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Unformatted text preview: Chem127 Quiz3A 1 Chem127 Quiz3A 2 R = 0.08206 Latm/molK Chem127 Points Earned Points Possible 15 Quiz3A 3 Name: Quiz 3A
1. (1 point) If the temperature of a sample of gas is decreased at constant volume, the average velocity of the molecules _______ and the average number of collisions with the wall, per unit area, per second_______. A. remains the same, increases B. remains the same, remains the same C. remains the same, decreases D. decreases, decreases E. increases, increases 2. (5 points) How many liters of phosphine (PH3) can form when 32.5g of phosphorous reacts with 86.0L of hydrogen gas react at STP (0C and 1.00 atm, the temperature and pressure are held constant during the reaction). P4 (s) + 6H2 (g) 4PH3 (g) First determine the limiting reactant and then use those moles of phosphine to determine the volume formed:
1 mole 4 moles PH 3 " = 1.05 moles PH 3 123.88 g 1 mole P4 PV = nRT, n = PV/RT (1.00 atm)(86.0L) 4 moles PH 3 nH2 = = 3.84 moles H 2 " = 2.56moles PH 3 (0.08206L atm/mol K)(273K) 6 mole H 2 So, phosphorous is the limiting reactant nRT (1.05moles)(0.08206)(273K) V= = = 23.5L P 1.00atm 32.5 g P4 " ! 23.5L Chem127 Quiz3A 4 3. (3 points) Check () whether each of the following statements is TRUE or FALSE. Read each statement CAREFULLY! Worth 2 points each. Statement put in liquid nitrogen. b. In the "peeps demo", when a vacuum was applied to the container with the peeps, their size increased due to an increase in pressure. c. In a redox reaction, the reducing agent undergoes loss of electrons. True False a. In the gas laws demo, the balloon increased in volume when it was 4. (3 points) For the following reactions, write the chemical formulas for the predicted products. Then, balance the reaction. Please include phase labels for your predicted products. a. Solid magnesium + Aqueous zinc nitrate Mg(NO3)2 (aq) + Zn (s) b. Solid gold + Aqueous silver nitrate NO RXN c. Zn (s) + 2 HCl (aq) ZnCl2(aq) + H2(g) 5. (3 points) For reaction c above, fill in the following table: Reduced Species Oxidized Species Oxidizing Agent H in HCl Zn H in HCl ...
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This note was uploaded on 03/06/2008 for the course CHEM 127 taught by Professor Able during the Spring '08 term at Cal Poly.
- Spring '08