Some Fundamental Constants and Conversion Factors 1 atm = XXXXXXXXXXPa 1 atm = 760 Torr 1 Torr = 1 mm Hg mu = XXXXXXXXXX * 10-27 Kg g = XXXXXXXXXXm/s2 (acceleration due to gravity) h = 6.626* 10-34 Js...

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Some Fundamental Constants and Conversion Factors 1 atm = 101325 Pa 1 atm = 760 Torr 1 Torr = 1 mm Hg mu = 1.660539 * 10-27 Kg g = 9.80665 m/s2 (acceleration due to gravity) h = 6.626* 10-34 Js (Plank's Constant) NA = 6.02208 * 1023 mole-1 (Avogadro's number) c = 2.99792 * 108 m/s (speed of light) (Rydberg's constant) me = 9.109*10-31 Kg (mass of an electron) eV = 1.602677·10-19 J e = 1.60217*10-19 C (charge on an electron) 1 J = kg·m2/s2 R = 8.31446 J/(mol K) = 0.0820574 L atm /(mol K) = 0.0831446 L bar/(mol K) (gas constant) Some useful Equations V = cC + dD, pH = -log([H+]) Ecell = Ecell0 - (RT ln Q)/nF if T =298.15 K then Ecell = Ecell0 - (0.025693V( ln Q)/n) ln K = nF Ecell0/RT if T = 298.15 K then ln K = n Ecell0/0.025693V G0 = -nF Ecell0 Acidity Constants Citric acid pKa1= 3.13 Citric acid pKa2= 4.76 Citric acid pKa3= 6.39 Sulfurous acid ()pKa1 = 1.81 Sulfurous acid ()pKa2 = 6.91 Hypochlorous acid (HClO/ClO-)pKa = 7.53 Chlorous acid (HClO2/ClO2- )pKa = 2.00 Normal Boiling Points H2- 252.9C Br2 58.8C HBr- 66.0C Please Read! Please use the constants provided or from your textbook. The key was built using these values. For the purposes of this exam consider Enthalpy and entropy values constant over temperature changes. 1. Given the following equilibria, write the equation defining the equilibrium coefficient for each. In “b” Identify the Acid, base, conjugate acid and conjugate base. There is also a change noted. Does that change shift the equilibrium to the products, reactants, or neither? Explain your answer for credit. Change: 20 mL of 0.25 mol HCl/L is added to the container. Change: 0.500 g of NaCH3COO is added Change: This reaction is in a rigid container and the temperature is increased from 25C to 100C. 2.A buffer using citrate species is compatible with the experiment we are performing. It needs to be at a pH of 4.25 and we are making 2.500 L of the buffer. It also must have the maximum buffering capacity, so no DI Water will be added to the solution to bring the volume to 2.500 L. The following solutions are in your stockroom to use. Citric Acid: 0.5000 mol /L Sodium Hydrogen Citrate: 0.5000 mol /L Sodium Dihydrogen Citrate: 0.7500 mol /L Sodium Citrate: 0.7500 mol /L A.Using the information provided by this document determine which buffer pair needs to be used Your choices are , or . Explain the reason behind your choice. Calculations can be accepted as part of the explanation. B.Once the buffer pair is selected, write the chemical equilibrium used in the buffer. C. 2.00 mL of 2.0 mol HCl/L acid is added to the buffer solution. Explain how that affects the equilibrium in the solution. Be specific. D.Calculate the ratio of conjugate base to acid. E.Determine the volume of each solution needed. Work space for Question 2 3.The Above diagram represents the fraction of each ionic species deriving from Citric Acid, H3C6H5O7 in an aqueous solution. a.Label points A, B, C and D with the appropriate citric acid or citrate ion species b.What is the pH at each of the points X, Y and Z? 4.The following are added to a 1.25 L Volumetric flask: · 15.36 g sodium chloride, NaCl ( = 57.52 g/mol) · 0.01598 g sodium hypochlorite pentahydrate, NaClO·5H2O ( = 164.515 g/mol) And the flask is filled to the line with DI water. Assume this is done at 25C. The salts are soluble and dissociate. A. Calculate the molar concentrations of ALL Chemical species in the solution. B. What is the pH of the resulting solution?