Unformatted text preview: 1 CHEM 1140 Name___________________________________ Exam #3 -‐ practice Saunders 1. Write clear, concise definitions for the following chemical terms. You may include equations or examples, but those are not substitutes for a definition! a.) Thermodynamics b.) 2nd Law of Thermodynamics c.) Electrolysis d.) Anode e.) Galvanic Cells 2. Which of the following processes are spontaneous and why? a. salt dissolves in water b. a colorless solution becomes uniform in color after a few drops of dye are added c. iron rusts d. you clean your bedroom 2 3. Iron metal is produced commercially by reducing iron (III) oxide found in iron ore with carbon monoxide in this unbalanced reaction: Fe2O3 (s) + CO (g) Fe (s) + CO2 (g) ΔHf° (kJ/mol)
Fe2O3 (s) -110.5
CO (g) 0
Fe (s) -393.5
a.) Calculate ΔG° for this process at 25 °C. b.) Calculate the equilibrium constant, K, for this process at 25 °C. c.) Is the reaction described above spontaneous, non-spontaneous, or at equilibrium at 25°C? Give the appropriate sign (+/−) associated with each entropy change for the reaction: a.) The sign for ΔSsystem = _________ b.) The sign for ΔSsurroundings = _________ c.) The sign for ΔSuniverse = _________ 3 4. Balance the following redox reaction that occurs in an acidic solution and be sure to show all of your work. CH3OH (aq) + Cr2O72-‐ CH2O (aq) + Cr3+(aq) 5. Write the full, balanced cell reaction and calculate ε°cell for the reaction written in shorthand here: MnO4 – (aq) + F-‐ (aq) F2 (g) + Mn2+ (aq) . Is this reaction spontaneous as written? 6. Draw the galvanic cell (include all labels) and calculate the standard cell potential for the cell described below: Zn ⎥ Zn2+ ⎥⎥ Cu2+ ⎥ Cu Calculate the cell potential if the concentration of the zinc solution was cut in half. 4 ...
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