Competitive Exams: Chemistry MCQs (Practice-Test 7 of 31)

  1. Calculate the molar hydronium ion concentration, [H3O + ], in a 2.0 × 10 − 3 M solution of hypoiodious acid (HOI, Ka = 2.3 × 10 − 11).

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  2. Calculate the hydroxide ion concentration, [OH-], in a 0.10 M solution of sodium formate (For the formate ion, OF-, Kb = 5.6 × 10 − 11.).

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  3. The dissociation constant for nitrous acid, HNO2, is Ka = 5.1 × 10 − 4. What is the dissociation constant, Kb, for nitrite ion, NO2-, the conjugate base of nitrous acid?

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  4. Which of the following solutions would be best to buffer a solution near pH = 4 ([H3O + ] = 1.0 × 10 − 4).

    1. 1.0 × 10 − 4 M HCl

    2. 1.0 × 10 − 4 M NaOH

    3. A solution containing approximately equal concentrations of formic acid (Ka = 1.8 × 10 − 4) and sodium formate.

    4. A solution containing approximately equal concentrations of hypochlorous acid (HOCl, Ka = 2.9 × 10 − 8) and sodium hypochlorite (NaOCl).

    5. A solution containing approximately equal concentrations of ammonia (Kb = 1.8 × 10 − 5) and ammonium chloride.

  5. A 25.00 mL aliquot of a vinegar sample is diluted to 250.00 mL with water. Then a 25.00 mL aliquot of the diluted sample is titrated with strong base, requiring 22.13 mL of 0.1027 M sodium hydroxide to reach the endpoint. What is the molar concentration of acid in the original vinegar sample before dilution?

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  6. Assume that a 25.00-mL aliquot of a solution containing a monoprotic weak acid is titrated with a standard solution of sodium hydroxide, requiring 22.42 mL of titrant to reach the end point. At which milliliter volume listed below will the pH be equal to the pKa of the weak acid?

    1. N/A

    2. N/A

    3. N/A

    4. N/A

  7. Which of the following solutions would be an acid/base buffer?

    1. 0.1 M HCl, a strong acid

    2. 0.1 M acetic acid, a weak acid

    3. 0.1 M sodium acetate

    4. 0.1 M acetic acid plus 0.1 M sodium acetate

    5. pure water

  8. Which of the following solutions would be the most basic?

    1. 0.1 M HCl, a strong acid

    2. 0.1 M acetic acid, a weak acid

    3. 0.1 M sodium acetate

    4. 0.1 M acetic acid plus 0.1 M sodium acetate

    5. pure water

  9. Calculate the hydronium ion concentration, [H3O + ], in a 0.15 M solution of sodium formate. For formic acid, Ka = 1.8 × 10 − 4.

  10. In which of the following situations would the weak acid dissociate to the largest extent (i.e.. have the largest percent dissociation)?

    1. 0.01 M formic acid, Ka = 1.8 × 10 − 4

    2. 0.1 M formic acid, Ka = 1.8 × 10 − 4

    3. 0.1 M acetic acid, Ka = 1.8 × 10 − 5

    4. 0.01 M formic acid (Ka = 1.8 × 10 − 4) plus 0.15 M sodium formate

    5. 1.0 × 10 − 4 M phenol, a monoprotic weak acid with Ka = 1.0 × 10 − 10

  11. In which of the following solutions would the dissociation of water make the largest contribution to the total hydronium ion concentration?

    1. 0.01 M formic acid, Ka = 1.8 × 10 − 4

    2. 0.1 M formic acid, Ka = 1.8 × 10 − 4

    3. 0.1 M acetic acid, Ka = 1.8 × 10 − 5

    4. 0.01 M formic acid (Ka = 1.8 × 10 − 4) plus 0.15 M sodium formate

    5. 1.0 × 10 − 4 M phenol, a monoprotic weak acid with Ka = 1.0 × 10 − 10

  12. A 25.0-mL aliquot of a monoprotic acid solution is diluted to 100 mL. Then a 25.0-mL aliquot of this solution is titrated with a standard sodium hydroxide solution, requiring 17.1 mL of 0.107 M sodium hydroxide to reach the end point. What is the molar concentration of the acid in the original solution?