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Additional Aspects of Aqueous Equilibria

Additional Aspects of Aqueous Equilibria. Buffer Solutions. solution that resists changes in pH upon addition of small amounts of strong acid or base consists of a mixture of a weak acid and its conjugate base

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Additional Aspects of Aqueous Equilibria

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  1. Additional Aspects of Aqueous Equilibria

  2. Buffer Solutions • solution that resists changes in pH upon addition of small amounts of strong acid or base • consists of a mixture of a weak acid and its conjugate base • it works b/c the weak acid can neutralize small amounts of strong base and the weak base can neutralize small amounts of strong acid

  3. Common Ion Effect • decreases the ionization of a weak electrolyte when a common ion is added to the solution • Consider this: CH3COOH + H2O CH3COO- + H3O+ • adding NaCH3COO to the solution will increase [CH3COO-], causing the rxn to shift left, thus decreasing the ionization of acetic acid • resulting solution is a buffer containing a weak acid & a conjugate weak base

  4. To make a buffer solution, what weak acid must be added to an amount of sodium phosphate? Write a chemical reaction and its corresponding equilibrium expression.

  5. Understanding A/B reactions • SA + SB  NS + H2O • HCl + NaOH  H2O + NaCl • H+ + OH-  H2O • sol’n is neutral b/c both the acid and base ions are neutral ions • SA + WB  WA + NC • HCl + NaCH3COO  NaCl + CH3COOH • H+ + CH3COO-  CH3COOH • sol’n is slightly acidic • SB + WA  WB + NC • NaOH + CH3COOH  NaCH3COO + H2O • OH- + CH3COOH  CH3COO- + H2O • sol’n is slightly basic • WA + WB  does not measurably react

  6. Write and balance complete and net ionic equations for the reaction of ammonia solution with nitric acid.

  7. Calculating Buffer pH • calculated the same as the pH of a weak acid sol’n - RICE: • What is the pH of an aqueous mixture containing 0.20 M acetic acid and 0.10 M sodium acetate?

  8. Explain how nitric acid and sodium acetate can be used to make a buffer solution. Illustrate your answer using a chemical equation.

  9. What is the pH of a solution made by mixing 1.0 L of 0.10 M HCl with 2.0 L of 0.060 M NaOH

  10. What is the pH is a sol’n made by mixing 0.11 M HCl with 3.0 L of 0.080 M NaF?

  11. What is the pH of a sol’n made by mixing 2.5 L of 0.20 M CH3COOH with 1.0 L of 0.30 M KCH3COO?

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