Answers have not been double checked!!!
Chemistry 151 Quiz 2 - 1
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) Which element has the largest electronegativity?
(a)
2.
N
(c)
O
(d)
C
H2O
(b)
CO2
(c)
NH3
(d)
XeF4
(4 pts) Which statement about the combustion of Mg(s ) in air is correct?
(a)
(b)
(c)
(d)
4.
(B)
(4 pts) Which molecule contains NO unshared pairs of electrons on the central atom?
(a)
3.
B
The
The
The
The
white smoke that appeared during combustion was MgCO3(s ).
demonstration showed that the combustion process is endothermic.
electron affinity for the process ½O2(g ) + 2 e → O2-(g ) is exothermic.
reaction was exceedingly energetic because of the large magnesium oxide lattice energy.
(3 pts) In which list are the three ionic compounds arranged in order of INCREASING (least first) lattice
energy.
(a)
(b)
LiBr < LiF < MgO
MgO < LiF < LiBr
(c)
(d)
MgO < LiBr < LiF
LiBr < MgO < LiF
Chemistry 151 Quiz 2 - 2
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) Which molecule/ion has three (3) unshared pairs of electrons on the central atom?
(a)
ICl21-
(b)
PF61-
(c)
NO21-
(d)
SO3
2.
(4 pts) In the space at the right of the answer sheet draw resonance structures for ozone, O3(g).
3.
(4 pts) The electronegativity of phosphorus is 2.1; that of Cl is 3.0.
Calculate the partial charge, δ, on phosphorus in the molecule PCl3 and write it at the right of the answer
sheet.
δP = 5 - 2 - 6(2.1/5.1) = +0.53
4.
(3 pts) In which molecule do we expect the bond to be non-polar?
(a)
HCl
(b)
CO
(c)
N2
(d)
NO
Chemistry 151 Quiz 2 - 3
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) In which of the following molecules do we expect the bond length to be shortest?
(a)
O2
(b)
NO
(c)
CO
(d)
F2
(c)
COCl2
(d)
SF4
In CO the bond order is 3.
2.
(4 pts) Which molecule will be non-polar?
(a)
SO2
(b)
BF3
The molecule is trigonal planar and the polar B-F bonds cancel.
3.
(3 pts) What is the electron pair geometry of the central atom in PH3?
(a)
(b)
4.
trigonal planar
tetrahedral
(c)
(d)
see-saw
square planar
(4 pts) Which statement about the demonstration in which Li, Na, and K were added to water is
CORRECT?
(a)
(b)
(c)
(d)
The indicator phenolphthalein is pink in a basic solution.
These metals are very hard.
These metals must be protected from moisture, but not from oxygen.
The metal with the fewest electrons, Li, reacted most rapidly.
Chemistry 151 Quiz 2 - 4
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) In the space at the right of the answer sheet draw the Lewis structure of the ion, SO32-.
Structure drawn has formal charge of zero on S; resonance structures are
possible.
2.
(4 pts) Consider the properties listed below, then identify the correct answer.
(1)
(2)
(3)
(4)
(a)
(b)
(c)
(d)
3.
All four properties describe an ionic compound.
Only properties (1), (2), and (4) describe an ionic compound.
Only properties (2) and (4) describe an ionic compound.
Only property (4) describes an ionic compound.
(4 pts) Which molecule is polar?
(a)
4.
Dissolve in non-polar solvents.
Aqueous solutions conduct electricity.
Melting point below 300°C.
Very hard.
SO3
(b)
NH3
(c)
CO2
(d)
SiCl4
(3 pts) Identify the INCORRECT statement about the demonstrations.
(a)
(b)
(c)
(d)
Dry NI3 NH3 detonates when touched.
In NI3 NH3 four iodine atoms surround the N atom.
NI3 NH3, an ionic compound, detonates because of the large lattice energy.
The N≡N bond is a very strong bond.
It’s a molecular compound.
Chemistry 151 Quiz 2 - 5
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) What is the bond order of the C-N bond in CN1-?
(a)
2.
(b)
2
(c)
2.5
(d)
3
(4 pts) Which statement is CORRECT?
(a)
(b)
(c)
(d)
3.
1
Gaseous chlorine can be prepared by heating a MnO2(s)-HCl(aq) solution.
The N-I bonds in NI3 NH3 can be broken by a photoflash.
Bromine is slightly soluble in water, so it must be a polar molecule.
The H-H bond in H2 is easily broken by visible light.
(3 pts) The molecular geometry of the ion, IF41- is
(a)
square pyramidal
(c)
trigonal pyramidal
(b)
octahedral
(d)
see saw
No correct answer. Molecular geometry is square planar; electron pair geometry is octahedral.
4.
(4 pts) Calculate the partial charge on the P atom in the molecule PCl3 and write it in the space at the right
of the answer sheet. The electronegativities of P and Cl are 2.6 and 3.0, respectively.
δP = 5 - 2 - 6(2.6/5.6) = + 0.21
Chemistry 151 Quiz 2 - 6
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) In which compound do we expect the ionic bond to be strongest?
(a)
2.
(d)
LiF
(c)
MgF2
(d)
NaClO3
the H-H bond is easily broken, producing H atoms that react with chlorine.
the flash ionizes hydrogen, producing a proton, which then combines with the chlorine gas.
the Cl-Cl bond is broken by the photoflash and Cl atoms react with H2, producing HCl and H
atoms and causing a chain reaction.
of the very large H-Cl lattice energy.
(3 pts) In which list are the atoms arranged in order of increasing (smallest first) electronegativity?
(a)
(b)
(c)
(d)
4.
(b)
(4 pts) H2 reacts explosively with Cl2 when the mixture is exposed to a bright light because
(a)
(b)
(c)
3.
CaO
F < P < Al < Mg
Mg < Al < P < F
Al < Mg < P < F
F < P < Mg < Al
(4 pts) The molecular geometry of the ion, NO21- is
(a)
(b)
(c)
(d)
trigonal planar.
linear.
bent.
trigonal pyramidal.
Chemistry 151 Quiz 2 - 7
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) Which molecule/ion will be polar?
(a)
CH4
(b)
I31-
(c)
SCl2
(d)
XeF4
SCl2 is polar because it is bent and has two unshared pairs of electrons.
2.
(3 pts) In which list are the elements arranged in order of increasing electronegativity (lowest value first)?
(a)
(b)
(c)
(d)
3.
(4 pts) Which statement about the demonstration in which Li, Na, and K were added to water is
CORRECT?
(a)
(b)
(c)
(d)
4.
Cl < Ga < Mg < Sr
Mg < Ga < Sr < Cl
Sr < Mg < Ga < Cl
Ga < Sr < Cl < Mg
The indicator phenolphthalein is colorless in a basic solution.
K reacted more rapidly than Na, consistent with its higher electron affinity.
Li reacted least rapidly, consistent with it having the highest 1st ionization energy.
The metals react rapidly with moisture, but do not react with oxygen in the air.
(4 pts) What is the electron pair geometry of the ion, SnCl31-?
(a)
(b)
(c)
(d)
tetrahedral
trigonal planar
trigonal bipyramidal
trigonal pyramidal
Chemistry 151 Quiz 2 - 8
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) Which molecule/ion does not have a resonance structure?
(a)
2.
NO31-
(b)
SO3
(c)
CO32-
(d)
CO2
(4 pts) The molecular geometry of BrF3 is
(a)
(b)
(c)
(d)
trigonal bipyramidal.
T-shaped.
seesaw.
trigonal pyramidal.
3.
(3 pts) In the space at the right of the answer sheet sketch a Lewis structure of POCl3 in which the formal
charge on each atom is zero (0).
4.
(4 pts) Which statement about the demonstrations is CORRECT?
(a)
(b)
(c)
(d)
NI3 NH3 exploded when a photoflash was set off near it.
The H2(g)-Cl2(g) reaction was explosive because energy from a
photoflash dissociated H2 molecules into atoms which then reacted with
chlorine molecules.
Products of the NI3 NH3 explosion were gaseous N2, I2 and presumably
NH3.
The H2(g)-Cl2(g) reaction mixture was prepared by the reaction of MnO2(s) with warm HCl(aq).
Chemistry 151 Quiz 2 - 9
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
(4 pts) What is the molecular geometry of the NH3 molecule?
(a)
(b)
(c)
(d)
2.
trigonal pyramidal.
trigonal planar.
trigonal bipyramidal.
tetrahedral.
(4 pts) The molecules SiCl4, POCl3, and SCl2 all have tetrahedral electron pair geometries. Which
statement about the Cl-E-Cl bond angles, where E represents the central element, is CORRECT?
(a)
(b)
(c)
(d)
The
The
The
The
bond angles will all be the same, about 109°.
Cl-Si-Cl bond angle will be the largest.
Cl-P-Cl bond angle will be the largest.
Cl-S-Cl bond angle will be the largest.
The bond angles will all be about 109° because the electron pair geometry is tetrahedral. However, if we
consider the effect of unshared pairs occupying greater space than shared pairs, we note that the Cl-S-Cl
bond will be closed, or less than 109. Since a double bond occupies more space than a single bond the
Cl-P-Cl bond will also be slightly closed. The Cl-Si-Cl bond will have the optimum tetrahedral angle, and
will be slightly larger than either of the other two angles.
3.
(3 pts) Which molecule is expected to be non-polar?
(a)
4.
H2O
(b)
HF
(c)
ClF
(d)
SF6
(4 pts) Which statement about the structures of NO21- is CORRECT.
(a)
(b)
(c)
(d)
The two N-O bond lengths in NO21- are unequal.
In NO21- a pair of electrons oscillates between the two N-O bonds,
so resonance structures must be drawn.
The N-O bond in NO21- is stronger than a single bond, but not as strong as a double bond.
The N atom has a different formal charge in these resonance structures.
Chemistry 151 Quiz 2 - 10
Week starting Sept. 17, 1997
ENCODE AND WRITE YOUR PID AND NAME ON THE SCANTRON SHEET NOW.
NO ENCODED PID = NO GRADE
Answer all questions on the Scantron sheet. For multiple choice questions please encode the letter of the one best
answer.
1.
2.
(4 pts) Consider the reactions which relate to the demonstration on the burning of Mg in air. Identify the
CORRECT statement. (Endothermic ≡ requires energy.)
(1)
½O2(g )
+
e
→
O1-(g )
(2)
O1-(g )
+
e
→
O2-(g )
(3)
Mg(s )
→
Mg(g )
(a)
(b)
(c)
(d)
Reactions (2) and (3) are endothermic; reaction (1) is exothermic.
All three reactions are exothermic.
All three reactions are endothermic.
Reactions (1) and (2) are exothermic; reaction (3) is endothermic.
(3 pts) In which diagram are the partial charges on the HCl molecule correct?
(a)
3.
(b)
Hδ-Clδ+
(c)
Hδ+Cl0 (d)
H0Clδ-
(4 pts) What is the molecular geometry in the ion, BrCl21-?
(a)
(b)
(c)
(d)
4.
Hδ+Clδ-
trigonal bipyramidal.
T-shaped.
bent.
linear.
(4 pts) Which molecule is non-polar?
(a)
SO2
(b)
O3
(c)
SO3
(d)
SO3 is a planar molecule with all S-O bond lengths equal, so it is non-polar.
SF4