Practice%20Exam%201B - Practice Exam 1B 1 What is the best...

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?

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