Target: 10 Questions in 10 minutes

An IB Chemistry data booklet is helpful
1. The pOH of a 20 g dm-3 potassium hydroxide is:
  • A.   -1.30
  • B.   0.356
  • C.   0.448
  • D.   13.6
2. What is the concentration of OH- in 0.5 mol dm-3 of NH3?
The pKb of NH3 = 4.75 and assume there is negligible ionization of NH3 in water.
  • A.   0.00298
  • B.   0.00422
  • C.   0.500
  • D.   0.707

3. The ion product constant of water at 50°C is 5.43 x 10-14 mol2 dm-6.
Which of the following statements is correct about an aqueous solution of [H+] = 1x10-7 mol dm-3 at this temperature?

I. pH = 7
II. pOH = 6.27
III. The solution is neutral
  • A.   I and II only
  • B.   I and III only
  • C.   II and III only
  • D.   I, II and III
4. What is the pH of 0.5 mol dm-3 benzoic acid, which has a pKa = 4.20?
  • A.   0.301
  • B.   2.10
  • C.   2.25
  • D.   4.20
5. The ion product constant of water at 70°C is 1.59 x 10-13 mol2 dm-6. What is the pH of 0.25 mol dm-3 of barium hydroxide at this temperature?
  • A.   0.60
  • B.   12.2
  • C.   12.5
  • D.   12.8
6.What is the pOH of a solution of 0.075 mol dm-3 ethylamine CH3CH2NH2, which has a pKb = 3.35?
  • A.  1.12
  • B.   2.24
  • C.   3.36
  • D.   11.8
7. Which of the following amines has the strongest conjugate acid?
  • A.  Methylamine, pKb = 3.34
  • B.  Diethylamine, Kb =  0.000537
  • C.  Triethylamine, pKb = 3.25
  • D.  Phenylamine, Kb = 7.41x10-10
8. Which of the following statements about Ka of an acid is true?
  • A.   A weak acid always has a pKa of less than 7 at 25°C.
  • B.   Ka increases with increasing concentrations of acids.
  • C.   Ka is independent of the temperature of the acids.
  • D.   A stronger acid has a lower pKa value than a weaker acid.

9. Which of the following statements about the Ka and Kb of a conjugate acid-base pair is/are true?

I. Ka / Kb = Kw
II. Ka + Kb = Kw
III. pKa + pKb = pKw
  • A.   I only
  • B.   II only
  • C.   III only
  • D.   II and III only
10. The pKa of propanoic acid is 4.87 and that of chloroethanoic acid is 2.87. What is the approximate ratio of [H+] in propanoic acid to chloroethanoic acid if both acids have the concentration of 0.100 mol dm-3 ?
  • A.  0.010
  • B.   0.10
  • C.   1.7
  • D.   100