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Chemistry: Structure and Properties | 2nd Edition | ISBN: 9780134293936 | Authors: Nivaldo J. Tro ISBN: 9780134293936 2043

Solution for problem 86 Chapter 22

Chemistry: Structure and Properties | 2nd Edition

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Chemistry: Structure and Properties | 2nd Edition | ISBN: 9780134293936 | Authors: Nivaldo J. Tro

Chemistry: Structure and Properties | 2nd Edition

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Problem 86

Many aqueous solutions of complex ions display brilliant colors that depend on the identities of the metal ion and ligand(s). Some ligands bind selectively to certain metal ions and produce a complex ion with characteristic colors. These distinctive complex ions serve as qualitative indicators of the presence of particular metal ions. For example, \(\mathrm{Fe}^{3+}\) is identified by the rapid formation of the intensely colored pentaaquathiocyanatoiron(III) complex ion, \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\), when thiocyanate, \(\mathrm{SCN}^{-}\), is added to a solution containing hexaaquairon(III), \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\), according to the balanced chemical equation shown here:

\(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}(a q)+\mathrm{SCN}^{-}(a q) \rightleftharpoons\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)

pale violet                    colorless               intensely colored

Examine the absorption spectrum of an aqueous solution of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) shown here and answer the questions.

                                     

a. Based on the spectrum, what is the color of an \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) solution?

b. Calculate the crystal field splitting energy,\(\Delta\), of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) in kJ/mol.

c. The hexaaquairon(III) complex ion, \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\), produces a pale violet aqueous solution. Is the crystal field splitting energy, \(\Delta\), of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) smaller or larger than the \(\Delta\)  of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)?

d. On the basis of your answers to parts b and c, compare the crystal field strengths of water and thiocyanate ligands.

e. The complex ion hexacyanoferrate(III), \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\), is red in aqueous solution. What can you conclude about the relative crystal field splitting energies of \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) and \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)?

Text Transcription:

Fe^3+

[Fe(H_2O)_5SCN]^2+

SCN^-

[Fe(H_2O)_6]^3+

[Fe (H_2O)_6]^3+(aq) SCN^-(aq)rightleftharpoons[Fe(H_2O)_6]^3+

[Fe(CN)_6]^3-

delta

Step-by-Step Solution:
Step 1 of 3

Chapter 2: 9/6/2016 Cation and anions Monatomic and polyatomic ions Ionic compounds - Recognizing them and - building a balanced molecular formulas give the exact number of atoms of each element in a compound empirical formulas give the lowest whole number ration of atoms of each element in a compound structural formulas show the order in which atoms are bonded (the connectivity) Oxidation Numbers: the atomic charge of a cation or anion in an ionic compound is also called its oxidation number for a molecular compound the atoms don’t have charges like in ionic compounds 1. pure elements are assigned zero for their oxidation number 2. ions have the oxidation number of their common charge anion- ide cation- ate 3. common oxidation numbers of H, F, and O o Hydrogen (H): i. +1 when bonded to nonmetal ii. -1 when bonded to a metal o Fluorine (F) is always -1 o Oxygen (O): iii. -2 in almost all compounds iv. -1 in peroxides v. Exception: +2 in OF2 4. Compounds and polyatomic ions o in a neutral compound, the sum of the oxidation numbers of all elements in the formula must equal zero o in polyatomic ion the sum of the oxidation numbers of all elements in the formula must equal the net charge on the ion o in general the more electronegative Acids and Bases - hydrogen cation (H+) also called the proton - hydroxide anion (OH-) Acid: substance that produces H+ in

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Chapter 22, Problem 86 is Solved
Step 3 of 3

Textbook: Chemistry: Structure and Properties
Edition: 2
Author: Nivaldo J. Tro
ISBN: 9780134293936

Chemistry: Structure and Properties was written by Aimee Notetaker and is associated to the ISBN: 9780134293936. This textbook survival guide was created for the textbook: Chemistry: Structure and Properties, edition: 2. This full solution covers the following key subjects: . This expansive textbook survival guide covers 23 chapters, and 130 solutions. The full step-by-step solution to problem: 86 from chapter: 22 was answered by Aimee Notetaker, our top Chemistry solution expert on 04/25/22, 03:51PM. The answer to “?Many aqueous solutions of complex ions display brilliant colors that depend on the identities of the metal ion and ligand(s). Some ligands bind selectively to certain metal ions and produce a complex ion with characteristic colors. These distinctive complex ions serve as qualitative indicators of the presence of particular metal ions. For example, \(\mathrm{Fe}^{3+}\) is identified by the rapid formation of the intensely colored pentaaquathiocyanatoiron(III) complex ion, \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\), when thiocyanate, \(\mathrm{SCN}^{-}\), is added to a solution containing hexaaquairon(III), \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\), according to the balanced chemical equation shown here:\(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}(a q)+\mathrm{SCN}^{-}(a q) \rightleftharpoons\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)pale violet colorless intensely coloredExamine the absorption spectrum of an aqueous solution of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) shown here and answer the questions. a. Based on the spectrum, what is the color of an \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) solution?b. Calculate the crystal field splitting energy,\(\Delta\), of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\) in kJ/mol.c. The hexaaquairon(III) complex ion, \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\), produces a pale violet aqueous solution. Is the crystal field splitting energy, \(\Delta\), of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\) smaller or larger than the \(\Delta\) of \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)?d. On the basis of your answers to parts b and c, compare the crystal field strengths of water and thiocyanate ligands.e. The complex ion hexacyanoferrate(III), \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\), is red in aqueous solution. What can you conclude about the relative crystal field splitting energies of \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\) and \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{5} \mathrm{SCN}\right]^{2+}\)?Text Transcription:Fe^3+[Fe(H_2O)_5SCN]^2+SCN^-[Fe(H_2O)_6]^3+[Fe (H_2O)_6]^3+(aq) SCN^-(aq)rightleftharpoons[Fe(H_2O)_6]^3+[Fe(CN)_6]^3-delta” is broken down into a number of easy to follow steps, and 227 words. Since the solution to 86 from 22 chapter was answered, more than 209 students have viewed the full step-by-step answer.

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