Transcript Acid Base Reactions and Titration Curves

Acid Base Reactions and
Titration Curves
Vocab
• Titrant
• Analyte
• Endpoint/Equivalence point
• Indicators
Common Indicators
Name
Acid
color
pH range
Base color
Methyl violet
Yellow
0 – 1.6
Blue-violet
Methyl orange
Red
3.2-4.4
Yellow
Litmus
Red
5-8
Blue
Phenolphthalein
Colorless
Thymolphthalein
Colorless 9.4-10.6
8.2 - 10.0
Pink
Blue
Phenolphthalein
Formal name: 3,3-bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone,
3,3-bis(4-hydroxyphenyl)phthalide)
Bronsted Acid
(colorless, in acid)
Conj. Base
(pink, in base)
Types of Reactions
1. Strong Acid - Strong Base
2. Weak Acid - Strong Base
3. Strong Acid - Weak Base
1. Strong Acid - Strong Base
• Example: HCl + NaOH -->
• Titration Equation: Ma • Va = Mb • Vb
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Equivalence Pt
pH = ____
If 50. mL of HCl was titrated with 0.050 M NaOH,
what is the [HCl]
A 25. mL sample of HCl titrated using 50 mL of 0.050 M NaOH.
Sketch this curve.
pH
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Volume of Base Added
2. Weak Acid - Strong Base
• Example: CH3COOH + NaOH -->
• MV=MV
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pH
2. Weak Acid - Strong Base
Important Points
• pH = pKa when halfway to equivalence
point
• The formation of a conjugate base Awill make the solution BASIC at
equivalence, so pH > 7
3. Weak Base - Strong Acid
• Example: NH3 + HCl -->
• MV=MV
pH = pKb
pH
12.5
3. Weak Base - Strong Acid
Important Points
• pH = pKb at halfway to equivalence
point
• The formation of a conjugate acid BH+
will make the solution ACIDIC at
equivalence, so pH < 7
Titration of Diprotic Acids
2 equivalence pts