Practice_Exam_III - Exam Three Chemistry 121 Name_ Part...

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Page 1/3 Exam Three – Chemistry 121 Name_______________________________ Part One: Multiple Choice (45 points) Choose the best answer for each question. There is only one correct answer. 1. What is the molar mass of ammonium sulfate ( NH 4 ) 2 SO 4 – an important synthetic fertilizer? a. 70.g/mol b. 92 g/mol c. 114 g/mol d. 132 g/mol e. 146 g/mol 2. Given: N 2 + 3H 2 Æ 2NH 3 How many grams of ammonia are produced if 5.0 grams of nitrogen react with unlimited hydrogen? a. 3.o g b. 6.1 g c. 10.0 g d. 12.2 g e. none of these 3. How many sulfur atoms are there in 25g of Al 2 S 3 ? (N A = 6.022 X 10 23 ) a. 1.0 x 10 23 b. 2.0 x 10 23 c. 3.0 x 10 23 d. 4.5 x 10 21 e. 6.0 x 10 21 4. How many moles of iron are contained in 6.09 g of iron? a. 0.0480 moles b. 0.0558 moles c. 0.109 moles d. 0.917 moles 5. What is the percentage of sulfur in copper (I) sulfide, Cu 2 S by mass? a. 20.1% b. 33.5% c. 46.5% d. 79.9% e. 84.3% 6. Analysis of a hydrocarbon showed that it contained 14.4% hydrogen and 85.6% carbon by mass. What is its simplest (empirical) formula?
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Practice_Exam_III - Exam Three Chemistry 121 Name_ Part...

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