Name
CHM 115 EXAM #3
Practice
Complete the following showing all of your work. When calculations are required, show the set-up, units,
and report answers with the correct number of significant figures. Short answers should be composed of
well-organized thoughts and written in full sentences.
(20 points for completion of BOTH parts (a) and (b))
1.
(a) In the spaces provided, do the following for BrF5
Draw the BEST Lewis structure of this interhalogen
molecule and show formal charge calculations for
each type of atom
Give the names of (a) the electron pair
geometry and (b) the molecular shape,
(a)
(b)
Specify the hybridization of the Br AND
draw the energy diagram for the hybridized orbitals
(you know - the boxes with electrons in them).
Is this species polar or nonpolar? Explain.
(b) In the spaces provided, do the following BrF3
Draw the BEST Lewis structure of this interhalogne
molecule and show formal charge calculations for
each type of atom
Give the names of (a) the electron pair
geometry and (b) the molecular shape,
(a)
(b)
Specify the hybridization of the Br AND
draw the energy diagram for the hybridized orbitals
(you know - the boxes with electrons in them).
Is this species polar or nonpolar? Explain.
(20 points)
2.
For the following two species complete the tasks specified below in a - d.
i. CH3COOH
ii. C2H2
a. Draw the best Lewis
structures.
b. Specify the hybridization
of both
the C atoms and the O atom
specified in (i)
and the C atoms in (ii)?
C in CH3
C in CH
C in CO
O between CO and H
c. Show the energy level
diagram for both the C atoms
and the O atom in (i) and the
C atoms in (ii), fill the
diagrams with the correct
number of valence electrons,
and identify the types of
electrons present (i.e. σ, π,
lone pair)
C in CH3
C in CH
C in CO
O between CO and H
d. What are the bond angles
around both the C atoms and
the O atom in (i) and the C
atoms in (ii)?
C in CH3
C in CH
C in CO
O between CO and H
(10 points)
3. Reaction of solid white phosphorus (P4) with chlorine gas (Cl2) yields phosphorus trichloride as
the sole product at 100 % yield. (a) Write a balanced chemical equation.
(b) When 1.00 g of solid white phosphorus (P4) is reacted with excess chlorine gas (Cl2),
determine the maximum amount of PCl3 that can be formed?
2
4.
(20 points)
Fill in the MO energy diagrams for the species listed below. The answer the questions that appear
under the MO energy diagram of each species.
nitrogen
Ν
pernitride
2
σ∗2p
Ν
−2
2
σ∗2p
π∗2p
π∗2p
π∗2p
π∗2p
π2p
π2p
π2p
π2p
σ2p
σ2p
σ∗2s
σ∗2s
σ2s
σ2s
σ*1s
σ*1s
σ1s
σ1s
Show the calculation of the bond order for
nitrogen.
Show the calculation of the bond order for the
above ion.
Is nitrogen diamagnetic or paramagnetic?
Explain your answer.
Is the above ion diamagnetic or paramagnetic?
Explain your answer.
Draw the Lewis structure of nitrogen.
Draw the Lewis structure for the above ion.
Does the bond order for nitrogen from the
Lewis structure match the bond order from
the MO diagram?
Does the bond order for the above ion from the
Lewis structure match the bond order from the
MO diagram?
Which should have the longer, weaker bond; nitrogen or the above ion? Explain your choice!
3
(12 points)
5.
C4H10 (g) +
O2 (g)
à
CO2 (g) +
H2O (l)
a. Balance the reaction above.
b. If 25.0 g of C4H10 reacts with 100.0 g of O2, how much CO2 (in BOTH moles and
grams) can be formed? Show which reactant is the limiting reactant!!
c. If the dry CO2 is collected and has a mass of 74.6 g, what is the % yield?
(8 points)
6.
Balance the following redox reaction in acidic solution.
I
(aq)
+
MnO4
(aq)
→
I2 (aq) +
Mn2+ (aq)
(7 points)
7.
A 5.00 mL sample of battery acid [H2SO4 (aq)] is completely neutralized (converted to
aqueous sodium sulfate and water) by 45.60 mL of 0.9995 M sodium hydroxide [NaOH
(aq)]. Complete and balance the reaction and calculate the molarity of the original 5.00
mL H2SO4 (aq) sample. By calculation, demonstrate that the acid in the optimal
concentration range (between 4.3 – 5.0 M)
H2SO4 (aq)
+
NaOH (aq)
→
4
BONUS: for up to 6 points (total)
Write the products for the reactions listed below and make sure the reactions are balanced
molecular (that is total) equations. Also, name the type of reaction (oxidation-reduction,
acid-base neutralization, or precipitation) in the blank to the right .
(2 points each)
a.
Ba (s)
+
O2 (g)
b.
HCl (aq) + Ba(OH)2 (aq) →
c.
AlCl3 (aq) + AgNO3 (aq) →
→
5