CH3410, Final Exam, C98

1. Which choice is an acceptable Lewis structure for XeO₂F₂ ? Lone pairs on terminal atoms not shown. Answer, 4).

2. The diagram that best represents the molecular stereochemistry of XeO₂F₂ is 4)

3. Which compound is expected to be most ionic?

1) BeCl₂

2) TlCl

3) GaCl₃

4) PCl₅

5) SiCl₄

4. Which cation produces the most acidic solution when its chloride is contacted with water?

1) V⁵⁺

2) Fe³⁺

3) Sr²⁺

4) Sb³⁺

5. Which species is most likely to occur in the upper right hand corner of the Pourbaix diagram for iodine?

1) HI

2) I₂

3) HIO₄

4) I^-

Questions 6-10 concern the following redox half reactions and their corresponding standard reduction potentials

1) Cr₂O₇^2-(aq) + 14 H⁺(aq) + 6e ®2Cr³⁺(aq) + 7H₂O e⁰ = 1.33 V

2) Br₂(l) + 2e ® 2Br^-(aq) e⁰ = 1.07 V

3) Mg²⁺(aq) + 2e ®Mg(s) e ⁰ = -2.38 V

4) Ni²⁺(aq) + 2e ® Ni(s) e⁰ = -0.23 V

5) Hg₂²⁺(aq) + 2e ® 2Hg(l) e ⁰ = 0.80 V

6. The half reaction that is most spontaneous as written under standard conditions is 1.

7. The strongest oxidant (oxidizing agent) is in reaction 1.

8. The strongest reductant (reducing agent) is in reaction 3.

9. The half reaction whose reduction potential depends on pH is 1.

10. The reaction having the most positive standard free energy change is 3.

11. The first few pK_a values for H₅IO₆ are 1.8, 7.3, and 11.8. Which species will predominate in an aqueous solution having pH = 10.2?

1) H₅IO₆

2) H₄IO₆^-

3) H₃IO₆^2-

4) H₂IO₆^3-

5) HIO₆^4-

12. Which substance is expected to have the lowest boiling point?

1) NF₃

2) AlF₃

3) ClF₃

4) BrF₃

5) FeF₃

13. Which fundamental property of the atom is primarily responsible for the fact that the first ionization energy tends to decrease top to bottom in a group of the Periodic Table?

1) Electronegativity

2) Effective nuclear charge

3) Enthalpy of atomization

4) Atomic number

14. Which substance is unlikely to function as a Lewis base?

1) SO₂

2) (CH₃)₃N

3) (C₂H₅)₂O

4) (CH₃)₄Si

5) C₂H₄

15. The stereochemistry of XeF₃⁺ is best described as

1) tetrahedral

2) square planar

3) trigonal planar

4)see-saw

16. Which structure for BN is reasonable in terms of expected bonding patterns for B and N? Answer, 2.

17. Which hydrogen compound produces a basic solution when dissolved in water?

1) IH

2) SH₂

3) SbH₃

4) MgH₂

5) H₂

18. Reaction of the Lewis acid, SbF₅, with the Lewis base, F^-, gives the adduct, SbF₆^-. Which statement is true?

1) Hybridization at Sb changes from sp³ to sp³d.

2) Hybridization at Sb does not change.

3) Hybridization at Sb changes from sp³d² to sp³d³.

5) Hybridization at F^- changes from sp³ to sp³d.

19. How many reasonable resonance forms can be drawn for H₂SeO₄? All answers given credit; my screwup

1) one

2) five

3) eleven

4) fifteen

5) twenty

20. Which Lewis acid is expected to have the greatest affinity for the Lewis base, OH^-?

1) H⁺

2) SO₃

3) BF₃

4) Sn⁴⁺

5) Pb²⁺

21. Which substance is expected to be insoluble in water?

1) AlBr₃

2) Al(ClO₄)₃

3) Al₂(SO₄)₃

4) AlPO₄

5) Al(NO₃)₃

22. Silicate anions

1) usually react vigorously with water

2) are based on trigonal planar SiO₃ units sharing triangle edges

3) contain sp³d hybridized Si

5) are rare in nature

23. Hybrid orbitals used by Xe in XeO₂F₂ are best described as

1) sp²

2) sp³

3) sp⁴

4) sp³d

5) sp³d²

24. The reaction (CH₃)₃C⁺ + I^- ® (CH₃)₃CI is best described as

2) Lewis adduct dissociation

3) Diels-Alder addition

4) redox

5) double displacement

25. Which species would be predicted by VSEPR to have square planar stereochemistry?

1) CF₄

2) SeF₄

3) ClF₄^-

4) ClF₄⁺

5) PF₄⁺