Acids and Bases Lesson 1 Acid & Base Properties (Strong & Weak acids)
Titration. strong acids ionize almost completely weak acids don’t ionize very much [H 3 O +1 ] not...
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Transcript of Titration. strong acids ionize almost completely weak acids don’t ionize very much [H 3 O +1 ] not...
![Page 1: 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 ] not same as acid.](https://reader034.fdocuments.us/reader034/viewer/2022051820/56649efe5503460f94c1350f/html5/thumbnails/1.jpg)
Titration
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• strong acids ionize almost completely
• weak acids don’t ionize very much• [H[H33OO+1+1] ] notnot same as acid same as acid
concentrationconcentration
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[H3O+1]
• can’t be measured directly
• determined by comparison
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Acid-Base Titration
• carefully controlled neutralization rxncarefully controlled neutralization rxn• requires:requires:
– standard solutionstandard solution & – acid-base indicatoracid-base indicator
• standard solution is: acid/base of knownknown concentration
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TitrationTitration
• 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 pointequivalence point
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Equivalence pointEquivalence point
total # moles H+1 ions donated by acid =
total # moles H+1 accepted by base
so: total moles H+1 = total moles OH-1
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TitrationTitration
• end-pointend-point: point at which indicator changes color
– if indicator chosen correctly: • end-point very close to equivalence point
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Titration: strong acid with strong base
volume of 0.100 M NaOH added (ml)
pH
0-
14-
7- equivalence pt
phenolphthalein phenolphthalein color change: color change: 8.28.2 to 10 to 10
0 ml
40ml
20 ml
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MMH+1H+1VVH+1H+1 = M = MOH-1OH-1VVOH-1OH-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
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MaVa = MbVb
• [true for:– monoprotic acids with monohydroxy bases
– diprotic acids with dihydroxy bases
– triprotic acids with trihydroxy bases]
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IF:
# H’s in acid
(Ma)(Va) = (Mb)(Vb)
≠ # OH’s in base
need to modify equation:
(#H’s) (#OH’s)
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Titration Problem #1
In a titration of 40.0 mL40.0 mL of a nitric acid solution, the end point was reached when 35.0mL35.0mL of 0.100M0.100M NaOHNaOH was added.
calculate the concentration of the calculate the concentration of the nitric acid solutionnitric acid solution
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Neutralization Reaction
HNO3 + NaOH H2O + NaNO3
•HNO3 is a monoprotic acid
•NaOH is a monohydroxy base
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Variables
• Ma = ?
• Va = 40.0 mL
• Mb = 0.100 M
• Vb = 35.0 mL
• #H’s = #OH’s = 1
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Plug and Chug
(1)(x) (40.0 mL) = (0.100 M )(35.0mL)(1)
X = 0.875 M HNO3
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Titration Problem #2
• What is theWhat is the concentration concentration of aof a hydrochloric acid solutionhydrochloric acid solution if 50.0 mL50.0 mL of a 0.250M KOH0.250M KOH solution is needed to neutralize 20.0mL 20.0mL of anof an HCl HCl solutionsolution of unknown concentration?
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Neutralization Reaction
KOH + HCl H2O + KCl
•HNO3 is a monoprotic acid
•KOH is a monohydroxy base
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Variables
• Ma = X
• Va = 20.0 mL
• Mb = 0.250 M
• Vb = 50.0 mL
• #H’s = #OH’s = 1
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Plug and Chug
(1)(X)(20.0 mL) = (0.250 M) (50.0 mL)(1)
X = 0.625 M HCl
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Titration Problem #3
• What is theWhat is the concentration concentration of aof a sulfuric acid solutionsulfuric acid solution if 50.0mL 50.0mL of aof a 0.25 M KOH0.25 M KOH solution is needed to neutralize 20.0mL 20.0mL of theof the H H22SOSO44 solutionsolution of unknown concentration?
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Neutralization Reaction
• H2SO4 + 2 KOH 2 H2O + K2SO4
• H2SO4 is a diprotic acid
• KOH is a monohydroxy base
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Variables
• Ma = X
• Va = 20.0mL
• Mb = 0.25M
• Vb = 50.0mL
• #H’s = 2
• #OH’s = 1
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Plug and Chug
(2)(X)(20.0ml) = (0.25M)(50.0ml)(1)
X = 0.3125 M H2SO4(sulfuric acid)