Download Exam 3 Review - CHEMpossible

CHEMpossible
Exam 3 Review
1. In the combustion of methane (CH4), what change in hybridization (if any) occurs to the carbon
atom?
a. sp2 to sp3
b. sp2 to sp
c. sp3 to sp2
d. sp3 to sp
e. no change in hybridization occurs
2. Which statement is true regarding bond order, bond length, and bond energy?
a. As the bond order increases, the bond length increases.
b. As the bond order increases, the bond length decreases.
c. As the bond order increases, the bond energy decreases.
d. As the bond energy increases, the bond length increases.
e. As the bond energy increases, the bond order decreases.
3. Circle each statement that applies to thermal energy and heat:
a. Thermal energy is the average kinetic energy of its molecules due to their motion
b. High thermal energy is reflected in a high temperature of the substance
c. Thermal energy is transferred in the form of heat from areas of low kinetic energy to
high kinetic energy
d. Molecular collisions is how thermal energy is transferred
4. According to VSEPR theory, repulsive forces decrease in what order?
a. Lone-pair vs. lone-pair > lone-pair vs. bonding pair > bonding-pair vs. bonding-pair
b. Lone-pair vs. bonding pair > bonding pair vs. bonding pair > lone-pair vs. lone-pair
c. Bonding-pair vs. bonding-pair > lone-pair vs. lone-pair > bonding-pair vs. lone-pair
d. Bonding-pair vs. bonding-pair > lone-pair vs. bonding-pair > lone-pair vs. lone-pair
5. In carbon-hydrogen-oxygen compounds
a. All oxygen-hydrogen bonds are pi bonds
b. All carbon-hydrogen bonds are sigma bonds
c. All carbon-carbon bonds are pi bonds
d. All carbon-carbon bonds consist of a sigma and one or more pi bonds
6. In which of the following molecules is the nitrogen-to-nitrogen bond distance expected to be
the shortest?
a. N2H4
b. N2
c. N2O4
d. N2O
7. Which of the following contains the most moles of solute?
a. 200 mL of 0.250 M NaCl
b. 500 mL of 0.125 M Na2SO4
c. 150 mL of 0.300 M KBr
d. 750 mL of 0.075 M MgCl2
8. In assigning oxidation numbers, which of the following does NOT apply:
a. The oxidation state of H is always +1 except when combined with metals
b. The oxidation state of free elements is 0
c. The oxidation state of oxygen is usually -2
d. The sum of all the oxidation numbers for an ion is 0
9. Consider two solutions: 0.10 M solution of LiBr and a 0.10 M solution of KCN. Which of the
following statements does NOT describe both of these solutions?
a. Both solutions are homogeneous.
b. Ion-dipole attractions played an important role in forming these solutions.
c. Both solutions contain the same number of moles of solute.
d. Both solutions will conduct electricity.
10. The limiting reagent in a reaction is the one that:
a. has the smallest molar mass.
b. has the largest molar mass.
c. has the smallest stoichiometric coefficient.
d. is in excess.
e. determines the theoretical yield.
11. Aspirin can be made in the lab by reacting acetic anhydride (C4H6O3) with salicyclic acid (C7H6O3)
to form aspirin (C9H8O4). The balanced equation is:
C4H6O3 + C7H6O3 
C9H8O4
+
C2H4O2
In the synthesis, a student begins with 3.00 mL of acetic anhydride (density = 1.08 g/mL) and
1.25 g of salicyclic acid. Once the reaction is complete, the student collects 1.22 g of aspirin.
Determine the limiting reagent, theoretical yield of aspirin, and percent yield for the reaction.
12. Answer the following for the reaction:
NiCl2 (aq)
+ 2NaOH (aq)

Ni(OH)2 (s)
+
2NaCl (aq)
a. How many milliliters of a 0.200 M NaOH solution are needed to reaction with 18.0 mL of
a 0.500 M NiCl2 solution?
b. How many grams of Ni(OH)2 are produced from the reaction of 35.0 mL of a 1.75 M
NaOH solution and excess NiCl2?
c. What is the molarity of 30.0 mL of a NiCl2 solution that reacts completely with 10.0 mL
of a 0.250 M NaOH solution?
13. Pyridinium chlorochromate (PCC) is frequently used to convert carbon-oxygen single bonds
(alcohols) to carbon-oxygen double bonds (aldehydes and ketones).
a.
b.
c.
d.
e.
Draw the Lewis Structure for the two chromium reagents above.
How did the carbon-oxygen bond length, strength, and order change going from A to B?
What is the oxidation number of Cr in both reagents above?
Did any changes in hybridization occur in going from A to B?
What is the electron domain geometry and molecular shape of both Cr reagents?
14. How many atoms of aluminum are in a sample that absorbs 8.80 kJ of energy when heated from
12.5 °C to 26.8 °C? (c = 0.897 J/g·°C)