Download chem 111 practice exam

Tear off this top page (pg. 1)-It is
your scratch paper
The following are molar masses you may or may not need:
H2O = 18.02
SO2 = 64.06
AgCl = 143.4
NaCl = 58.49
KCl = 75.35
KClO3 = 123.35
CO2 = 44.01
KCl = 58.0
Na2S2O3 = 158.1
Na2SO3 = 126.1
CO32-- =
NH3 = 17.03
CH4 = 60.01
HCN = 27.02
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CHE M. 111
Fall 2004
CLS
EXAM I
NAME________________
last
______________
first
THERE ARE 6 PAGES TO THIS EXAM (including the cover page) Significant Figures must be correct. All set-ups
must be shown (where applicable) or you will receive no credit.
(10 points) 1. Myoglobin stores oxygen for metabolic processes in muscle. Chemical analysis shows that it
contains 0.34 % Fe by mass. If there is one Fe atom per molecule of myoglobin, what is the molar
mass of myoglobin.
ANSWER________________________
(12 points) 2. By analysis a compound with the formula Na2Al(OH)x is found to contain 17.11 % Al. Calculate
the interger X
ANSWER________________________
Page 2
(13 points) 3 . A mixture of C and NaCl is heated in oxygen. The C in the mixture reacts to form 21.5 g CO2
according to the following reaction: C + O2 Æ CO2 (g) Then what remains is dissolved in water and an excess
amount of AgNO3 is added and reacts with the chloride to form 25.12 g AgCl. Calculate the % C in the mixture.
ANSWER________________________
(15 points) 4. A sample contains a mixture of KCl and KClO3 . KClO3 decomposes by the following reaction:
KClO3 Æ KCl + O2
If at the end of the reaction, 43.44 g of KCl are present and 3.22 g of O 2 are formed, calculate
how many grams of original mixture (KCl and KClO3 ) present before the reaction.
ANSWER________________________
Page 3
(18 points) 5. Lysine, an essential amino acid in the human body, contains C, H, O, and N. In one experiment, the
complete combustion of 2.175 g of lysine gave 3.94 g CO2 and 1.89 g of H2O. In a separate
experiment, 1.873 g of lysine gave 0.436 g NH3. Calculate the molecular formula of lysine if the
approximate molar mass of lysine is 150.
ANSWER________________________
Page 4
(15 points) 6. A mixture of Na2SO3 and Na2S2O3 is dissolved in water and reacted with HCl (aq).
Na2SO3 + 2 HCl ---> 2 NaCl + SO2 + H2O
Na2S2O3 + 2 HCl ---> 2 NaCl + SO2 + S + H2O
The reactions yield 4.49 g of S and 30.1 g of SO2. What percentage of the mixture is Na2SO3?
ANSWER_______________________
(12 points) 7. Suppose that a metal, X, forms a solid carbonate with the formula X(CO3)2 and the oxide
decomposes to form carbon dioxide and a metal oxide.
a) A 6.3180 g sample of X(CO3)2 forms 2.330 g CO2, calculate the molar mass of “X”
b) What is the identity of metal “X”
\
ANSWER________________________
Page 5
(15 points) 8. Hydrogen cyanide is prepared from ammonia, air, and natural gas, CH4 by the :
2 NH3 + 3 O2 +2CH4---> 2HCN + 6 H2O
If a reaction vessel contains 1.15 g NH3, 1.00 g oxygen, and 1.05 g CH4 produces 0 .400 g HCN, what is the percent
yield for the reaction?
ANSWER________________________
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