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Acid-Base Neutralization Reactions
For simplification, H₃O⁺ will be written as H⁺ for equations. Shown in net ionic equations.
The net ionic equation for a strong acid-strong base would be:
H⁺ (aq) + OH⁻ (aq) → H₂O (l)
The cation associated with OH⁻ is a spectator ion.
The anion (conjugate base) associated with the H⁺ is a spectator ion.
The net ionic equation for a weak acid-strong base would be:
HA (aq) + OH⁻ (aq) ⇌ H₂O (l) + A⁻ (aq)
The cation associated with OH⁻ is a spectator ion.
Weak acids don't completely dissociate.
The net ionic equation for a strong acid-weak base would be:
H⁺ (aq) + B (aq) ⇌ H₂O (l) + HB⁺ (aq)
The anion (conjugate base) associated with the H⁺ is a spectator ion.
Weak bases don't completely dissociate.
Introduction to Buffer Systems
A solution's buffer system resists changes in pH by neutralizing added acids or bases.
Buffer systems typically include:
Weak acid (HA) and its conjugate base (A⁻).
Weak base (B) and its conjugate acid (HB⁺).
Note that conjugate ions typically come in salt form.
The mechanism of buffer systems is that:
Acids/conjugate acids donate protons into the solution in response to the addition of bases.
Bases/conjugate bases accept protons from the solution in response to the addition of acids.
As long as the buffer components aren't used up, the system effectively resists sharp changes in pH.
Calculating pH of Buffer Systems
The pH of an acid buffer solution can be determined using the Henderson-Hasselbalch equation:
Modified Henderson-Hasselbalch Equation for Basic Buffers:
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