• For the following reaction of hypochlorous acid (HOCl) with water,
  HOCl + H₂O <==> H₃O⁺ + OCl^-

  what would be the effect of adding sodium hypochlorite (NaOCl) to the reaction at equilibrium?

  1. The concentrations of both HOCl and H₃O⁺ would increase.
  2. The concentrations of both HOCl and H₃O⁺ would decrease.
  3. The concentration of HOCl would increase and the concentration of H₃O⁺ would decrease.
  4. The concentration of HOCl would decrease and the concentration of H₃O⁺ would increase.
  5. There would be no change because sodium hypochlorite is a salt without any acidic or basic properties.

   

• Calculate the molar hydronium ion concentration in a solution containing 0.23 M hypochlorous acid (HOCl), a monoprotic weak acid used in bleach solutions. For HOCl, K_a = 2.9 x 10^-8.

   

• Given three separate solutions containing equal concentrations of formic acid (K_a = 1.7 x 10^-4), phenol (K_a = 1.3 x 10^-10), and acetic acid (K_a = 1.8 x 10^-5), select the response below that has the acids arranged in order of increasing percent dissociation at equilibrium.

   

  1. formic < phenol < acetic
  2. formic < acetic < phenol
  3. acetic < formic < phenol
  4. phenol < acetic < formic
  5. No response is correct.

   

• From the following choices, select the one that would be the most basic (least acidic).
  1. 0.1 M hydrochloric acid (a strong acid)
  2. 0.1 M acetic acid (a weak acid)
  3. 0.1 M sodium acetate (the salt of a weak acid)
  4. 0.1 M ammonium chloride (the salt of a weak base)
  5. pure water

   

• The reactions of perchloric acid (HClO₄) and acetic acid (HOAc) in water can be written as:

  HClO4  +  H2O  -->   H3O+  +  ClO4-     and
  
  HOAc  +  H2O   <=>    H3O+  +  OAc-
  

  From these reactions it can be concluded that:

  1. acetic acid is a stronger acid than perchloric acid.
  2. acetate ion is a weaker base than perchlorate ion.
  3. acetate ion is a stronger base than perchlorate ion.
  4. water is a very strong acid.
  5. none of the above is correct.

   

• If 10 mL a 1.0 x 10^-4 M solution of a strong acid were added to 100 mL each of one solution containing 1.8 x 10^-5 M hydrochloric acid and a second solution containing 1.0 M acetic acid (K_a = 1.8 x 10^-5) plus 1.0 M sodium acetate, it is expected that the:
  1. pH of both solutions would remain unchanged.
  2. change in pH would be very large in both solutions.
  3. change in pH would be the same in both solutions.
  4. change in pH would be larger in the solution containing acetic acid and sodium acetate.
  5. change in pH would be larger in the HCl solution.

   

• Addition of a strong acid to a solution of acetic acid at equilibrium (HOAc + H₂O <=> H₃O⁺ + OAc^-) would cause the:
  1. acetate ion concentration to decrease.
  2. acetate ion concentration to increase.
  3. pH to increase.
  4. hydroxide ion concentration to increase.
  5. None of the above is correct.

   

• Calculate to a first approximation the molar concentration of hydronium ion in a 0.171 M solution of benzoic acid (HOBz, a monoprotic weak acid with K_a = 6.5 x 10^-5).

   

• Given that the acid dissociation constant for benzoic acid (HOBz) is K_a = 6.5 x 10^-5, calculate the basic dissociation constant, K_b , of the benzoate ion (OBz^-).

   

• Consider the following data for the series of hydrogen halide Bronsted acids,

  Acid                     Ka
  
   HF                   7.2 x 10-4
   HCl                  1 x 106
   HBr                  1 x 109
   HI                   3 x 109
  

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