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2009Fchem125exam2answers040ri66

2009Fchem125exam2answers040ri66 - Chem 125 Exam#2 Fall 2009...

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Chem. 125 Exam #2 Fall 2009 PART A. (4 Points each) 1. What is the value of a 0.50 in 3 of gold, if a troy ounce is worth $1,000.00? Useful information: density of Au = 19.3 g/cm 3 ; 1 troy ounce (t oz) = 31.1 g; 2.54 cm = 1 in. a. <$1,000 b. Between $1,000 and $2,000 c. Between $2,000 and $4,000 d. Between $4,000 and $5,000 e. >$5,000 2. Which of the following ionic compounds is soluble in water? 3. What precipitate is formed when a solution of silver acetate is mixed with a solution of zinc iodide? 4. 3.50 g ammonium sulfide, (NH 4 ) 2 S, is dissolved in enough water to make 500. mL of 3 3 3 0.5 2.54 19.3 1 $1000 $5,084 $5,100 1 31.1 1 in cm g t oz x x x x in cm g t oz = ( ( ( ( 29 ( 29 ( 29 4 2 4 4 2 2 4 2 4 14.01 1.01 4 2 32.07 68.3 / 3.50 1 / 0.500 0.102 / 0.102 1 68.3 2 0.1025 0.205 MM NH S x x g mol g NH S mol NH S x L mol L M NH S g NH x M + = + + = = = = =
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Chem. 125 Exam #2 Fall 2009 5. The stockroom has 0.650 M H 2 SO 4 . How many milliliters of this acid are required to prepare 250. mL of 0.0425 M sulfuric acid? 6. Approximately how many potassium ions are in 20 mL of 0.44 M potassium phosphate, K 3 PO 4 ? a. 2 x 10 22 b. 5 x 10 21 c. 8 x 10 23 d. 3 x 10 23 e. 50 7. What is the concentration of nitric acid if excess zinc powder is added to75.0 mL of the acid to produce 0.13 moles of hydrogen gas? ( ( ( ( ( 3 3 2 2 2 . Zn s HNO aq Zn NO aq H g + + 8. What is the temperature of an ideal gas where P = 700. torr, n = 0.65 mol, and V = 6.00 L? 2 4 2 4 0.0425 0.25 1000 16.3 1 0.65 mol H SO L L mL x x x mL L mol H SO L = 3 2 3 2 3 3 3 2 0.13 0.26 1 1 0.26 3.47 3.5 0.075 mol HNO mol H x mol HNO mol H mol HNO mol Conentration HNO M HNO L L = = = ( 29( 29 ( 29 700 1 0.921 1 760 0.921 6.00 ; 104 0.65 0.08206 torr atm P x atm torr atm L PV PV nRT T K L atm nR mol mol K = = = = = = 23 3 4 3 4 3 4 3 4 22 22 0.44 6.02 10 0.02 3 1 1 1. : 20 1 . 6 . 10 2 10 mol K PO x K PO L K x x x L mol K PO K PO x x K Note mL sig f n ig io s + + = =
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Chem. 125 Exam #2 Fall 2009
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