1 / 10

Indicators and Buffers

Indicators and Buffers. Indicators. Indicators are a substance that change color in the presence of (whatever they check for) They do this because of Le Ch â telier’s principle. All you need an equilibrium reaction with different colored products and reactants.

finn-goff
Télécharger la présentation

Indicators and Buffers

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. Indicators and Buffers

  2. Indicators • Indicators are a substance that change color in the presence of (whatever they check for) • They do this because of Le Châtelier’s principle. All you need an equilibrium reaction with different colored products and reactants. • The pen used to check for counterfeit money is a starch indicator

  3. How an acid base indicator works • A generic indicator will follow this reaction, HId is the reactant indicator, and Id- is its product • HId + H2O  H3O+  + Id- • The color differences are important • in an acidic solution (high H3O+) you see reactant • HId + H2O H3O+  + Id- • in a basic solution (low H3O+) you see product • HId + H2OH3O+  + Id-

  4. Acid Base indicators • Acid base indicators change color at certain pH levels • They don’t have to change at 7 (most don’t) • Universal indicator solution(phenolphthalein, bromthymol blue and methyl red dissolved in ethanol and water) changes color at each integral pH value

  5. Other pH indicators • Litmus and phenolphthalein are indicators • Red cabbage has a pigment that changes colors at different pH values

  6. Buffers • Buffers are solutions that don’t change in pH when acids or bases are added. • They use weak acids/bases and Le Châtelier’s principle. • WA = weak acid • HWA + H2O  H3O+ + WA-

  7. How? • pH is determined by the concentration of H3O+ • Concentration is measured by mol /L • Moles of H3O+ / L (primarily of) H2O

  8. What it does • adding H3O+ forces the equation to the left • so the [H3O+] remains constant • removing H3O+ (adding OH-) forces the equation to the right • so the [H3O+] remains constant • There is a breaking point where the pH will change.

  9. What does this have to do with my life? • Your blood is a buffered solution • The pH must remain between 7.35-7.45 • Outside of that range can kill you • below this range is called acidosis • above is called alkalosis

  10. homework • Read section 10.5 • Pg 354-358 • Questions 26-30; 97-100

More Related