4 Classes of Reactions
Used quantitatively
Precipitation
Gravimetric Ca: calcium oxalate
Acid/Base
Volumetric Acid: KHP + OH ¯
Redox
Gasiometric Nitrite:
NO2- + H+ NH2SO3¯ → N2 + HSO4¯ + H2O
Complexation
This lab
Volumetric Ca & Zn: EDTA
1
Volumetric Determination of Zinc and Calcium
Using Complexometric Titration
First Week:
1) Preparation and Standardization of EDTA solution
(10ppt)
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!!!
2) Analyze Cold-Eeze Lozenge for Zn2+
3) Check-in & Course Evaluations
2
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.
3
Polydentate or Multidentate Ligands
Like :NH3
1 Ligand, but
2 bonds
Like CO32-
Called Chelates (claw)
4
- 2
O
1
- O
O O
5
.. N
..
N
O 6
O-
O- 3
4
O
Fully deprotonated EDTA can bind to metal ion at 6 sites
5
6
Indicator
InMetal complex is one color
Add EDTA → EDTAMetal
At endpoint: InH a different color
Make mock solution for comparison
Note that there are 2 different indicators- one for
Ca and one for Zn
7
Week 1 – Standardize CaCO3
Prepare 500 ml of a 0.020 M EDTA solution
Use 250 ml volumetric flask to the mark emptying into a clean 800 mL
beaker, repeat. Dissolves slowly (> 5 min). Heat if necessary but
cool before titrating.
Preparation of the CaCO3 in volumetric flask
Also, after titrating, use SciFinder Scholar or Web of
Science in 113.
8
Week 2 – Water and Lozenge Analysis
Make buffer solution
Titrate water samples
Water hardness results go to Prof.Reinen of Geology
Titrate three lozenges
Make sure to take masses of each before crushing with
mortar & pestal and determine amount used in each
titration
9