Your Lab Final - 21 points

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Your Lab Final - 21 points

• 25-30 min on the last day of lecture, Wed Dec 9
• Short answer multiple choice
• Bring your calculator common sense
• Review your old labs
• Take note of basic calculations (including
  stats), chemical equations, techniques used

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Volumetric Determination of Zinc and
Calcium Using Complexometric Titration First
Week 1) Preparation and Standardization of
EDTA solution (10ppt) save
for week 2 2) Use SciFinder Scholar or Web of
Science to find reference
(page 3) Second Week 1) Analyze Water Sample
for Ca2 You must do
this first!!! Geology will use your data! 2)
Analyze Cold-Eeze Lozenge for Zn2 3) Check-in
Course Evaluations
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4 Classes of ReactionsUsed quantitatively
Precipitation Gravimetric Ca calcium
oxalate Acid/Base Volumetric Acid KHP OH
Redox Gasiometric Nitrite NO2- H
NH2SO3 ? N2 HSO4 H2O Complexation
This lab our final
experiment! Volumetric Ca Zn EDTA
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Development of Cold-Eeze Lozenges
One of the people involved in the designed to
reduce the duration and severity of the common
cold by introducing zinc ions into the body is
J. C. Godfrey
We are going to get one of the references in his
research that talks about this research to
treat the common cold, using Scifinder Scholar
or Web of Science. The Libraries of The
Claremont Colleges
You will do this in the computer room (113) after
completing standardization.
Write down the reference and a one sentence
summary of the abstract in your report.
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Polydentate or Multidentate Ligands
Like NH3
1 Ligand, but 2 bonds
Like CO32-
Called Chelates (claw)
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2
1
5
6
3
4
Fully deprotonated EDTA can bind to metal ion at
6 sites
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Eriochrome Black- T Indicator Deprotonated
indicator (In-) in the presence of excess metal
ions (Mg2) forms a wine-red complex (MgIn-) Add
EDTA ? at the endpoint MgEDTA forms InH
turns greyish blue Make mock solution for
comparison
Note that there are 2 different indicators- one
for Ca2 and one for Zn2
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Week 1 Standardize EDTA

• Prepare 500 ml of a 0.020 M EDTA solution
• Use 250 ml volumetric flask to the mark emptying
  (2x) into a clean 800 mL beaker, repeat.
  Dissolves slowly (gt 5 min). Heat if necessary but
  cool before titrating.

Preparation of the CaCO3 in beaker, transfer to
volumetric flask
Also, after titrating (3 trials, 5-10ppts), use
SciFinder Scholar or Web of Science in 113. If
time permits, titrate water sample (step 3, page
4).
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Week 2 Evaluations, Water and Lozenge Analysis,
Check out

• Titrate water samples
• Water hardness results go to Prof.Reinen of
  Geology
• (obtain 100mL from lab assistant)
• Use 6-7 drops of indicator
• Titrate three lozenges
• Make buffer solution
• Remember to take masses of each before crushing
  with mortar pestal and determine amount used in
  each titration

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How are you going to make the buffer?

• pH pKa log A-/HA where A- acetate ion
  in this case
• HA 0.02500L (1.00M)/0.250L 0.100 M
• pKa (HA) 4.74
• 5.5 4.74 log A-/0.100
• A- 0.5754 M
• n(A-) 0.5754 M (0.2500L) 0.1439 moles
• m(NaA?3H2O) 0.1439 moles (136.08
  g/mole) 19.6 grams for the hydrate
• m(NaA) 0.1439 moles (82 g/mole) 11.8
  grams for the anhydrous salt