Download Exam II

CHM134. General Chemistry I
Spring 2009: Exam II
Name ______________________________
2pt
1. 15 pts. Balance the following chemical equations:
__ CH4 + __ O2 Æ __ CO2 + __ H2O
__ CuCl2 + __ K2O Æ __ KCl + __ CuO
__ C12H22O11 + __ H2O Æ __ C2H6O + __ CO2
__ NO2 + __ O2 + __ H2O Æ __ HNO3
__ N2O5 + Æ __ NO2 + __ O2
__ Na + __ H2O Æ __ NaOH + __ H2
2. 16 pts. Sulfuric acid dissolves aluminum metal according to the reaction,
2 Al (s) + 3 H2SO4 (aq) Æ Al2(SO4)3 (aq) + 3 H2 (g)
Answer the following:
a. How many moles of sulfuric acid are needed to dissolve 3.0 moles of Al?
b. How many moles of hydrogen gas will form if 1.0 moles of Al dissolve?
c. How many grams of hydrogen gas will evolve if 2.50 grams of Al react?
d. If 2.5 moles of Al are combined with 3.5 moles of sulfuric acid, which is the
limiting reactant?
e. If 100.0 mL of a 0.6000 M sulfuric acid are combined with 10.0 grams of Al,
what is the maximum mass in grams of hydrogen gas that could evolve?
3. 14 pts. Consider the reaction of magnesium with carbon dioxide:
2 Mg(s) + CO2 (s) Æ C(s) + 2 MgO (s)
Molar masses: Mg = 24.30g CO2 = 44.01g C = 12.01g MgO = 40.30g
If 40.0 grams of Mg are combined with 40.0 grams of carbon dioxide, what is the
maximum number of grams of MgO that will form? What is the maximum number
grams of C that can form? How many grams of each reactant would be left?
4. 5 pts. Explain how you would prepare 100.0 mL of a 0.2500M CaCl2 solution using the
solid, volumetric glassware, and water. Be specific in terms of how you would do it.
5. 5 pts. Explain how you would prepare 500.0 mL of a 2.000M HNO3 solution by using a
stock solution of 12.00M HNO3 solution, volumetric glassware, and water. Be specific.
6. 10 pts. Circle the compounds that will not dissolve in water:
CsCl
CaO
MgBr2
KOH
Na2CO3
AgI
Cu3(PO4)2
(NH4)2S
CaSO4
Co(NO3)2
7. 15 pts. Complete and balance each of the following molecular equations. If no reaction
occurs, write NO REACTION.
NH4Cl (aq) +
AgNO3 (aq) Æ
Na2SO4 (aq) +
Pb(NO3)2 (aq) Æ
KCl (aq) +
CuNO3 (aq) Æ
HCl (aq) +
Na2CO3 (aq) Æ
H2SO4 (aq) +
NaOH (aq) Æ
8. 8 pts. Assign oxidation numbers to the underlined atom in each case:
H3AsO4 ____
H2O2 ____
P4 ____
HClO4 ____
NaOH ____
PbCl2 ____
C2H6 ____
NaH ____
9. 10 pts. Identify the oxidizing agent, the reducing agent, the element being oxidized, the
element being reduced, and the number of electrons transferred in this balanced chemical
equation:
6HBr( aq ) + KClO3 (aq) → KCl( aq ) + 3Br2 (l) + 3H2 O(l)
oxidizing agent ______________________
reducing agent ______________________
atom being oxidized _____
atom being reduced _____
# of electrons transferred in the balanced equation _____