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Practice%20Exam%201B

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

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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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