20QP What determines whether a molecule is chiral? How does a polarimeter measure the chirality of a molecule?

Problem 21QP Explain the following terms: enantiomers, racemic mixtures.

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

Problem 18QP Define the following terms: stereoisomer, geometric isomers, optical isomers, plane-polarized light.

Problem 23QP How many geometric isomers are in the following species: (a) [Co(NH3)2Cl4]?, (b)[Co(NH3)3Cl3]?

Problem 24QP Draw structures of all the geometric and optical isomers of each of the following cobalt complexes:

Problem 25QP Draw structures of all the geometric and optical isomers of each of the following cobalt complexes: (a)

Problem 26QP Briefly describe crystal field theory.

Problem 27QP Define the following terms: crystal field splitting, high-spin complex, low-spin complex, spectrochemical series.

Problem 28QP What is the origin of color in a coordination compound?

Problem 30QP 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.

Compounds containing the \(\mathrm{Sc}^{3+}\) ion are colorless, whereas those containing the \(\mathrm{Ti}^{3+}\) ion are colored. Explain.

Problem 31QP Transition metal complexes containing CN? ligands are often yellow in color, whereas those containing H2O ligands are often green or blue. Explain.

Problem 33QP The absorption maximum for the complex ion [Co(NH3)6]3+ occurs at 470 nm. (a) Predict the color of the complex, and (b) calculate the crystal field splitting in kJ/mol.

Problem 32QP Predict the number of unpaired electrons in the following complex ions:

Problem 34QP From each of the following pairs, choose the complex that absorbs light at a longer wavelength: (a) [Co(NH3)6]2+,[Co(H2O)6]2+;

Problem 35QP A solution made by dissolving 0.875 g of Co(NH3)4Cl3 in 25.0 g of water freezes at ?0.56°C. 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.

In biological systems, the \(\mathrm{Cu}^{2+}\) ions coordinated with \(\mathrm{S}\) atoms tend to form tetrahedral complexes, whereas those coordinated with \(\mathrm{N}\) atoms tend to form octahedral complexes. Explain.

Problem 37QP Plastocyanin, a copper-containing protein found in photosynthetic systems, is involved in electron transport, with the copper ion switching between the +1 and +2 oxidation states. The copper ion is coordinated with two histidine residues, a cysteine residue, and a methionine residue in a tetrahedral configuration. How does the crystal field splitting (?) change between these two oxidation states?

Problem 38QP Define the terms labile complex and inert complex.

Problem 39QP Explain why a thermodynamically stable species may be chemically reactive and a thermodynamically unstable species may be unreactive.

Problem 40QP Oxalic acid (H2C2O4) is sometimes used to clean rust stains from sinks and bathtubs. Explain the chemistry underlying this cleaning action.

Problem 41QP The [Fe(CN)6]3? complex is more labile than the [Fe(CN)6]4? complex. Suggest an experiment that would prove that [Fe(CN)6]3? 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.

Problem 43QP 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.

Problem 44QP A concentrated aqueous copper(II) chloride solution is bright green in color. When diluted with water, the solution becomes light blue. Explain.

Problem 45QP In a dilute nitric acid solution. Fe3+ reacts with thiocyanate ion (SCN?) to form a dark-red complex: The equilibrium concentration of [Fe(H2O)5NCS]2+ 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 × 10?3 M KSCN and 8.0 mL of dilute HNO3. The color of the solution quantitatively indicated that the [Fe(H2O)5NCS]2+ concentration was 7.3 × 10?5M Calculate the formation constant for [Fe(H2O)5NCS]2+

Problem 46QP Describe and give examples of the applications of coordination compounds.

Problem 47AP Suffocation victims usually look purple, but a person poisoned by carbon monoxide often has rosy cheeks. Explain.

As we read across the first row transition metals from left to right, the \(+2\) oxidation state becomes more stable in comparison with the \(+3\) state. Why is this so?

Problem 49AP Which is a stronger oxidizing agent in aqueous solution. Mn3+ or Cr3+? Explain your choice.

Problem 50AP 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-to-ligand sigma bond is formed by donating a lone pair from the donor atom to an empty sp3d2 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.

Problem 51AP 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 22.1: the fourth ionization energy of Ti is 4180 kJ/mol.)

Problem 52AP A student has prepared a cobalt complex that has one of the following three structures: [Co(NH3)6]Cl3, [Co(NH3)5.Cl]Cl2, or(Co(NH3)4Cl2]Cl. Explain how the student would distinguish between these possibilities by an electrical conductance experiment. At the student’s disposal are three strong electrolytes —NaCl, MgCl2, and FeCl3— which may be used for comparison purposes.

Problem 53AP 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?

Problem 54AP 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.

Problem 55AP A student in 1895 prepared three coordination compounds containing chromium, with the following properties: Formula Color Cl? Ions in Solution per Formula Unit (a) CrCl3• 6H2O Violet 3 (b) CrCl3 •6H2O Light green 2 (C) CrCl3 •6H2O Dark green 1 Write modem formulas for these compounds, and suggest a method for confirming the number of Cl? ions present in solution in each case. (Hint: Some of the compounds may exist as hydrates.)

Problem 56AP The formation constant for the reaction Ag + 2NH3 ? [Ag(NH3)2]+ is 1.5 × 107, and that for the reaction Ag + 2CN ?[Ag(CN)2] is 1.0 ×1021 at 25°C(see Table 17.5). Calculate the equilibrium constant and ?Go at 25°C for the reaction

Problem 57AP From the standard reduction potentials listed in Table 19.1 for Zn/Zn2 and Cu/Cu2+, calculate ?Go and the equilibrium constant for the reaction

Problem 58AP Using the standard reduction potentials listed in Table 19.1 and the Handbook of Chemistry and Physics, show that the following reaction is favorable under standard-state conditions: What is the equilibrium constant of this reaction at 25°C?

Problem 59AP The Co2+ -porphyrin complex is more stable than the Fe2+ - porphyrin complex. Why, then, is iron the metal ion in hemoglobin (and other heme-containing proteins)?

Problem 61AP 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 Bringing Chemistry to Life box on page 938.)

Problem 60AP What are the differences between geometric isomers and optical isomers?

Hydrated \(\mathrm{Mn}^{2+}\) ions are practically colorless (see Figure 22.16) 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: \(\mathrm{Fe}^{2+}(a q), \mathrm{Zn}^{2+}(a q), \mathrm{Cu}^{+}(a q), \mathrm{Cu}^{2+}(a q), \mathrm{V}^{5+}(a q), \mathrm{Ca}^{2+}(a q)\), \(\mathrm{Co}^{2+}(a q), \mathrm{Sc}^{3+}(a q), \mathrm{Pb}^{2+}(a q) \text { ? }\) Explain your choice.

Problem 64AP Aqueous solutions of CoCl2: are generally either light pink or blue. Low concentrations and low temperatures favor the pink form. whereas 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.

Problem 65AP Suggest a method that would allow you to distinguish between cis-Pt(NH3)2;Cl2 and trans-Pt(NH3)2Cl2.

You are given two solutions containing \(\mathrm{FeCl}_2\) and \(\mathrm{FeCl}_3\) at the same concentration. One solution is light yellow, and the other one is brown. Identify these solutions based only on color.

Problem 67AP The label of a certain brand of mayonnaise lists EDTA as a food preservative. How does EDTA prevent the spoilage of mayonnaise?

Problem 68AP The compound l,l,l-trifluoroacetylacelone(tfa) is a bidentate ligand: It forms a tetrahedral complex with Be2+ and a square-planar complex with Cu2+. Draw structures of these complex ions, and identify the type of isomerism exhibited by these ions.

Problem 69AP How many geometric isomers can the following square-planar complex have?

Problem 70AP [Pt(NH3)2Cl2] is found to exist in two geometric isomers designated 1 and II. which react with oxalic acid as follows: Comment on the structures of I and II.

Problem 72AP Draw qualitative diagrams for the crystal field splittings in (a) a linear complex ion ML2,(b) a trigonal-planar complex ion ML3, and (c) a trigonal-bipyramidal complex ion ML5.

Problem 73AP (a) The free Cu(I) ion is unstable in solution and has a tendency to disproportionate: Use the information in Table 19.1 (page 827) to calculate the equilibrium constant for the reaction, (b) Based on your results in part (a), explain why most Cu(I) compounds are insoluble.

Consider the following two ligand exchange reactions: \(\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}+6 \mathrm{NH}_3 \rightleftarrows\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_6\right]^{3+}+6 \mathrm{H}_2 \mathrm{O}\) \(\left[\mathrm{Co}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}+3 \mathrm{en} \rightleftarrows\left[\mathrm{Co}(\mathrm{en})_3\right]^{3+}+6 \mathrm{H}_2 \mathrm{O}\) (a) Which of the reactions should have a larger \(\Delta S^{\circ}\)? (b) Given that the \(\mathrm{Co}-\mathrm{N}\) bond strength is approximately the same in both complexes, which reaction will have a larger equilibrium constant? Explain your choices.

Problem 75AP The Cr3+ ion forms octahedral complexes with two neutral ligands X and Y. The color of is blue while that of is yellow. Which is a stronger field ligand. X or Y?

Explain the difference between these two compounds: \(\mathrm{CrCl}_3 \cdot 6 \mathrm{H}_2 \mathrm{O}\) and \(\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right] \mathrm{Cl}_3\).

Problem 77AP The Kf for the formation of the complex ion between Pb2+ and EDTA4?, is 1.0 × 1018 at 25°C. Calculate [Pb2+] at equilibrium in a solution containing 1.0× 10?3 MPb2+ and 2.0 ×10?3 M EDTA4? .

Problem 78AP Locate the transition metal atoms and ions in the periodic table shown here. Atoms: (a) [Kr]5s24d5. (b) [Xe]6s24f145d4. Ions: (c) [Ar]3d3 (ion with charge 4+). (d) [Xe]4fl45d8 (ion with charge 3+).

Problem 79AP Manganese forms three low-spin complex ions with the cyanide ion with the formulas [Mn(CN)6]5? [Mn(CN)6]4?, and [Mn(CN)6)3?. For each complex ion, determine the oxidation number of Mn and the number of unpaired d electrons.

One of the drugs commonly used for chelation therapy is dimercaptosuccinic acid (DMSA), marketed under the name Chemet. How many donor atoms does DMSA have?

Commercial silver-plating operations frequently use a solution containing the complex \(\mathrm{Ag}(\mathrm{CN})_{2}^{-}\) ion. Because the formation constant \(\left(K_{\mathrm{f}}\right)\) is quite large, this procedure ensures that the free \(\mathrm{Ag}^{+}\) 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 \(\mathrm{AgNO}_{3}\). Calculate the concentration of free \(\mathrm{Ag}^{+}\) ions at equilibrium. See Table 17.5 for \(K_{\mathrm{f}}\) value.