A buffer holds pH where it is
- The idea
- Predict
- See it
- Why
- Check
The idea
“A buffer pushes the pH up, feeds the reaction, or keeps the temperature steady.”
A buffer comes labeled with a pH, so it's easy to picture it pushing the solution to that number. Its real job starts when acid or base shows up.
The short version
The mistake: A buffer pushes the pH up, feeds the reaction, or keeps the temperature steady.
What's actually true: A buffer resists changes in H+ concentration. It takes up or gives off H+, so the pH stays near where it started.
- A buffer is a weak acid mixed with its conjugate base, the same molecule minus one H+.
- Added H+ gets bound by the base form. Added OH- takes H+ from the acid form and becomes water. Free H+ barely changes.
- In an enzyme lab, a buffer keeps pH a controlled variable as the reaction runs. It doesn't feed the enzyme or touch the temperature.
On the exam: A buffer keeps pH steady by taking up or giving off H+ as acid or base is added.