Simulation · Chemistry · Class 11
A buffer holds its pH
From the lesson Buffer solutions in Equilibrium. Change the values and watch what happens.
A buffer holds its pHChemistry · Class 11
The idea behind it
NCERT § "Buffer Solutions"
- A buffer resists change in pH when small amounts of acid or base are added or when it is diluted.
- An acidic buffer is a weak acid with its salt of a strong base (acetic acid and sodium acetate); a basic buffer is a weak base with its salt of a strong acid (ammonia and ammonium chloride).
- pH of an acidic buffer: pH = pKa + log([conjugate base]/[acid]) (Henderson-Hasselbalch equation).
- pOH of a basic buffer: pOH = pKb + log([conjugate acid]/[base]), and pH = 14 − pOH at 298 K.
- When the acid and its conjugate base are present at equal concentrations, pH = pKa.
- A buffer can also be made by partly neutralising a weak base with a strong acid: mixing 3 mmol of NH₃ with 1 mmol of HCl leaves 2 mmol NH₃ and 1 mmol NH₄⁺, a basic buffer.
- Within a buffer only the ratio of amounts matters, so millimoles can be used directly without dividing by the total volume.