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General Chemistry 120; Spring 2022Exam 6Acid equilibrium constantsKa for HF = 7.2x10-4Ka for acetic acid CH3COOH = 1.80x10-5Ka for HCN = 4.0x10-10Ka for NH4+ = 5.55x10-10Ka for formic acid HCOOH = 1.78x10-4Solubility productsKsp for BaSO4(s) = 1.1x10-10Ksp for PbCl2(s) = 1.7x10-5Ksp for PbSO4(s) = 2.5x10-8Ksp for Ag2CrO4(s) = 9.0x10-12Ksp for AgCN(s) = 6.0x10-17Ksp for MnCO3 = 2.3x10-11Ksp for Mg(OH)2 = 5.6x10-12Ksp for AgBr = 5.4x10-13Ksp for AgCl = 1.6x10-10Ksp for Sr(SO4) = 3.8x10-7Thermodynamic QuantitiesSubstanceC (graphite) 0 5.6Ca(s) 0 41.59Ca(OH)2-986.09 83.CH3OH (l) -238.4 127.2C6H12O6 -1275 212CO2(g) -394 214CO (g) -110.5 197.7CS2 (g) 116.7 237.8H2(g) 0 130.7H2O (g) -242 189H2S(g) -20.6 205.8H2SO4(l) -814 156.9NO(g) 90 211NO2(g) 34 240O2(g) 0 205.1O3(g) 143 239S (s) 0 32.1SO2 (g)-296.8 248.2SO3 (g)-395.8 256.8Energy ConstantR = 8.314 J/molKQuestion 1P T/F The entropy change for a spontaneous chemical reaction cannot be negative. Question 2P T/F. Viewed informally, work is “concentrated” energy while heat is “dissipated” energy.Question 3P T/F According to the third law of thermodynamics, there is no entropy at zero degrees Kelvin. Question 4P T/F. Work energy from a reaction that is exergonic can be harnessed and used. Question 5P T/F. The concentration of a salt that can dissolve at equilibrium is called its solubility.Question 6P T/F The solubility of Mg3(PO4)2 could be increased by adding a small amount of base. Question 7P Which of the following statements are correct?I If G0rxn is negative and G is positive for particular conditions, the reaction will occur spontaneously under those conditions.II The First Law of Thermodynamics states that “energy cannot be converted from one form to another”.III The heat generated by a system can only be used to do work if there is a temperature gradient. A. All statements are correctB. Only statements I and II are correctC. Only statements II and III are correctD. Only statement III is correctE. None of the statements is correctQuestion 8P Ag2CrO4 (Mol wt = 332 gm/mol) dissolves to form silver ions (Ag+) and chromateions (CrO42-) in solution. A student added 0.223 grams of Ag2CrO4 to water such that the final volume was 775 mL. What will be the concentration of silver ions at equilibrium (in M)?A. 1.31x10-4B. 2.62x10-4C. 8.67x10-4D. 6.72x10-4E 1.31x10-5Question 9P Referring to the previous problem, how many grams of Ag2CrO4 will remain undissolved at equilibrium? A. 0.223B. 0.222C. 0.189D. 0.096E. 0.001Question 10P G0 = -67 kJ/mol for the reaction {2H2S(g) + SO2(g) ⇄ 3S(s) + 2H2O(g)} at 25 C.Find G (in kJ/mol) for the same reaction when PH2S = 110-3 bar; PSO2 = 110-2 bar, PH2O(g) = 310-4 bar, and 2.31 grams of solid sulfur are at equilibrium at 25 C. A. 0B. -72.4C. -54D. -5380E. -61.5Question 11P What is G0 (in KJ/mol) at 25 C for the reaction A. -5.55x109B. +2.41x104 C. -4460D. +55590E. -55.6Question 12P. You and your friend (who didn’t take Chem 120) are each given a 55 liter drum of20.0 µM AgCl. Your friend pours off the liquid, and collects the solid AgCl at the bottom. Youfirst add 1 Kg of NaCl, mix it, and let it reach equilibrium before pouring off the liquid and collecting the solid AgCl. How many more grams of AgCl did you collect? A 1.24 gB 0.94 gC 0.24 gD 0.10 gE 0.01


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TAMU CHEM 120 - Exam 6

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