Worksheet: The Henderson–Hasselbalch Equation

In this worksheet, we will practice using the Henderson–Hasselbalch equation, calculating pH from the pKa and concentrations of conjugate acid–base pairs.

Q1:

Consider the equilibrium shown. CHNH()+HO()CHNH()+OH()32233+–baqlaqaq,𝐾=4.4×10

What is [OH]– in a solution of 0.125 M  CHNH32 and 0.130 M  CHNHCl33 at 25∘C?

  • A 2 . 2 × 1 0   M
  • B 9 . 7 × 1 0   M
  • C 8 . 4 × 1 0   M
  • D 4 . 6 × 1 0   M
  • E 4 . 2 × 1 0   M

Q2:

Consider the equilibrium shown. HNO()+HO()HO()+NO()223+2–aaqlaqaq,𝐾=4.5×10

What is [HO]3+ in a solution of 0.065 M HNO2 and 0.040 M NaNO2?

  • A 4 . 5 × 1 0  
  • B 1 . 7 × 1 0  
  • C 1 . 1 × 1 0  
  • D 2 . 8 × 1 0  
  • E 7 . 3 × 1 0  

Q3:

What concentration of NHNO43 is required to make [OH]=–1.0×10 in a 0.200 M solution of NH3? 𝐾b of NH3 is 1.8×10.

Q4:

Consider the equilibrium shown. NH()+HO()NH()+OH()324+–baqlaqaq,𝐾=1.8×10

What is [OH]– in a solution of 1.35 M  NH3 and 0.82 M  NHNO43?

  • A 9 . 1 × 1 0    M
  • B 7 . 2 × 1 0    M
  • C 1 . 1 × 1 0   M
  • D 3 . 4 × 1 0    M
  • E 3 . 0 × 1 0   M

Q5:

What concentration of NaF is required to make [HO]3+=2.5×10 in a 0.320 M solution of HF? 𝐾a of hydrofluoric acid is 3.5×10.

Q6:

A 1.00 L aqueous buffer solution is prepared from 0.20 mol  NH3 and 0.40 mol  NHNO43. The 𝐾b of NH3 is 1.8×10 and the self-ionization constant of water, 𝐾w, is 1.0×10. Calculate, to 1 decimal place, the pH of the buffer solution.

Q7:

To 2 significant figures, what mass of NHCl4 must be added to 0.650 L of a 0.120 M solution of NH3 to give a buffer solution with a pH of 9.08? Assume a negligible change in volume as the solid is added. The 𝐾b of NH3 is 1.8×10.

Q8:

A buffer solution is prepared from equal volumes of 0.200 M acetic acid and 0.600 M sodium acetate. The 𝐾a of acetic acid is 1.80×10.

Is the solution acidic, neutral, or basic?

  • AAcidic
  • BNeutral
  • CBasic

Q9:

Saccharin, CHNSOH743, is a weak acid (𝐾=2.10×10a). If a 0.250 L solution with a buffered pH of 5.48 is prepared from 2.00×10 g of sodium saccharide, Na(CHNSO)743, what is the equilibrium concentration of saccharin in the solution?

  • A 1 . 0 2 × 1 0   M
  • B 6 . 1 5 × 1 0   M
  • C 5 . 6 9 × 1 0   M
  • D 3 . 9 0 × 1 0   M
  • E 8 . 1 6 × 1 0   M

Q10:

A 0.500 L aqueous buffer solution is prepared from 0.165molHPO34 and 0.230molKHPO24. The 𝐾a of HPO34 is 7.5×10 and the self-ionization constant of water, 𝐾w, is 1.0×10. Assuming that HPO34 behaves as a monoprotic acid, calculate, to 1 decimal place, the pH of the buffer solution.

Q11:

Consider the shown equilibrium. CHCOH()+HO()HO()+CHCO()3223+32–aaqlaqaq,𝐾=1.8×10

What is [HO]3+ in a solution of 0.25 M  CHCOH32 and 0.030 M   CHCONa32?

  • A 1 . 8 × 1 0   M
  • B 6 . 2 × 1 0   M
  • C 8 . 1 × 1 0   M
  • D 1 . 5 × 1 0   M
  • E 2 . 2 × 1 0   M

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