What you are given
- Buffer: Tris (pKa 8.06)
- Current pH: 8.0
- Target pH: 7.4
- Buffer concentration (M): 0.05
- Volume (mL): 1000
- Titrant concentration (M): 1
Formula: Δn_base between current and target ratios; V = Δn / C_titrant
Buffers
How do you calculate overshot pH rescuer?
Overshot your buffer? Get the exact strong acid or base volume to fix it. The relationship used is Δn_base between current and target ratios; V = Δn / C_titrant.
Worked example
Every number below is computed by the calculator, not typed in
The working
- Base now / target:
n·r/(1+r)=23.276 / 8.975 mmol - Add:
strong acid=14.301 mL
Add 14.3 mL of strong acid (1 M).
Try it yourself
Two problems, with the working revealed
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): 0.015
- Volume (mL): 2000
- Titrant concentration (M): 3
Show the answer and the working
Add 1.51 mL of strong acid (3 M).
- Base now / target:
n·r/(1+r)=6.478 / 1.941 mmol - Add:
strong acid=1.512 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: 8.5
- Target pH: 8.4
- Buffer concentration (M): 0.01
- Volume (mL): 3000
- Titrant concentration (M): 1
Show the answer and the working
Add 1.42 mL of strong acid (1 M).
- Base now / target:
n·r/(1+r)=22.009 / 20.589 mmol - Add:
strong acid=1.42 mL
Open this in the calculator to change the numbers.
Do it with your own numbers.
The Overshot pH rescuer calculator is free, shows every step, flags the hazards, and works offline once loaded. No account, no signup.
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