Worksheet: Dissociation Constants and pH

In this worksheet, we will practice converting between the pH or pOH of a solution and the dissociation constants of dissolved acids and bases.

Q1:

Aniline is an amine that is used to manufacture dyes. It is isolated as, aniline, hydrochloride, [CHNH]Cl653+–, a salt prepared by the reaction of the weak base aniline and hydrochloric acid. What is the pH of a 0.233 M solution of aniline hydrochloride, to 3 significant figures? 𝐾b of aniline is 4.3×10.CHNH()+HO()HO()+CHNH()653+23+652aqlaqaq

  • A3.01
  • B1.99
  • C2.63
  • D2.14
  • E5.76

Q2:

Formic acid, HCOH2, is the irritant that triggers the body’s reaction to ant stings.

What is the concentration of hydronium ions in a 0.534 M solution of formic acid? HCOH()+HO()HO()+HCO()223+2–aqlaqaq Take 𝐾=1.8×10a.

  • A9.6×10 M
  • B1.8×10 M
  • C5.0×10 M
  • D9.8×10 M
  • E6.0×10 M

Q3:

What is the pH of a 0.25 M solution of trimethylamine, a weak base? (CH)N()+HO()(CH)NH()+OH()33233+–aqlaqaq Take 𝐾=6.3×10b.

Q4:

What is the concentration of hydroxide ions in a 0.0325 M solution of ammonia, a weak base with a 𝐾b of 1.76×10?

  • A7.56×10 M
  • B6.10×10 M
  • C9.34×10 M
  • D6.62×10 M
  • E1.12×10 M

Q5:

The pH of a 0.0516 M solution of nitrous acid (HNO2) is 2.34. Calculate the 𝐾a of nitrous acid to 2 significant figures. HNO()+HO()HO()+NO()223+2–aqlaqaq

  • A4.7×10
  • B4.0×10
  • C4.4×10
  • D2.1×10
  • E4.6×10

Q6:

The pH of a solution of household ammonia, a 0.950 M solution of NH3 is 11.612. What is 𝐾b for NH3 to 2 significant figures?

  • A5.6×10
  • B1.7×10
  • C1.8×10
  • D4.3×10

Q7:

Sodium bisulfate (NaHSO4) is used in some househould cleaners because it contains the HSO4– ion, which is weakly acidic. HSO()+HO()HO()+SO()4–23+42–aqlaqaq The 𝐾a of HSO4– is 1.2×10. Calculate, to 2 decimal places, the pH of a HSO4– solution with a concentration of 0.50 M.

Q8:

Caffeine, a weak base, has a 𝐾b value of 2.5×10. Calculate, to 1 decimal place, the pH of a 0.010 M aqueous caffeine solution. CHNO()+HO()CHNOH()+OH()81042281042+–aqlaqaq

Q9:

The 𝐾a of HCN is 4.9×10. Calculate, to 1 decimal place, the pH of a 0.083 M solution of CN–.

Q10:

Aluminum chloride dissolves completely to produce the hydrated aluminum ion [Al(HO)]263+, which behaves as a monoprotic acid. The 𝐾a of [Al(HO)]263+ is 1.4×10. Calculate, to 2 decimal places, the pH of a 0.10 M solution of aluminum chloride.

Q11:

The pH of a 0.15 M solution of HSO4– is 1.43. What is 𝐾a for HSO4– from these data?

  • A2.3×10
  • B8.9×10
  • C3.6×10
  • D1.2×10
  • E1.6×10

Q12:

The pH of a solution of household ammonia, a 0.950 M solution of NH3, is 11.612. What is 𝐾b for NH3 from these data?

  • A5.05×10
  • B9.58×10
  • C3.16×10
  • D3.58×10
  • E1.77×10

Q13:

White vinegar is a 5.00% by mass solution of acetic acid in water. If the density of white vinegar is 1.007 g/mL, what is the pH at 25∘C? The 𝐾a of acetic acid is 1.8×10.

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