CH302 Practice Quiz 5 on Complex Equilibria 1. Na2SO3 is the basic salt of sulfurous acid which is a weak diprotic acid. If Ka1 = 1.5 x 10-2 and Ka2 = 1.2 x 10-7, what is the [H3O+] concentration in a sulfite (SO3=) solution that is 0.025M? 1. 9.6 M correct 2. 4.4 M 3. 10.1 M 4. 9.0 M 2. What is the pH of a 0.5M solution of an acid with Ka = 1.2 x 10-1? 1. 0.71 correct 2. 3.05 3. 6.8 4. 11.08 3. What is the pH of 0:15 M Na2HPO4(aq) if Ka1 = 7.6 x 10-3, Ka2 = 6.2 x 10-8 and Ka3 = 2.1 x 10-13? 1. 9.93 correct 2. 8:31 3. 7.82 4. 6.92 5. 3.02 . 4. Write the charge balance equation for a dilute aqueous solution of HClO2. 1. [ClO2-] = [OH-] + [H3O+] 2. [H3O+] = [OH-] 3. [H3O+] = [ClO2-] 4. [H3O+] = [ClO2-] + [OH-] correct 5. [HClO2]initial = [ClO2-] 5. [HClO2]initial = [HClO2] + [ClO2-] 5 For a solution labeled 0.10 M Na2S(aq)," 1. [S=] > 0.10 M. 2. [S= ] > [HS-] correct 3. [S= ] = [HS-] 4. [OH-] = 0.10 M. 5. [OH-] > 0.10 M. 6 A weakly basic solution with a pH near 7 is formed when a solution of 1 x 10-7 moles of NH3 is added to 1 liter of water. How many equations must be solved in order to accurately calculate all the unknown concentrations formed at equilibrium in solution? 1. 1 2. 2 3. 3 4. 4 correct 5. 5 6. 6 7. 77. What is the concentration of HSO4- in 0.1 M H2SO4? Ka1 is strong and Ka2 = 1:2 a 10-2. 1. 9.8 x 10-3 M correct 2. 1:2 x 10-3 M 3. 4:0 x 10-2 M 4. 1:0 x 10-3 M 5. 4:0 x 10-2 M 8. There are three sources of protons to be considered in calculating the pH of a solution formed when equal volumes of 1 x 10-9 M HCl and 1 x 10-9 M acetic acid (HAc) are added to water. Assume a Ka of 1:8 x 10-5 for acetic acid. Rank from most to least, the concentration of protons contributed at equilibrium from HCl, HAc and H2O. 1. HCl, HAc, H2O 2. HAc, HCl, H2O 3. HAc, H2O, HCl 4. H2O, HCl, HAc correct 5. HCl, H2O,
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