Organic Practice

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Transcript of Organic Practice

Chapter 1

MULTIPLE CHOICE QUESTIONS Topic: Atomic Orbitals 1. A) B) C) D) E) In quantum mechanics a node (nodal surface or plane) is: a place where is negative. a place where is positive. a place where = 0. a place where 2 is large. a place where 2 is negative. Ans: C

Topic: Atomic Orbitals, Molecular Orbitals 2. When the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule, how many molecular orbitals are formed? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: B Topic: Atomic Orbitals 3. Which principle(s) or rule must be used to determine the correct electronic configuration for carbon in its ground state? A) Aufbau Principle B) Hund's Rule C) Pauli Exclusion Principle D) (A) and (B) only E) All three Ans: E

1

Chapter 1

Topic: Atomic Orbitals, Bonding 4. What point on the potential energy diagram below represents the most stable state for the hydrogen molecule?

A) B) C) D) E)

I II III IV V Ans: C

Topic: Atomic Orbitals, Molecular Orbitals 5. A) B) C) D) E) According to molecular orbital theory, which molecule could not exist? H2 He2 Li2 F2 N2 Ans: B

Topic: Atomic Orbitals, Molecular Orbitals 6. When the ls orbitals of two hydrogen atoms combine to form a hydrogen molecule, which molecular orbitals are formed? A) One bonding molecular orbital only B) Two bonding molecular orbitals C) One bonding molecular orbital and one antibonding molecular orbital D) Two antibonding molecular orbitals E) Three bonding molecular orbitals Ans: C

2

Chapter 1

Topic: Atomic Orbitals, Hybridization 7. The following electron configuration represents _______.

A) B) C) D) E)

1s 2sp3 2sp3 2sp3 2sp3 the ground state of boron. the sp3 hybridized state of carbon. the sp3 hybridized state of nitrogen. the ground state of carbon. an excited state of carbon. Ans: C

Topic: Atomic Orbitals, Molecular Orbitals 8. According to molecular orbital theory, in the case of a carbon-carbon double bond, the carbon-carbon bonding electrons of higher energy occupy this molecular orbital. A) bonding MO B) bonding MO C) * antibonding MO D) * antibonding MO E) * bonding MO Ans: B Topic: Atomic Orbitals, Hybridization 9. A) B) C) D) E) Identify the atomic orbitals in the C-C sigma bond in ethyne. (2sp2, 2sp2) (2sp3, 2sp3) (2sp, 2sp) (2p, 2p) (2sp, 1s) Ans: C

3

Chapter 1

Topic: Lewis Structures, Formal Charges 10. Listed below are electron dot formulas for several simple molecules and ions. All valence electrons are shown; however, electrical charges have been omitted deliberately. H .. H:B:H .. H II H .. H:N:H .. III H .. H:N:H .. H IV H .. H:O:H .. V

H : Be : H

I

A) B) C) D) E)

Which of the structures actually bear(s) a positive charge? I II III III & V IV & V Ans: E

Topic: Lewis Structures, Formal Charges 11. What is the formal charge on oxygen in the following structure? ..H3C O CH3 CH3

A) B) C) D) E)

+2 +1 0 -1 -2 Ans: B

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Chapter 1

Topic: Lewis Structures, Formal Charges 12. In which structure(s) below does the oxygen have a formal charge of +1?

..H O H H H

O:

.. ..

..H C H O H H3C

..O CH3 CH3

Is

II

III

IV

A) B) C) D) E)

I only II only I and III I and IV I, III, and IV Ans: E

Topic: Lewis Structures, Formal Charges 13. Which structure(s) contain(s) an oxygen that bears a formal charge of +1? .. .. :O :O .. .. .. .. : O C O: H C H3C O H H3C O CH3 C : O. : : O. : : O. : . . . CH3 H I II III IV V A) B) C) D) E) I and II III and IV V II I and V Ans: B

5

Chapter 1

Topic: Lewis Structures, Formal Charges 14. Which of the following molecules or ions has a nitrogen with a formal charge of -1? (Charges on ions have been omitted.) .. A) : N HH

B) H C) H D) H3C

..N H

.H .N H CH3

..N H CH3

E) H3C C Ans: A

N:

Topic: Lewis Structures, Formal Charges 15. In which structure(s) below does nitrogen have a formal charge of +1?H3C N H CH2 H3C

.. N .. II

H H H

..N

.. OH ..

..H3C NH2

..H3C N CH3 CH3

I

III

IV

V

A) B) C) D) E)

I II and IV III and V I and V V Ans: A

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Chapter 1

Topic: Lewis Structures, Formal Charges 16. Which of the following is an ion with a single negative charge? .. A) H3C O : . . .. . .. . B) : O N O : .. .. C) : O: .. :O N : O. : . D) All of these E) None of these Ans: D Topic: Lewis Structures, Formal Charges 17. Which of these is a correct electron-dot representation of the nitrite ion, NO2-? .. .. .. .. .. .. .. : O : : N : : .. :O:N::O O :O::N:O: .. .. .. .. .. I II III

.. .. .. :O:N:O: .. ..IV A) B) C) D) E) I II III IV V Ans: A

.. .. .. :O::N:O .. ..V

7

Chapter 1

Topic: Lewis Structures, Formal Charges 18. Which is NOT a correct Lewis structure? .. A) H N F : .. B)HH H

C H .. O ..

.. F: ..

C) H D)H

: O. H . E) None of these Ans: A

.. O ..

.. O H . .. . :O HB

Topic: Lewis Structures, Formal Charges 19. Listed below are electron dot formulas for several simple molecules and ions. All valence electrons are shown; however, electrical charges have been omitted deliberately. H .. H:B:H .. H II H .. H:N:H .. III H .. H:N:H .. H IV H .. H:O:H .. V

H : Be : H

I

A) B) C) D) E)

Which of the structures is negatively charged? I II III IV V Ans: B

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Chapter 1

Topic: Lewis Structures, Formal Charges 20. Which compound contains a nitrogen atom with a formal positive charge?H N N N

I

II

III

A) B) C) D) E)

I II III More than one of the above None of the above Ans: D

Topic: Lewis Structures 21. Considering Lewis structures, which of these compounds possesses a single unpaired electron? A) N2 B) N2O C) NO D) N2O4 E) O2 Ans: C Topic: Lewis Structures 22.Y..

Z

..

Y is a generalized structural representation which can be used for all of the

A) B) C) D) E)

following, except: OF2 NH2 H2S BeBr2 There is no exception Ans: D

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Chapter 1

Topic: Lewis Structures, Formal Charges 23. In which of these cases does the central atom have a zero formal charge? A) HFH H B) C)H3C O FF B F F

CH3

D)H3C

H N CH3

E)H3C

H CH3C CH3

CH3

Ans: E Topic: Lewis Structures, Formal Charges 24. The formal charge on sulfur in sulfuric acid is:O H O S O O H

A) B) C) D) E)

0 -1 +1 -2 +2 Ans: A

Topic: Lewis Structures, Formal Charges 25. ExpAns:ion of the valence shell to accommodate more than eight electrons is possible with: A) Fluorine B) Nitrogen C) Carbon D) Sulfur E) Beryllium Ans: D

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Chapter 1

Topic: Lewis Structures, Molecular Geometry 26. A) B) C) D) E) Based on VSEPR theory, which of the following would have a trigonal planar shape? CH3)3N HCN NH4+ CH3 CH3+ Ans: E

Topic: Lewis Structures, Molecular Geometry 27. A) B) C) D) E) VSEPR theory predicts an identical shape for all of the following, except: NH3 H3O+ BH3 CH3All have the same geometry Ans: C

Topic: Lewis Structures, Molecular Geometry 28. A) B) C) D) E) What shape does the methyl cation, CH3+, have? Octahedral Tetrahedral Trigonal planar Linear Trigonal pyramidal Ans: C

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Chapter 1

Topic: Lewis Structures, Molecular Geometry 29. Which of the structures below would be trigonal planar (a planar triangle)? (Electrical charges have been deliberately omitted.) F F H .. .. .. .. .. .. :F : N : H:O:H H:C: B :..: .. .. .. .. .. F H F F H: : II

.. ..

.. ..

.. : ..

.. : ..

II

III

IV

A) B) C) D) E)

I II III IV I and IV Ans: A

Topic: Lewis Structures, Molecular Geometry 30. Which of the following would have a trigonal planar (or triangular) structure?: CH3 : CH3 II : NH3 III BH3 IV : OH3 V

A) B) C) D) E)

I, II, and IV II and IV IV II, IV, and V All of these Ans: B

Topic: Molecular Geometry 31. A) B) C) D) E) What bond angle is associated with a tetrahedral molecule? 120 109.5 180 90 45 Ans: B

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Chapter 1

Topic: Molecular Geometry 32. A) B) C) D) E) What would be the spatial arrangement of the atoms of the methyl anion, :CH3-? Octahedral Tetrahedral Trigonal planar Linear Trigonal pyramidal Ans: E

Topic: Lewis Structures, Molecular Geometry 33. A) B) C) D) E) Which of these structures would be a perfectly regular tetrahedron? CH3Br CH2Br2 CHBr3 CBr4 More than one of these Ans: D

Topic: Lewis Structures, Molecular Geometry 34. Which molecule would be linear? (In each case you should write a Lewis structure before deciding.) A) SO2 B) HCN C) H2O2 D) H2S E) OF2 Ans: B Topic: Lewis Structures, Molecular Geometry 35. A) B) C) D) E) The bond angles in PH3 would be expected to be approximately: 60 90 105 109 120 Ans: C

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Chapter 1

Topic: Periodic Properties, Electronegativity 36. A) B) C) D) E) Select the most electronegative element. H O N B C Ans: N

Topic: Atomic Orbitals, Hybridization 37. Select the hybridized atomic orbital.

IA) B) C) D) E) I II III IV V Ans: C

II

III

IV

V

Topic: Atomic Orbitals, Hybridization 38. How many 2p atomic orbitals from boron must be mixed with a 2s atomic orbital to yield the bonding hybrid atomic orbitals in BF3? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: B

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Chapter 1

Topic: Atomic Orbitals, Hybridization 39. A) B) C) D) E) In which molecule is the central atom sp3 hybridized? CH4 NH3 H2O All of these None of these Ans: D

Topic: Atomic Orbitals, Hybridiz