PURPOSE:
• To standardize a solution of sodium hydroxide
by titration with a primary standard,
potassium hydrogen phthalat...
Use ph electrode
ANALYTICAL CHEMISTRY
• Determination of iron in a razor blade
• Determination of acetic acid in vinegar
• Determination of...
Must do three things before You start
• 1. Clean the Buret
• 2. Delivering Solution from the Buret
• 3. Filing the Buret f...
KHP
Why use KHP?
• The hydrogen is slightly acidic, and it is often
used as a primary standard for acid-base
titrations becaus...
as a buffering agent
• As a weak acid hydrogen phthalate reacts
reversibly with water to give hydronium (H3O+)
and phthala...
What I would like . . .
• In this experiment you will determine the
amount of acid needed by titration with the
strong bas...
What is a standardization???
• Since it is hard to prepare a NaOH solution of
accurately known concentration directly
from...
Excellent to use!!!
Can actually obtain 1 mole of H+
by using a balance
A titration
• Knowing the volume of titrant added allows
the determination of the concentration of the
unknown. Often, an ...
acid-base indicator
• An acid-base indicator is itself a weak acid (or
its conjugate base).
• An acid-base indicator is a ...
phenolphthalein
phenolphthalein
• Phenolphthalein
• Type: HIn + H2O <->In- + H3O+
pK: 9.5
Approximate pH range for color change:
• 8.0-9.8...
phenolphthalein
Commonly used equipment
• Buret
• Erlenmeyer Flask
• Magnetic Stir Plate
• Electronic Balance
accuracy
• The accuracy of the results of your
titration will be a reflection of the
care you took while performing it.
Wh...
accuracy
• SOMETIMES!!!!!!!
• Titrations of unknown solutions are done in
two steps: a scout titration used to determine
t...
What You will do . . .
• An 0.8167 gram sample of primary standard
KHP (assay = 99.95%) required 38.25 mL of
NaOH to neutr...
Goto pdf. . . .
• Path:
XXXX g sample -> g KHP -> mol KHP ->
mol NaOH -> M NaOH
path
0.8167 g sample x (99.95g KHP)/(100 gram)
x (1molKHP)/(204.22g KHP)
x (1mol NaOH)/(1 mol KHP)
x (1 )/(0.03825 L)=
0.1...
Using the pH Probe
Using the pH Probe
• Using the pH Probe
• Preparation of the pH Sensor
• A pH sensor connected to a computer will be
used ...
Using the pH Probe
Best site
• http://www.chemistry.mtu.edu/~djchesne/cla
sses/ch2212/Tutorials/Vernier_pH_tutorial.ht
m
Arrhenius acids.
The net ionic equation
H + (aq) + H2O(l) <-> H3O + (aq)
• Pure water already contains small quantities
of the H + ion (pro...
On Exam
• Example: Calculate the weight of primary
standard potassium hydrogen phthalate
• (assay = 99.95%) that would be ...
• Example: An 0.8167 gram sample of primary
standard KHP (assay = 99.95%) required
• 38.25 mL of NaOH to neutralize. Calcu...
• Example: A 1.7734 gram sample of KHP
required 40.11 mL of 0.1036 N for titration.
• Calculate the assay of the KHP and r...
Khpacidbaseneutralization1slideonechm240xxxxxxxxxxxxxxxxxxdontletgo2 140110101250-phpapp02
Khpacidbaseneutralization1slideonechm240xxxxxxxxxxxxxxxxxxdontletgo2 140110101250-phpapp02
Khpacidbaseneutralization1slideonechm240xxxxxxxxxxxxxxxxxxdontletgo2 140110101250-phpapp02
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Khpacidbaseneutralization1slideonechm240xxxxxxxxxxxxxxxxxxdontletgo2 140110101250-phpapp02

  1. 1. PURPOSE: • To standardize a solution of sodium hydroxide by titration with a primary standard, potassium hydrogen phthalate (KHC8H4O4)
  2. 2. Use ph electrode
  3. 3. ANALYTICAL CHEMISTRY • Determination of iron in a razor blade • Determination of acetic acid in vinegar • Determination of Alcohol in Blood
  4. 4. Must do three things before You start • 1. Clean the Buret • 2. Delivering Solution from the Buret • 3. Filing the Buret for a titration • 4. Preparing the KHP Sample • 5. Titrating the KHP • * Must use Your Lab book today! • *** This is one of the MOST complicated labs
  5. 5. KHP
  6. 6. Why use KHP? • The hydrogen is slightly acidic, and it is often used as a primary standard for acid-base titrations because it is solid and air-stable, making it easy to weigh accurately. It is not hygroscopic. It is also used as a primary standard for calibrating pH meters
  7. 7. as a buffering agent • As a weak acid hydrogen phthalate reacts reversibly with water to give hydronium (H3O+) and phthalate ions. HP- + H2O <->P2- + H3O+ • KHP can be used as a buffering agent(in combination with hydrochloric acid (HCl) or sodium hydroxide (NaOH) depending on which side of pH 4.0 the buffer is to be)
  8. 8. What I would like . . . • In this experiment you will determine the amount of acid needed by titration with the strong base NaOH.
  9. 9. What is a standardization??? • Since it is hard to prepare a NaOH solution of accurately known concentration directly from the solid, you will need to standardize your NaOH solution against a precisely weighed amount of standard acid. • The acid used is the weak monoprotic acid, potassium hydrogen.
  10. 10. Excellent to use!!! Can actually obtain 1 mole of H+ by using a balance
  11. 11. A titration • Knowing the volume of titrant added allows the determination of the concentration of the unknown. Often, an indicator is used to usually signal the end of the reaction, the endpoint
  12. 12. acid-base indicator • An acid-base indicator is itself a weak acid (or its conjugate base). • An acid-base indicator is a weak acid having a different colour in aqueous solution from its conjugate base.
  13. 13. phenolphthalein
  14. 14. phenolphthalein • Phenolphthalein • Type: HIn + H2O <->In- + H3O+ pK: 9.5 Approximate pH range for color change: • 8.0-9.8 Color of acid form: clear Color of base form: red-violet
  15. 15. phenolphthalein
  16. 16. Commonly used equipment • Buret • Erlenmeyer Flask • Magnetic Stir Plate • Electronic Balance
  17. 17. accuracy • The accuracy of the results of your titration will be a reflection of the care you took while performing it. When done carefully, titrations give very accurate, precise results. •
  18. 18. accuracy • SOMETIMES!!!!!!! • Titrations of unknown solutions are done in two steps: a scout titration used to determine the approximate amount of titrant needed followed by the actual titration that you will use to make your calculations.
  19. 19. What You will do . . . • An 0.8167 gram sample of primary standard KHP (assay = 99.95%) required 38.25 mL of NaOH to neutralize. Calculate the molarity of the NaOH solution.
  20. 20. Goto pdf. . . . • Path: XXXX g sample -> g KHP -> mol KHP -> mol NaOH -> M NaOH
  21. 21. path 0.8167 g sample x (99.95g KHP)/(100 gram) x (1molKHP)/(204.22g KHP) x (1mol NaOH)/(1 mol KHP) x (1 )/(0.03825 L)= 0.1040 M NaOH
  22. 22. Using the pH Probe
  23. 23. Using the pH Probe • Using the pH Probe • Preparation of the pH Sensor • A pH sensor connected to a computer will be used to measure pH. Plug the pH probe into channel 1 of the interface box. Plug the power cord on the interface box into an electrical outlet.
  24. 24. Using the pH Probe
  25. 25. Best site • http://www.chemistry.mtu.edu/~djchesne/cla sses/ch2212/Tutorials/Vernier_pH_tutorial.ht m
  26. 26. Arrhenius acids.
  27. 27. The net ionic equation H + (aq) + H2O(l) <-> H3O + (aq) • Pure water already contains small quantities of the H + ion (proton), H3O + (hydronium ion)
  28. 28. On Exam • Example: Calculate the weight of primary standard potassium hydrogen phthalate • (assay = 99.95%) that would be required to standardize a 0.1 N NaOH solution, • assuming a 40 mL titration. • PATH: L NaOH mol NaOH mol KHP g KHP  g sample • Note that 1 equiv = 1 mol for both KHP and NaOH so N = M and molecular weight = equivalent weight.
  29. 29. • Example: An 0.8167 gram sample of primary standard KHP (assay = 99.95%) required • 38.25 mL of NaOH to neutralize. Calculate the molarity of the NaOH solution. • PATH: g sample g KHP mol KHP mol NaOH M NaOH
  30. 30. • Example: A 1.7734 gram sample of KHP required 40.11 mL of 0.1036 N for titration. • Calculate the assay of the KHP and report with a relative error of 1 part per 1000.

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