CHM 1046 PRE-TEST 3 July 3, 1996 This test is take-home and open book, and it is intended that all members of the group contribute to completing it. Only one copy is to be submitted by the group, and all members who participated should sign their names below. Test is due at the beginning of class on Monday, July 8. (You may take values of Ka, Ksp, and Kf from tables in the textbook. These figures will be provided on the hour test). List names in alphabetical order! _______________________ _______________________ _______________________ _______________________ _______________________ _______________________ Points 1. Determine the pH of the following solutions: (7) (a) 2.63 g of Ca(OH)2 is dissolved in enough water to make 1.00 L of solution. (7) (b) 0.250 L of 0.200 M HCl solution is added to the Ca(OH)2 solution in part 1(a). (7) (c) How many L of 0.200 M HCl solution would have to be added to the Ca(OH)2 solution in part 1(a) to produce a pH of 7.0? 2. Determine the pH of the following solutions: (8) (a) 2.63 grams of sodium acetate is added to enough water to make 1.00 L of solution. (8) (b) 0.100 L of 0.200 M HCl solution is added to the solution of sodium acetate in part 2(a) above. (8) (c) 0.100 L of 0.200 M acetic acid solution is added to the solution of sodium acetate in part (a) above. (5)3. What is the [HCO3-]/[H2CO3] ratio in blood at pH 7.40? (8)4. You have made a buffer of formic acid at pH 3.00 in which the total formic acid + formate concentration ([HCOOH] + [HCOO-] is equal to 0.0500 M. What are the concentrations of [HCOOH] and [HCOO-]? 5. How many grams of barium sulfate will dissolve in: (5) (a) 1.00 L of water? (5) (b) 1.00 L of 0.050 M Na2SO4 salt solution? (6)6. What is the pH of a saturated solution of Mn(OH)2? (6)7. Calculate the equilibrium constant for the following reaction: CuCO3(s) + 4 NH3(aq) ----> Cu(NH3)42+ + CO32- (6)8. For the reaction: CH4(g) + 2 O2(g) ----> CO2(g) + 2 H2O(g) The initial rate of change of [CH4] is -0.15 Ms-1. Give the initial rate of change of: [O2] ________ [CO2] ________ [H2O] ________ (6)9. The rate law for the following reaction is first order in H2 and second order in NO, with a rate constant k at 1000 K of 6.0 X 104 M-2s-1. 2 NO(g) + 2 H2(g) ----> N2(g) + 2 H2O(g) What is the rate of the reaction under the following conditions? [H2] [NO] rate 0.055 M 0.012 M _______________________ 0.110 M 0.012 M _______________________ 0.055 M 0.024 M _______________________ (8)10.The decomposition of hydrogen peroxide to water and oxygen follows a first order rate law in H2O2 with a half-life of 18 min. 2 H2O2(l) -----> H2O(l) + O2(g) (a) What is the rate constant k for the reaction? (b) Starting with a solution that is 0.500 M in hydrogen peroxide, what will be the hydrogen peroxide concentration after 60 min?