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Titrations. . .

Titrations. . . .help you ‘see’ neutralization reactions. Acid and base react to form salt and water. . . .determine concentration of a solution by reacting it with a solution with a known concentration. Types of Titrations. Strong Acid with Strong Base Strong Base with Strong Acid

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Titrations. . .

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  1. Titrations. . . . . .help you ‘see’ neutralization reactions. Acid and base react to form salt and water. . . .determine concentration of a solution by reacting it with a solution with a known concentration.

  2. Types of Titrations • Strong Acid with Strong Base • Strong Base with Strong Acid • Weak Acid with Strong Base • Weak Base with Strong Acid • Weak Acid with Weak Base

  3. Standard Procedure. . . • 1. Prepare standard (titrating solution): it is of known concentration • Exactly mass • This information will be crucial to all other calculations. • Rinse buret • So there is no contamination from other substances. • Fill buret • 2. Unknown: in beaker or flask beneath buret • indicator is added • Known volumes of standard are added to it.

  4. 3. Record data. . . either • volume of standard • Time • pH • Continue until you reach the stoichiometric point: • Moles H+from acid = moles OH- from base. • Stoichiometric point is the equivalence point • pH = pKa • End point – one drop of base beyond stoichiometric/equivalence point; color changed; on graph:midpoint of most vertical part of graph = exact midpoint; rate of pH diminishes; • 4. REPEAT

  5. http://www.shsu.edu/%7Echm_tgc/sounds/titrate.mov

  6. Vocabulary • equivalence point - when the moles of acid or base added equals the moles of acid or base which are present • midpoint - when the moles of acid or base added is 1/2 the moles of acid or base which are present • indicator - a dye used to indicate when the reaction is complete. It changes color at the equivalence point.

  7. Important Regions • At time = 0, before the titration begins • Before the equivalence point • At the midpoint • At the equivalence point • After the equivalence point

  8. Standardizing a Solution. . . • Why is there a need to standardize NaOH? • Mole ratio between KHP and NaOH should be 1:1 (at equivalence point of titration)

  9. Strong Acid / Strong Base

  10. Strong Acid/ Strong Base • Assume 100% ionized in aqueous solution.

  11. Indicators. . .

  12. Compare Weak/Strong Acid

  13. Indicators. . .

  14. Graph shows a steep rise or endpoint for each of the protons in the acid. Diprotic Acid

  15. Weak Acid/Strong Base

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