Chem100A_Exp2_HomoChemEq_Quiz_20110406_KEY -...

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Spring 2011 Student ID:_______________________________ Experiment 2: Homogeneous Chemical Equilibrium Quiz #1 (20 points)–April 06, 2011 1. (4 points)Write the expression for the equilibrium constant, K c , for the esterification reaction: What does the numerical magnitude of equilibrium constant, K c , indicate? What do LARGE values of K c indicate? The numerical magnitude of K c is a direct indication of the extent of completion of a chemical reaction at equilibrium. Large values of K c indicate HIGH PRODUCT and LOW REACTANT equilibrium concentrations. 2. (4 points) True or False: a. K c depends on the initial concentration of reactants and products.__ T ___ b. K c depends on the temperature.__ T ___ c. K c depends on the conceration of catalyst.__ F ___ d. Kc depends on the pressure.__ T ___ 3. (4 points) What volume of 50% NaOH (40g/mol) solution is needed to prepare 300mL of a 1.5M NaOH solution? (For the specific gravity of NaOH, use 1.522).
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Unformatted text preview: ( 1.522g/mL)(0.5)(1mol/40g NaOH)(1000mL/L) = 19M NaOH (19M NaOH)(x mL) = (1.5M NaOH)(300mL) x = (300*1.5)/19 = 23.6mL 24mL 4. (4 points) Calculate the concentration of NaOH when 3.0684g KHP (204g/mol) is weighed out and standardized with ~1.5M NaOH. The amount of NaOH used to titrate the mixture was 10.30mL. (3.0684g KHP)(1mol/204g KHP) = 0.015mol KHP 0.015mol NaOH (0.015mol NaOH)/(0.01030L NaOH) = 1.460M NaOH 5. (4 points) What is an equivalence point? How will we determine when the titration has reached its equivalence point? Equivalence point is a point in a titration when the amount of added standard reagent exactly equals the amount of analyte. To determine when the titration has reached its equivalence point an indicator is added to the analyte solution to give an observable physical change (the end point) at or near the equivalence point....
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