Acid base

Acid base

- 1 - Acid-Base Titrations 1. How many millilitres of 0.100 M HCl are required to neutralize 25.0 mL of 0.100 M Ba(OH)2? 2. What is the molarity of a hydrochloric acid solution, 30.0 mL of which is just neutralized by 48.0 mL of 0.100 M NaOH? 3. Exactly 50.0 mL of HOCl solution of unknown concentration was titrated with 0.100 mol NaOH. An end point was reached when 38.5 mL of the base was added. Calculate the molar concentration of the HOCl solution. 4. What can make the titrated solution at the equivalence point in an acid-base titration have a pH not equal to 7.00. How does this possibility affect the choice of an indicator? 5. What is a good indicator for titrating potassium hydroxide with hydrobromic acid? Explain. 6. In the titration of an acid with a base, what condition concerning the quantities of reactants ought to be true at the equivalence point? 7. When 50 mL of 0.10 M formic acid is titrated with 0.10 M sodium hydroxide, what is the pH at the equivalence point? (Be sure to take into account the change in volume during the titration.) What is a good indicator for this titration? 8. Calculate the pH of the resulting solution after 20.00 mL of 0.20 M NaOH has been added to 25.00 mL of 0.20 M HC2H3O2. 9. To obtain the data needed to plot a titration curve for the titration of a strong acid with a strong base, a chemist used 25.00 mL of 0.1000 M HCl. The molarity of the base was also 0.1000 M, and this solution was added in small portions to the acid. Calculate the pH of the resulting solution after each of the following quantities of base had been added to the original solution (you must take into account the change in volume). Graph the result. (a) 0 mL (d) 24.99 mL (g) 25.10 mL (b) 10.00 mL (e) 25.00 mL (h) 26.00 mL (c) 24.90 mL (f) 25.01 mL (i) 50.00 mL 10. For each of the following titration, specify the indicator from column II that should - 2 - be used. State your reasons, but do not make any quantitative calculations. Column I Column II a) NaOH + KHC8H4O4 neutral red (6.8-8.0) b) NaOH + HCl bromocresol green(3.8-5.4) c) NaHCO3 + HCl 0-cresolphthalein(8.2-9.8) 11. ΔHo for the reaction H+(aq) + OH−(aq) Æ H2O is - 56.8kJ. Given that the ionic product of water, KW, is 0.61x10−1 at 291K, calculate KW and hence determine neutral pH at 310K. (Ans: 6.79) 12. Calculate the pH of the following solutions: (a) 0.05M HCl (b) 0.1M acetic acid (Ka = 1.75 x 10−5 (M)) (c) 0.1M aniline (Kb = 3.82 x 10−10 (M)) (d) 0.1M acetic acid plus 0.001 M HCl (e) 0.16M acetic acid plus 0.044 M sodium acetate (Ans: 1.3, 2.88, 8.79, 2.27, 4.2) Polyatomic Acids & Bases 13. Phosphorus acid, H3PO4, is actually a diprotic acid; Ka1 = 1.0 X 10-2 and Ka2 = 2.6 X 10-7. What are the values of [H+], pH and HPO32- in a 1.0 M solution? 14. Tellurium, in the same family as sulphur, forms an acid analogous to sulphuric acid and called telluric acid. It exists, however, as H6TeO6 (which looks like H2TeO4 + 2 H2O). It is a diprotic acid. Ka1 = 2.1 X 10-8 and Ka2 = 6.5 X 10-12. Calculate [H+], pH, and [H4TeO62-] in a 0.25 M solution of H6TeO6. 15 How many millilitres of 0.05 M phosphoric acid will be required for reaction with 50 mL of 0.50 M KOH to yield a) KH2PO4, b) K2HPO4, c) K3PO4? 16 Write formulas for the primary, secondary, and tertiary lithium salts of H3PO4. Write equations for the equilibria present in an aqueous solution of a) H2SO4, b) H3PO4. . 1.3, 2.88, 8.79, 2.27, 4.2) Polyatomic Acids & Bases 13. Phosphorus acid, H3PO4, is actually a diprotic acid; Ka1 = 1.0 X 10-2 and Ka2 = 2.6 X. forms an acid analogous to sulphuric acid and called telluric acid. It exists, however, as H6TeO6 (which looks like H2TeO4 + 2 H2O). It is a diprotic acid.