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Acid-Base Titrations 14.3

Acid-Base Titrations 14.3. Calculations involving neutralization reactions. Learning Objectives. Understand the neutralization reaction … strong acid and base reaction Concept of titration, end point, and equivalence point and how they relate to neutralization reaction

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Acid-Base Titrations 14.3

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  1. Acid-Base Titrations 14.3 Calculations involving neutralization reactions

  2. Learning Objectives • Understand the neutralization reaction … strong acid and base reaction • Concept of titration, end point, and equivalence point and how they relate to neutralization reaction • How to solve titration problems … how to determine unknown acid or base concentration

  3. Neutralization Reaction • Acid + Base  Salt + Water • Called a neutralization reaction • Is a double replacement reaction • Requires use of an indicator to identify neutralization point • Strong acid + Strong base = neutral solution • If # of H+ = # of OH-

  4. Titration • A titration is a reaction where a solution of known concentration (standard solution) is used to identify a solution of unknown concentration

  5. Practical Examples of Titrations • Determining blood glucose levels. • Determination of medical proportions in a IV drip. • Amount of salt and sugar in food. • Level of acidity in wine and cheese. • Level of acidity in fresh water samples.

  6. End Point • The end point of a titration is when the solution just barely changes color • The equivalence point is the point where the acid and base exactly react with one another • Ideally, the end point should be the same as the equivalence point

  7. Titration Calculation In a titration, 27.4 ml of a 0.0154 M HCl solution is added to 20.0 mL sample of NaOH solution of unknown concentration. What is the molarity of the basic solution? HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) SA SB Neutralization First we need to figure moles of HCl used to neutralize NaOH in reaction. 0.0274 L x 0.0154 mol/L = 4.22 x 10-4 mol of HCl

  8. Titration Calculation = 4.22 x 10-4 mol of HCl HCl(aq) + NaOH(aq) H2O(l) + NaCl(aq) = 4.22 x 10-4 mol of NaOH M of NaOH = 4.22 x 10-4 mol of NaOH .0200 L M of NaOH = .021 M

  9. Titration Endpoint How can you tell when you have added enough NaOH?

  10. Titration Curve

  11. Titration Calculation Shortcut • Objective: to find the M of the unknown acid or base. • Use a balanced chemical equation to determine the mole/mole ratio of acid to base. MaVana=MbVbnb • M = molarity • V = volume • n = # of H3O+ ions in the acid or OH- ions in the base. (if there are no OH- ions in the base, n = 1)

  12. Weak Acid-Strong Base HC2H3O2(aq) + NaOH(aq) H2O(l) + C2H3O2-(aq) WA SB CB HC2H3O2(aq) + OH-(aq) C2H3O2-(aq) WA CB SB Only basic salt is left when we reach equivalence point, therefore the final pH of solution must be basic.

  13. Strong Acid-Weak Base H3O+(aq) + NH3(aq) H2O(l) + NH4+(aq) SA WB CA H+(aq) + NH3(aq) NH4+(aq) CA SA WB Only acidic salt is left when we reach equivalence point, therefore the final pH of solution must be acidic. Note: For strong acid and strong base titration, pH should be close to 7 at equivalence point.

  14. Cool Down • How many moles of sulfuric acid are required to completely neutralize 0.50 mol of sodium hydroxide? • How many ml of 0.56 M potassium hydroxide are needed to completely neutralize 150.0 ml of a 1.56 M of phosphoric acid?

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