Buffers

Overshot pH rescuer: practice problems

Work out the result for overshot pH rescuer. Every answer here is computed by the same tested calculator the rest of the site uses, so a solution can never drift away from the maths.

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Problem 1 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 7.5
  • Target pH: 6.9
  • Buffer concentration (M): 0.04
  • Volume (mL): 2500
  • Titrant concentration (M): 1.5
Show the answer and the working

Add 10.08 mL of strong acid (1.5 M).

  1. Base now / target: n·r/(1+r) = 21.595 / 6.471 mmol
  2. Add: strong acid = 10.083 mL

Open this in the calculator to change the numbers.

Problem 2 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 8.0
  • Target pH: 6.9
  • Buffer concentration (M): 0.05
  • Volume (mL): 1000
  • Titrant concentration (M): 1
Show the answer and the working

Add 20.04 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 23.276 / 3.235 mmol
  2. Add: strong acid = 20.04 mL

Open this in the calculator to change the numbers.

Problem 3 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 8.5
  • Target pH: 7.4
  • Buffer concentration (M): 0.05
  • Volume (mL): 2000
  • Titrant concentration (M): 1
Show the answer and the working

Add 55.41 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 73.363 / 17.95 mmol
  2. Add: strong acid = 55.413 mL

Open this in the calculator to change the numbers.

Problem 4 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 7.5
  • Target pH: 7.4
  • Buffer concentration (M): 0.05
  • Volume (mL): 7500
  • Titrant concentration (M): 1
Show the answer and the working

Add 13.67 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 80.98 / 67.314 mmol
  2. Add: strong acid = 13.666 mL

Open this in the calculator to change the numbers.

Problem 5 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 9
  • Target pH: 8.4
  • Buffer concentration (M): 0.05
  • Volume (mL): 7500
  • Titrant concentration (M): 0.5
Show the answer and the working

Add 158.03 mL of strong acid (0.5 M).

  1. Base now / target: n·r/(1+r) = 336.379 / 257.363 mmol
  2. Add: strong acid = 158.032 mL

Open this in the calculator to change the numbers.

Problem 6 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 9
  • Target pH: 7.9
  • Buffer concentration (M): 0.03
  • Volume (mL): 1000
  • Titrant concentration (M): 2
Show the answer and the working

Add 7.32 mL of strong acid (2 M).

  1. Base now / target: n·r/(1+r) = 26.91 / 12.268 mmol
  2. Add: strong acid = 7.321 mL

Open this in the calculator to change the numbers.

Problem 7 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 8.0
  • Target pH: 7.9
  • Buffer concentration (M): 0.01
  • Volume (mL): 1500
  • Titrant concentration (M): 3
Show the answer and the working

Add 0.28 mL of strong acid (3 M).

  1. Base now / target: n·r/(1+r) = 6.983 / 6.134 mmol
  2. Add: strong acid = 0.283 mL

Open this in the calculator to change the numbers.

Problem 8 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 9
  • Target pH: 7.4
  • Buffer concentration (M): 0.04
  • Volume (mL): 5000
  • Titrant concentration (M): 1
Show the answer and the working

Add 143.5 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 179.402 / 35.901 mmol
  2. Add: strong acid = 143.501 mL

Open this in the calculator to change the numbers.

Problem 9 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 9
  • Target pH: 7.4
  • Buffer concentration (M): 0.075
  • Volume (mL): 4000
  • Titrant concentration (M): 1
Show the answer and the working

Add 215.25 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 269.103 / 53.851 mmol
  2. Add: strong acid = 215.251 mL

Open this in the calculator to change the numbers.

Problem 10 Overshot pH rescuer

Work out the result for overshot pH rescuer.

  • Buffer: Tris (pKa 8.06)
  • Current pH: 8.5
  • Target pH: 7.4
  • Buffer concentration (M): 0.075
  • Volume (mL): 4000
  • Titrant concentration (M): 1
Show the answer and the working

Add 166.24 mL of strong acid (1 M).

  1. Base now / target: n·r/(1+r) = 220.09 / 53.851 mmol
  2. Add: strong acid = 166.239 mL

Open this in the calculator to change the numbers.

More buffers practice

Same topic, different calculation

Buffer / pH

Henderson-Hasselbalch, the acid/base split for a target pH.

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