MCAT General Chemistry Freestanding Practice Questions: Acids and Bases

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1. The pH of a CH3COOH solution is < 7 because when this compound is added to water:

  • A. CH3COOH donates H+, making [H+] > [OH-].
  • B. CH3COOH loses OH-, making [H+] < [OH-].
  • C. CH3COO- deprotonates H2O, increasing [OH-].
  • D. CH3COOH dissociation increases [H+], thereby increasing Kw.

2. All of the following are amphoteric EXCEPT:

  • A. HCO3-
  • B. H2PO4-
  • C. SO42-
  • D. HOOCCOO-

3. A graph depicting a titration of a weak acid with a strong base will start at a:

  • A. high pH and slope downwards with an equivalence pH equal to 7.
  • B. high pH and slope downwards with an equivalence pH below 7.
  • C. low pH and slope upwards with an equivalence pH equal to 7.
  • D. low pH and slope upwards with an equivalence pH above 7.

4. List the following compounds by increasing pKa:

I. H2SO4

II. NH3

III. CH3CH2COOH

IV. HF

  • A. I < III < II < IV
  • B. I < IV < III < II
  • C. III < I < IV < II
  • D. II < III < IV < I

5. The amino and carboxyl terminals of alanine lose protons according to the following equilibrium:

Which of the following indicators would be best used to determine the second equivalence point when alanine is titrated with sodium hydroxide?

  • A. Methyl violet (pKb = 13.0)
  • B. Methyl yellow (pKb = 10.5)
  • C. Thymol blue (pKb = 12.0)
  • D. Phenolphthalein (pKb = 4.9)

6. The Ka of HSCN is equal to 1 × 10-4. The pH of a HSCN solution:

  • A. will be approximately 4.
  • B. will be approximately 10.
  • C. will increase as [HSCN] increases.
  • D. cannot be determined from the information given.

7. A 25.0 mL solution of 0.2 M acetic acid (pKa = 4.76) is mixed with 50 mL of 1.0 M sodium acetate (pKb = 9.24). What is the final pH?

  • A. 4.8
  • B. 5.8
  • C. 9.2
  • D. 10.2