Rucete ✏ Chemistry In a Nutshell
1. What Is Titration?
- Titration is a lab technique used to determine the concentration of an unknown acid or base by reacting it with a known concentration of base or acid.
2. Titration Formula
MaVa = MbVb
Where:
- Ma, Mb: molarity of acid and base
- Va, Vb: volume of acid and base
- Equation is based on moles of acid = moles of base at the equivalence point.
3. Titration Curve
- A graph of pH vs. volume of titrant added.
- Shows the pH change throughout the titration.
- Key regions on the curve:
- Initial pH: depends on the starting acid or base.
- Buffer region: gradual pH change due to presence of a conjugate acid–base pair.
- Equivalence point: steep rise in pH; moles of acid = moles of base.
- After equivalence: excess titrant determines pH.
4. Types of Titration Curves
Strong Acid + Strong Base
- Equivalence point at pH = 7.
- Sharp, symmetrical pH curve.
Weak Acid + Strong Base
- Starts with higher pH than strong acid.
- Buffer region present before equivalence point.
- Half-equivalence point:
- pH = pKa
- Conjugate acid–base pair concentrations are equal.
- Equivalence point > pH 7
Weak Base + Strong Acid
- Similar to above, but inverted.
- Equivalence point < pH 7
Diprotic Acid (e.g., H₂CO₃)
- Has two equivalence points.
- First equivalence point ≈ pKa₁
- Second equivalence point ≈ pKa₂
5. Indicators
- A chemical indicator (like phenolphthalein) is used to visually signal the equivalence point by changing color.
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Chemistry in a nutshell