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Chemistry 1301A/B Study Guide - Final Guide: Crystal Field Theory, Vapor Pressure, Cobalt Blue

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copperyak440
24 Sep 2020
School
Western University
Department
Chemistry
Course
Chemistry 1301A/B
Professor
Christina Booker

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Document Summary

Each cl has four pairs of non-bonding receptor (lewis acid). Both the nh3 and the cl can act as electron pair donors electrons. The electron configuration of pt2+ is 6s0 5d8. The pt2+ is an electron pair (lewis base). Therefore, the formation of this complex may be described as a lewis acid-base reaction. A bidentate ligand contains two donor atoms, or atoms that can bond to the metal centre. A chelate ligand is one in which two or more donor atoms are bound to the same metal centre. Linkage isomers are compounds which differ only by the donor atom of the ligand. If a ligand contains two different donor atoms, there exists the possibility of two different isomers, because each donor atom could bond to the metal centre. Ionization isomers differ by which anions are coordinated and which ones are not. The term coordination number refers to the number of atoms bound directly to the metal centre.

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Related Questions

I want to find the Kn value of Cu(II) and EDTA. I was given the formula kn= [ML4]/[ML3][L]. 12.3 ml of edta was used to tritrate 0.1194 grams of Copper in 50 ml of water. The indicator used was murexide.

At the core of general acid-base theories, there is the concept of ‘transfer’ of one entity to another. In the case of Brønsted-Lowry acid base theory, the transferred entity is the proton, and their transfer processes are widely exploited in chemical methods. In addition to proton transfer, electron pairs can also be donated/shared between donors and acceptors. In this case, an atom/molecule, which can accept a pair of electrons, is referred to as a Lewis acid while the entity donating the pair of electrons is referred to as a Lewis base. The most prevalent Lewis acid-base systems involve metal complexes with vacant nd-orbitals, as well as electron deficient systems including B, Si, Ge, etc. The Lewis acid base theory is also known as the Hard-Soft acid base theory (HSABT) with ‘hardness’ defined as small highly charged species that are weakly polarizable (Lewis acids). In contrast, ‘softness’ is described by species that are larger and highly polarizable species with low charge (Lewis bases).
In the case of metal chemistry, Lewis acid-base theory provides a means to describe the ability of ‘ligands’ to coordinate to metal ions as well as the stability of metal-ligand complexes. Recall that coordination bonds are the donation/acceptance of lone pairs of electrons to empty metal orbitals to another atom; the definition of Lewis acid-base chemistry! The stability of Lewis acid-base complexes can be described through the stability constant which is analogous to the Ka that describes Brønsted-Lowry acidities. Many metal ions can coordinate (bind) many Lewis base ligands in a step-wise fashion according to:
M + L = ML K1 = [ML]/[M][L] Eq. 1
ML + L = ML2 K2 = [ML2]/[ML][L] Eq. 2
ML2 + L = ML3 K3 = [ML3]/[ML2][L] Eq. 3
MLn-1 + L = MLn Kn = [ML4]/[ML3][L] Eq. 4
and for which the free energy for this dissociation reaction is given by:
ΔG0 = -RTLnKn Eq. 5.
where R is the gas constant and T is the temperature in Kelvin.
Figure 1: Left- EDTA. Right- Typical EDTA-transition metal complex.
The ethylene diamine tetraacetic acid ligand (EDTA, a Lewis base) provides a mechanism to probe the Lewis acid strength of various metal complexes (Figure 1). This multi-dentate ligand (multiple Lewis base sites on a single ligand) forms complexes with metals of the form:
Mn+ + Y4- = MYn-4 Eq. 6
K = [MYn-4]/[Mn+][Yn-4] Eq. 7
where Y4- is the EDTA ligand.
In this experiment, the Lewis acid strength for two different metals will be examined by measuring the stability constants for the metal-EDTA complex. Of specific interest is the how the Lewis acid strength of the metal ion correlates with:
1) atomic/ionic radii, 2) oxidation state, 3) electron configuration, and 4) polarizability.
You will determine the stability constants of both a Cu2+- and Zn2+-EDTA complexes as well as the corresponding free energy. Using these data, you will compare the relative Lewis acidities of both metals and describe differences in terms of the metal ion properties described above.
.
Chemicals
CuSO4
ZnSO4
EDTA
Murexide
Instruments
Buret
Experimental
You and your group will determine the concentration and ultimately the free energy of Cu(II) and Zn(II) using the hexadentate chelating ligand, EDTA.
You will be given a ~100 mM standardized solution of EDTA (check the label for exact concentration prior to beginning). You will need to weigh ~0.1 g per metal salt sample. Dissolve the metal salt into 50 mL of DI water. Add 2-3 drops of murexide to your metal. After properly preparing your buret with EDTA, titrate your metal with EDTA. Repeat for a total of 3 titrations per metal.
1. Approximately how much EDTA will you need for each titration assuming the metal-salts’ masses are accurate?
2. What type of indicator is murexide and what color will its endpoint be?
Post-Lab Questions
1.
a) Using the equations given in the introduction and your titration results, what are the Kn of the EDTA-Copper complex? Show calculations.
b) Using the equations given in the introduction and your titration results, what are the Kn of the EDTA-Zinc complex? Show calculations.
2. What are the corresponding ΔG values for the EDTA-metal complexes? Show your calculations
3. Would copper be considered a hard or soft lewis acid? What about zinc? Describe what makes these metals hard or soft.
4. What trends would you predict for EDTA-metal complex Kn and ΔG values when:
a) going down a row of transition metals of the same oxidation state?
b) of the same transition metal with increasing oxidation state? (For example, Iron can exist as Fe(II), Fe(III), Fe(IV), and higher oxidation states)
5. Discussion (formal report style): Compare and contrast the concepts of Lewis and Brønsted-Lowry acids and bases. Support these concepts with your data over the last two weeks and with research. Cite your sources.

Which of the following does not have a more stable resonance structure?

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Question 21 pts

In the following molecule, which carbons are electron deficient, meaning they hold a partial positive charge (δ+) in the hybrid structure. All carbon atoms are identified by a number.

2, 4, and 6
4, 6 and 7
2, 4, 6 and 7
3, 5, and 6

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Question 31 pts

Rank the following resonance structures from most to least stable.

III (most stable) > I > II (least stable)
III (most stable) > II > I (least stable)
I (most stable) > II > III (least stable)
II (most stable) > III > I (least stable)

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Question 41 pts

Which of the following accurately depicts a Lewis acid-base reaction where a carbon is acting as the Lewis acid and an oxygen is acting as the Lewis base.

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Question 51 pts

Which of the following statements about Lewis acids and bases is true?

A Lewis base always accepts an electron pair from a Lewis acid.

The interaction between a Lewis acid and a Lewis base creates a covalent bond.

Lewis acids are also commonly called nucleophiles.

A Lewis base always accepts a proton (H+) from a Lewis acid.

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Question 61 pts

A molecular orbital energy diagram was created that contains two bonding orbitals and two antibonding orbitals. How many atomic orbitals were mixed to create all these orbitals?

6
8
4
2

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Question 71 pts

Which of the following statements about the molecular orbital diagram for H2– is false?

Two atomic orbitals combine to produce two molecular orbitals.
There is one filled bonding orbital.
There is one empty antibonding orbital.
There is a non-zero bond order.

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Question 81 pts

If a p atomic orbital and an s atomic orbital were to interact and combine to create new molecular orbitals, how many antibonding molecular orbitals would be created?

0
1
4
2

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Question 91 pts

Which of the following contains an aldehyde, an ether and an alcohol? Choose all that apply.

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Question 101 pts

Which of the following contains a carboxylic acid and an ether? Choose all that apply.

4. (20 pts, 2 pts each) Multiple choice questions from chapter 7.Place the letter representing the
correct response in the blank provided.
_____ Which of the following do not exist under normal conditionsas a diatomic gas?
(A) hydrogen, (B) oxygen, (C) fluorine, (D) chlorine, (E)bromine
_____ In nature, the noble gases exist as
(A) monatomic gaseous atoms, (B) the gaseous fluorides, (C) solidsin minerals,
(D) alkali metal salts, (E) the sulfides
_____ Of the elements below, _____ has the highest electronaffinity.
(A) oxygen, (B) sodium, (C) fluorine, (D) hydrogen, (E)chlorine
_____ Of the following elements, which has the largest firstionization energy?
(A) Se, (B) As, (C) S, (D) Sb, (E) Ge
_____ Of the hydrogen halides, only _____ is a weak acid.
(A) HCl (aq), (B) HBr (aq), (C) HF (aq), (D) HI (aq), (E) all ofthem
_____ The carbonate of which alkali metal is used in treatment ofmanic-depressive illness?
(A) Li, (B) Na, (C) K, (D) Rb, (E) Cs
_____ The reaction of a metal with a nonmetal produces a(n)
(A) base, (B) salt, (C) acid, (D) oxide, (E) hydroxide
_____ Which element is solid at room temperature?
(A) Cl2, (B) F2, (C) Br2, (D) I2, (E) H2
_____ Which of the following correctly lists the five atoms inorder of increasing size (smallest to
largest)?_(A) F < K < Ge < Br < Rb, (B) F < Ge <Br < K < Rb,
(C) F < K < Br < Ge < Rb, (D) F < Br < Ge < K< Rb, (E) F < Br < Ge < Rb < K
_____ Which one of the following is a metalloid?
(A) Ge, (B) S, (C) Br, (D) Pb, (E) C
5. (20 pts, 2 pts each) Multiple choice questions from chapter 8.Place the letter representing the
correct response in the blank provided.
_____ Which of the following ions does not have a noble-gasconfiguration?
(A) V5+ (B) Si4+ (C) Nb3+ (D) S2– (E) Os8+
_____ Which of the following is correctly arranged with respect tothe size of the atom/ion?
(A) S < S1– < S2– (B) Mg2+ < Na+ < Ne (C) Ni < Cu+< Zn2+
_____ What type of covalent bond between like atoms is thelongest?
(A) triple (B) double (C) single (D) They are all the samelength.
_____ Arrange the following in order of increasing bond polarity:C-O, P-O, Cu-O, Mn-O
(A) C-O < P-O < Cu-O < Mn-O (B) C-O < P-O < Mn-O< Cu-O
(C) Mn-O < Cu-O < P-O < C-O (D) P-O < C-O < Cu-O< Mn-O
_____ Write a single Lewis structure that obeys the octet rule, andcalculate the formal charges on
all the atoms in PO4
3–.
(A) P 2+, O 1– (B) P 1+, O 1– (C) P 4+, O 2– (D) P 2+, O 2– (E) P1+, O 2–
_____ The Lewis structure of InBr3 contains how many valenceelectrons?
(A) 24 (B) 7 (C) 6 (D) 3 (E) 34
_____ Using Lewis structures that satisfy the octet rule, determinethe number of bonds formed by
the central element in each of the following: SiO4
4–, PO4
3–, SO4
2–, ClO4
1–.
(A) 4, 5, 6, 7 (B) 2, 3.5, 5, 6.5 (C) 4, 5, 5, 6 (D) 4, 4, 4, 4 (E)5, 6, 7, 8
_____ The Lewis electron-dot structure of IF5 gives the centralI
(A) an octet (B) 5 nonbonding pairs and 1 bonding pair (C) 5bonding pairs only
(D) 1 nonbonding pairs and 5 bonding pairs (E) 1 nonbonding pairand 4 bonding pairs
_____ In the thiocyanate anion, (SCN)–, which of the following isnot an accepted multiplicity for
the sulfur-carbon bond and the carbon-nitrogen bond,respectively?
(A) single, single (B) double, double (C) single, triple (D)triple, single
_____ Which of these ions (oxidation states) does not have anoble-gas configuration?
(A) Cr3+ (B) Cr with an oxidation state of 6+ (as in CrO4
2–)
(C) S with an oxidation state of 6+ (as in SO4
2–) (D) S2– (E) Hf 4+