1 / 10

Buffered Solutions

Buffered Solutions. What is a buffer? Calculations involving Buffers. What are buffers?. Buffers are solutions of a weak conjugate acid-base pair . They are particularly resistant to pH changes , even when strong acid or base is added. Buffer Solutions.

bell
Download Presentation

Buffered Solutions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Buffered Solutions What is a buffer? Calculations involving Buffers

  2. What are buffers? • Buffers are solutions of a weak conjugate acid-base pair. • They are particularly resistant to pH changes, even when strong acid or base is added.

  3. Buffer Solutions • Consist of a weak acid and its salt • HF and NaF • Consist of a weak base and its salt • NH3 and NH4Cl

  4. How are they resistant to pH changes?How do buffers “work” ? • If we mix a weak acid (HA) with its conjugate base (A-), both the acid and base components remain present in the solution. • This is because they do not undergo any reactions that significantly alter their concentrations. • The weak acid and weak base remain in the solution with high concentrations since they rarely react with the water.

  5. How do buffers “work”? • The acid/conjugate base may react with one another, HA + A- → A- + HA, but when they do so, they simply trade places and the concentrations [HA] and [A-] do not change. • In addition, HA and A-rarely react with water. • Weak acid rarely dissociates in water (will rarely lose its proton H+ to water). • Conjugate base is weak, it rarely steals a proton H+ from water.

  6. Example • A buffered solution contains 0.50 M acetic acid (Ka = 1.8 x 10 -5) and 0.50 M sodium acetate. Calculate the pH of this solution.

  7. Equilibrium and Buffers • pH of Buffers determined by two factors: #1. value of Ka for the weak acid/base (Ka) #2. ratio of concentrations of conjugate acid/ base pair [HA] / [A-] Henderson –Hasselbach Equation

  8. Sample Exercise 17.3 p. 709 • Common Ion Effect, neglect x • LIST • THINK • ICE • SOLVE

  9. Henderson-HasselbachEqn • Can be used when the ratio is known [HA]/[A-] • Can be used when Ka or Kb is known (pKa)

  10. Sample Exercise 17.4 p. 710 • Work Backwards using Kb and [OH-] • Get out Buffers Made Easy Handout! • Let’s watch and learn!

More Related