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# Intro to Buffers

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Sections
Intro to Buffers
Henderson-Hasselbalch Equation
Intro to Acid-Base Titration Curves
Strong Titrate-Strong Titrant Curves
Weak Titrate-Strong Titrant Curves
Acid-Base Indicators
Titrations: Weak Acid-Strong Base
Titrations: Weak Base-Strong Acid
Titrations: Strong Acid-Strong Base
Titrations: Diprotic & Polyprotic Buffers
Solubility Product Constant: Ksp
Ksp: Common Ion Effect
Precipitation: Ksp vs Q
Selective Precipitation
Complex Ions: Formation Constant

Acid-Base Buffers resist drastic changes in pH of the solution.

###### Identifying Buffers

Concept #1: Acid-Base Buffers

Acid component of a buffer neutralizes the strong base added to solution, while base component of a buffer neutralizes the strong acid added.

Concept #2: Buffer Creation

3 ways to create a buffer

1. Weak acid or base with its conjugate form.

2. Strong acid with weak base; weak species in higher concentration.

3. Strong base with weak acid; weak species in higher concentration.

Example #1: Select ALL pair(s) that could form a buffer solution.

a) CH3CO2H and HF      b) HNO3 and NH3          c) HCl and NaCl            d) KOH and HCN             e) NaBr and NaOH

Practice: Which pairs of compounds are capable of making a buffer? Select all that apply.

a) 1.3 M LiOH and 1.7 M HCOOH                                               c) 0.35 M CH3CO2H and 0.34 M CH3CO2

b) 0.784 M NH4+ and 0.323 M HClO4                                       d) 0.80 HNO3 and 0.15 MgO

Concept #3: Buffer Capacity

Buffer Capacity is the amount of acid or base a buffer can neutralize before the buffer is all used up.

Example #2: Which of the following combinations would make a buffer with the greatest buffering capacity? (1 L solution.)

a) 0.25 moles HClO2 and 0.20 moles NaClO2                   c) 0.35 moles HNO2 and 0.30 moles KNO2

b) 0.35 moles HClO2 and 0.25 moles NaClO2                   d) 0.50 moles HNO2 and 0.48 moles KNO2

Concept #4: Buffer Range

Buffer Range is a ratio of Weak Acid to Conjugate Base concentrations. Buffer is effective when WA:CB = 10:1 or 1:10.

Example #3: Which of the following combinations would create the most effective buffer?

a) 1.2 M CH3NH2 and 1.0 M CH3NH3+                  c) 0.25 M CH3NH2 and 1.5 M CH3NH3+

b) 1.3 M CH3NH2 and 0.78 M CH3NH3+                d) 0.68 M CH3NH2 and 6.8 M CH3NH3+

Practice: Determine which of the following actions will destroy a buffer composed of 0.50 L of 1.44 M H3PO4 and 0.60 L of 1.25 M NaH2PO4.

a) Addition of 1.45 moles of KH2PO4

b) Addition of 0.85 moles of HCl