Unformatted text preview: 1 Chemistry 102 Practice Midterm ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Last Name (please print) ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ Signature ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ First Name ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ID Number Instructions: 1. This exam has 5 questions. Make sure you have a complete exam and write your name on pages detached from the exam. 2. This is a closed-book examination. 3. Place your answers on the FRONT SIDE of each page and CLEARLY NOTE any work on the back side of a page. 4. Exams written in pencil are not eligible for re-grading. 5. You may use any approved calculators. Problem 1 2 3 4 5 Total Maximum mark 10 8 9 8 8 Mark received 2 1. (8 marks) (a) (3 marks) Determine if the following substances yield acidic, basic or neutral aqueous solutions: Lithium hypochlorite:_____________ NH4F : [CH3NH3]CN : ______________ _______________ (b) (2 marks) Write the dominant acid/base equilibrium reaction for each of the following solutions: A solution was produced from adding NaClO2 (s) to water: A 1.0 M solution of HCN (aq) is treated with an equal volume of 1.0 M NaOH (aq): (c) (3 marks) Using the information for these reactions at 500 oC: 1) 2 NO2 (g) ↔ 2 NO (g) + O2 (g) K = 1.95 × 10-5 2) 3) 2 N2O (g) ↔ 2 NO (g) + N2 (g) 2 NO2 (g) ↔ N2O4 (g) K = 192.35 K=4 determine the equilibrium constant for this reaction also at 500 oC: 4) 2 N2O (g) + O2 (g) ↔ 2 NO2 (g) + N2 (g) 3 2. (9 marks) At 373 K, a reaction for the production of chlorine gas is: 4 HCl (g) + O2 (g) ↔ 2 H2O (g) + 2 Cl2 (g) K = 1.96 × 109 Determine the equilibrium partial pressure of all gases at 373 K, from the initial conditions of: PHCl = 0.5 atm PO2 = 0.1 atm PH2O = 0.1 atm PCl2 = 0.2 atm 4 3. (a) (6 marks) You want to make a buffer of pH = 7.0, how much 0.20 M NaOH is needed if you have 250.0 mL solution of 0.40 M acetic acid? (b) (2 marks) How much NaOH is required to completely convert the initial acetic acid solution to acetate? 5 4. (8 marks) What is the concentration of Fe3+ ions in solution at equilibrium after 100mL of a 0.080 M solution of FeCl3 has reacted with 100 mL of a 0.030 M solution of NaOH? (Ksp=4.0×10-38 for Fe(OH)3) 6 5. (a) (5 marks) Calculate the solubility of MgF2 (Ksp=6.4×10-9) in a 0.10 M solution of NaF. (b) (2 marks) CaF2 has a Ksp value of 4.0×10-11 in water at 25oC. Would you expect CaF2 to be more or less soluble than MgF2 in water? Justify your answer. (c) (3 marks) In water at 25oC, MgF2 has a solubility of 1.2×10-3 M. Would you expect the solubility to increase, decrease or not change if water was replaced with a 0.01 M solution of: i) KCl ii) KF iii) MgCl2 i) ii) iii) ...
View Full Document
This note was uploaded on 03/25/2009 for the course CHEM 102 taught by Professor Drk during the Spring '09 term at University of Alberta.
- Spring '09