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Titration

Titration. Titration. Strong acids ionize almost completely Weak acids don’t ionize very much [H 3 O +1 ] not same as acid concentration. [H 3 O +1 ]. Can’t be measured directly Determined by comparison. Acid-Base Titration. Carefully controlled neutralization reaction

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Titration

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  1. Titration

  2. Titration • Strong acids ionize almost completely • Weak acids don’t ionize very much • [H3O+1] not same as acid concentration

  3. [H3O+1] • Can’t be measured directly • Determined by comparison

  4. Acid-Base Titration • Carefully controlled neutralization reaction • Requiresstandard solution& acid-base indicator • Standard solution is: acid/base of known concentration

  5. Titration • Standard solution slowly added to unknown solution • As solutions mix: • neutralization reaction occurs • Eventually: • enough standard solution is added to neutralize the unknown solution Equivalence point

  6. Equivalence point total # moles H+1 ions donated by acid = total # moles H+1 accepted by base total moles H+1 = total moles OH-1

  7. Titration • End-point = point at which indicator changes color • if indicator chosen correctly: • end-point very close to equivalence point

  8. 14- Equivalence Pt    0 ml 20 ml Titration of a strong acid with a strong base Phenolphthalein Color change: 8.2 to 10  pH 7- 0-  Volume of 0.100 M NaOH added (ml) 40ml

  9. MH+1VH+1 = MOH-1VOH-1 • MH+1 = molarity of H+1 • MOH-1 = molarity of OH-1 • VH+1 = volume of H+1 • VOH-1 = volume of OH-1

  10. MaVa = MbVb • True for: • monoprotic acids with monohydroxy bases • diprotic acids with dihydroxy bases • triprotic acids with trihydroxy bases

  11. ≠ # OH’sin base If: # H’sin acid (Ma)(Va) = (Mb)(Vb) need to modify equation: (#H’s) (#OH’s)

  12. Titration Problem #1 • In a titration of40.0 mLof a nitric acid solution, the end point isreached when35.0mLof0.100MNaOHis added Calculate the concentration of the nitric acid solution

  13. Neutralization Reaction • HNO3 + NaOH  H2O + NaNO3 • HNO3 is a monoprotic acid • NaOH is a monohydroxy base

  14. Variables • Ma = ? • Va = 40.0 mL • Mb = 0.100 M • Vb = 35.0 mL

  15. Plug and Chug (1)(X) (40.0 mL) = (0.100 M )(35.0mL)(1) X = 0.875 M HNO3

  16. Titration Problem #2 • What is the concentration of a hydrochloric acid solutionif50.0 mLof a0.250M KOHsolution is needed to neutralize20.0mL of the HCl solutionof unknown concentration?

  17. Neutralization Reaction • KOH + HCl  H2O + KCl • HNO3 is a monoprotic acid • KOH is a monohydroxy base

  18. Variables • Ma = X • Va = 20.0 mL • Mb = 0.250 M • Vb = 50.0 mL

  19. Plug and Chug (1)(X)(20.0 mL) = (0.250 M) (50.0 mL)(1) X = 0.625 M HCl

  20. Titration Problem #3 • What is the concentration of a sulfuric acid solutionif50.0mL of a 0.25 M KOHsolution is needed to neutralize20.0mL of the H2SO4 solutionof unknown concentration?

  21. Neutralization Reaction • H2SO4 + 2 KOH  2 H2O + K2SO4 • H2SO4 is a diprotic acid • KOH is a monohydroxy base

  22. Variables • Ma = X • Va = 20.0mL • Mb = 0.25M • Vb = 50.0mL

  23. Plug and Chug (2)(X)(20.0ml) = (0.25M)(50.0ml)(1) X = 0.3125 MH2SO4(sulfuric acid)

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