EXAM 4
NAME______KEY-answers highlighted_____(1 pt.)
CHEM 1211 VSU
100 points total
Multiple Choice, 3 pts. each
Dr. Gosnell
Nov. 30, 2005
1. According to the Bohr model for the hydrogen atom, the energy necessary to excite an electron from n
= 2 to n = 3 is ________ the energy necessary to excite an electron from n = 4 to n = 5.
Energy levels get closer and n increases.
a) less than
b) greater than
e) either less than or equal to
c) equal to
d) either equal to or greater than
2. The Schrödinger wave equation
a) calculates the position and momentum of an electron at any given time.
b) can be solved to determine the probability of finding an electron in a region of space.
c) proves that energy is equal to mass times the speed of light squared.
d) incorrectly predicts circular orbits of electrons around nuclei.
3. Which of the following statements is INCORRECT?
a) The location and the energy of an electron in an atom can be simultaneously known with certainty.
b) The energies of an atom’s electrons are quantized.
c) Quantum numbers define the energy states and the orbitals available to an electron.
d) Electrons have both wave and particle properties.
4. What type of orbital is designated n = 3, l= 2, ml = -1?
a) 3s
b) 3p
c) 3d
d) 2f
e) 2d
5. All of the following sets of quantum numbers are allowed EXCEPT
a) n = 6, l = 0, ml = +1
d) n = 3, l = 2, ml = +2
b) n = 5, l = 4, ml = 0
e) n = 1, l = 0, ml = 0
c) n = 4, l= 1, ml = -1
6. What is the total number of orbitals having n = 5 and l = 1?
a) 1
b) 2
c) 3
d) 5
7. Which of the following orbitals might have ml = -2?
a) s
b) s and p
c) p and d
d) d or f
e) 10
8. Which of the following diagrams represent p-orbitals?
(I)
a) (I) only
(II)
(IV)
(III)
b) (II) only
c (III) only
d) (IV) only
e) (I) and (II)
9. A ________ is a region of an electron probability density graph where the probability of finding an
electron is zero.
a) nodal surface
b) singularity
c) electron minimum
d) zero point energy
10. The Pauli exclusion principle states that
a) no two electrons in an atom can have the same four quantum numbers.
b) electrons can have either ±½ spins.
c) electrons with opposing spins are attracted to each other.
d) no two electrons in an atom can have the same spin.
e) atoms with no unpaired electrons are diamagnetic.
11. Which of the following statements regarding subshell filling order are CORRECT?
1. Electrons are assigned to the 4s subshell before they are assigned to the 3d subshell.
2. Electrons are assigned to the 4f subshell before they are assigned to the 6s subshell.
3. Electrons are assigned to the 5d subshell before they are assigned to the 6p subshell.
a) 1 only
b) 2 only
c) 3 only
d) 1 and 3
e) 1, 2, and 3
12. Which element has the electron configuration 1s22s22p63s23p4?
a) Mg
b) S
c) Si
d) Se
e) Ga
13. What is the electron configuration for a lead atom?
a) [Xe]6s26p2
b) [Kr]5d106s26p2
c) [Xe]4f145d106s26p2 d) [Xe]5d106s26p2
14. Which element has the following electron configuration?
1s
a) P
b) S
2p
2s
c) O
d) N
e) F
15. In general, atomic radii
a) decrease down a group and remain constant across a period.
b) decrease down a group and increase across a period.
c) increase down a group and increase across a period.
d) increase down a group and remain constant across a period.
e) increase down a group and decrease across a period.
16. Which one of the following statements is INCORRECT?
a) Ionization energy is always a positive value.
b) Ionization energy is the energy required to remove an electron from a gaseous atom.
c) For any element, the second ionization energy is larger than the first ionization energy.
d) Ionization energy decreases across a periodic of the periodic table.
e) Ionization energy decreases down a group of the periodic table
17. The change in energy for the following reaction is referred to as the ________ for fluorine.
F(g) + e- → F-(g)
a) oxidation energy
b) electron affinity
c) electronegativity energy
d) 1st ionization energy
18. A silicon atom has _____ valence electrons.
a) 0
b) 2
c) 4
d) 6
e) 10
19. Which combination of atoms is most likely to produce a compound with ionic bonds?
a) Al and F
b) P and H
c) C and O
d) Si and O
e) S and Br
20. The lattice energy of LiBr is -815 kJ/mol. This energy corresponds to which reaction below?
a) Li(s) + ½ Br2(g) → LiBr(s)
c) Li(g) + Br(g) → LiBr(s)
e) Li+(g) + Br-(g) → LiBr(s)
b) Li(g) + Br(g) → LiBr(g)
d) Li+(aq) + Br-(aq) → LiBr(s)
21. What is the total number of valence electrons in a carbon dioxide molecule?
Carbon has 4; each oxygen has 6
a) 4
b) 8
c) 16
d) 20
e) 22
22. How many lone-pair electrons are on the carbon atom in CO2? Linear, see pg.403
a) 0
b) 1
c) 2
d) 3
e) 4
23. Which of the following is a correct Lewis structure for ozone, O3?
a) 1
b) 2
c) 3
d) 4
e) 5
24. Which of the following are resonance structures for sulfur dioxide, SO2?
a) 1 and 2
b) 2 and 4
c) 3 and 4
d) 1, 2, and 3
e) 2, 3, and 4
25. Which of the following are possible Lewis structures for C2H6O?
H
H
H C H
H
..
C O
..
H
H
H
..
H C O
.. C H
H
H
H H
(2)
(1)
..
H C C O
.. H
H H
(3)
Watch octet rule
a) 1
b) 2
c) 3
d) 2 and 3
e) 1, 2, and 3
26. Which of the following elements is most likely to form a molecular structure that disobeys the octet
rule?
It’s in Row 3
a) Ne
b) S
c) F
d) C
27. Use VSEPR theory to predict the molecular geometry of H3O+.
a) trigonal-pyramidal
b) trigonal-planar
c) bent
d) T-shaped
e) linear
28. What are the bond angles in a molecule designated as AX4E0 (same as AX4)?
a) 109.5
b) 120
c) 109.5 and 120
d) 90 and 120
e) 90 and 180°
29. One resonance structure for thiocyanate ion is drawn below. What is the formal charge on each atom?
a) S = 0, C = -1, N = 0
d) S = 0, C = +2, N = -3
b) S = 0, C = 0, N = -1
e) S = -2, C = +4, N = -3
c) S = -1, C = 0, N = 0
30. Predict which of the following compounds will have the most polar covalent bond(s).
a) HF
b) CBr4
c) H2S
d) NCl3
e) HI
31. In molecules, as bond order increases,
a) both bond length and bond energy increase.
b) both bond length and bond energy decrease.
c) bond length increases and bond energy is unchanged.
d) bond length is unchanged and bond energy increases.
e) bond length decreases and bond energy increases.
32. When heated, azomethane decomposes into nitrogen gas and ethane gas.
CH3N=NCH3(g) → N2(g) + C2H6(g)
Bond Energy
(kJ/mol)
413
305
346
Bond
C-H
C-N
C-C
Bond
N-N
N=N
NN
Bond Energy
(kJ/mol)
163
418
945
Using average bond energies, calculate the enthalpy of reaction.
Bond broken: one N=N
Bonds formed: one C-C
two C-N
one NN
H   bondsBroken   BondsFormed  [(418)  (2x305)]  [346  945]kJ  263kJ
a) -611 kJ
b) -527 kJ
c) -429 kJ
d) -313 kJ
e) -263 kJ
33. Which one of the following molecules is nonpolar?
a) CH3Cl
b)
SO2
c)
BF3
d)
H2O
Bonus Questions
34. Hund’s rule states that the most stable arrangement of electrons (for a ground state electron
configuration)
a) has a filled valence shell of electrons.
b) has two electrons per orbital, each with identical spins.
c) has m values greater than or equal to zero.
d) has the maximum number of unpaired electrons, all with the same spin.
e) has two electrons per orbital, each with opposing spins.
35. How many nodal planes exist for a 2p orbital?
a) 0
b) 1
c) 2
d) 3
e) 4
Write the answer for these questions in the blank space on your SCANTRON. Be sure to number them.
36. l is called the azimuthal quantum number. Give the names for n, ml and ms.
n, principal
ml magnetic
ms spin
37. In two or three sentences at most tell what is meant by effective nuclear charge.
This is the charge felt by a valence electron from the nucleus. The core electrons between the valence
electrons and the nucleus block (shield) some of the pull from the protons in the nucleus. The effective
nuclear charges equals the nuclear charge minus the number of core electrons.
38. Draw the Lewis dot structure for sulfate ion, SO42-.
I copied this picture from the web. Yours should have square brackets with the
Charge as a superscript.