1
Practice Exam 1B
1. What is the best answer to report for
3478
1164
200
0354
.
.
.
.
?
×
+
(A) 2.378
(B) 2.3782
(C) 2
(D) 2.4
(E) 2.38
2.
The density of a gas is 1.96 g/L at 1.00 atm and 0 °C. What is the density of this gas at 0.855
atm and 25.0 °C ?
3.
A sheet of Xerox paper measures 8.5
×
11.0 inches. What is the surface area of one side
of the paper in cm
2
?
4.
You are given a 0.252 g sample of a copper-containing alloy and asked to determine the
weight percent of copper. After dissolving the metal in acid, you add an excess of KI, and
the Cu
2+
and I
-
ions undergo the reaction
2Cu
2+
(aq) + 5I
-
(aq)
Æ
CuI(s) + I
3
-
(aq)
The liberated I
3
-
is titrated with sodium thiosulfate according to the equation
I
3
-
(aq) + 2S
2
O
3
2-
(aq)
Æ
S
4
O
6
2-
(aq) + 3I
-
(aq)
If 26.32 mL of 0.101 M Na
2
S
2
O
3
is required for titration to the equivalence point, what is the
weight percent of Cu in the alloy?
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2
5. A 1.00 g sample of KMnO
4
(M = 158 g/mol) was completely decomposed by heating, yielding
99.2 mL of oxygen collected over water at 22
o
C and a total pressure of 755 mmHg. At 22
o
C the
vapor pressure of water is 20 mm Hg. Which of the following equations best fits this data for the
decomposition reaction?
(A)
2KMnO
4
(s)
Æ
K
2
MnO
4
(s) + MnO
2
(s) + O
2
(g)
(B)
2KMnO
4
(s)
Æ
K
2
MnO
3
(s) + MnO(s) + 2O
2
(g)
(C)
7KMnO
4
(s)
Æ
3K
2
MnO
4
(s) + Mn
3
O
4
(s) + 6O
2
(g)
(D)
8KMnO
4
(s)
Æ
4K
2
MnO
4
(s) + 2Mn
2
O
3
(s) + 5O
2
(g)
(E)
9KMnO
4
(s)
Æ
3K
3
MnO

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- Spring '10
- mr
- Enthalpy, Standard enthalpy change of formation
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