Intro:
Minerals found in molds and vegetables are important for proper dental and calcium (Ca) development. Eating calcium during childhood is important in determining bone density in adults, and also affects rates. Dairy products provide the best sources of calcium in bioavail and can reduce osteoporosis through increased use, a disease that affects many people around the world when bones undergo brittle (bone dilution), leading to bone fractures over time.
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Experiment Measuring Calcium Ions in Milk
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In this experiment, the calcium content in milk is measured by EDTA back titration. It means that one acid and one amine nitrogen can donate to one electron. EDTA is a hexaprotic ion (chair agent): it acts by binding metal ions (e.g. a complex of calcium ion). The chemical equation reveals that EDTA in the reaction of Ca is 1: 1 molar. Using a solution that includes a free metal ion (e.g. calcium) and a chelating agent solution (EDTA) this titanium transfer is measured against a normal Ca2 + ion solution. The final point is usually determined using a color-coded reference ligator with a free metal color indicating the difference in green / brown color. Personally, I want to see this as I want to know how much dairy products give your life so much calcium.
Figure 1: The EDTA Molecule
Image taken from: http://www.chm.bris.ac.uk/motm/edta/EDTA.gif [Accessed 11/28/19]
Figure 2: How it bonds with the calcium ions
Image taken from: http://openlearn.open.ac.uk/file.php/2986/S_ 1_002i.jpg[Accessed 11/28/19]
Experimental:
Results:
Showing the mass of milk used.
Sample #
1
2
3
Mass of empty glass in grams
115
90
144
Mass of powder and glass in grams
116
91
135
Mass of milk used in grams
1
1
1
Showing the masses of EDTA and CaCO3 used.
EDTA
CaCO3
Mass of empty beaker /g
32.1
32.1
Mass of beaker and salt /g
35.8
32.7
Mass of salt used /g
3.70
0.615
EDTA mass calculation needed to make the solution
EDTA: 372 g/mol-1
Number of moles = 0.03 mol
Therefore mass of salt required for 25mL = (372 g/mol-1×0.03 mol)/4
The Mass of EDTA = 2.79g
CaCO3 Regular Solution Volumes versus 25mL 0.03 Molarity EDTA and Dairy Solutions
Sample #
1
2
3
Initial Analysis in cm3
1.0
0.0
0.0
Final Analysis in cm3
39
38
37
Volume of CaCO3 in cm3
38
38
37
CaCO3 Regular Solution Volumes volumes versus 25mL 0.03 Molarity EDTA.
Sample #
1
2
3
Initial Analysis in cm3
0.0
0.0
0.0
Final Analysis in cm3
40
41
41
Volume of CaCO3 in cm3
40
41
41
Treatment of Results:
Concentration of EDTA
Mass of EDTA = 2.79g | Mole Raito of EDTA: 372 g/mol-1
Number of moles EDTA = 0.03 mol | Number of moles of EDTA present in 250mL
Moles = m/mole raito = 2.79g/372 g/mol-1 = 7.5 x10-3 mol
So there are 7.5 x10-3 moles in the 250mL solution.
Concentration = (7.5 x10-3 moles/250mL) x 1000 = 0.03 Molarity
Concentration of CaCO3
Mass of CaCO3 = 0.615g | Mole Raito CaCO3: 100 g/mol-1
Number of moles of CaCO3 present in 250mL
= 0.615g/100g/mol-1= 6.15 x10-3 mol
So there is 6.15 x10-3 mol present in 250mL of solution
Concentration = (6.15 x10-3 mol/250mL) x 1000 = 0.0246 Molarity
Finding the number of Ca moles that reacted to EDTA with 25 mL
Sample Blank 1 used 40mL of CaCO3
So in 40mL there is (0.0246M/1000) x 40mL = 9.84×10-4 mol used
9.84×10-4 mol of Ca reacted with 25mL of EDTA
Sample 1 used 38mL of CaCO3
So in 38mL there is (0.0246M/1000) x 38mL = 9.35×10-4 mol used
9.35×10-4 mol of Ca reacted with 25mL of EDTA
Therefore the number of moles of calcium in sample 1
= Total calcium reacting with 25 mL of EDTA – moles of calcium reacting with residual moles of calcium = 9.84×10-4 mol – 9.35×10-4 mol = 4.9 x10-5 mol
To find the % of Ca in milk sample 1
Mole Raito Ca = 40.1 g/mol-1
= 4.9 x10-5 moles x 40.1 g/mol-1 = 1.96 x10-3 g in 1 g of milk
So the amount of Ca in 100g of milk = 196mg
Average calcium concentration = (196mg + 373mg+5\324)/3 = 190mg
So the standard deviation = 13.8. So the calcium concentration in milk samples = 190 ±13.8 mg
Conclusion: This lab has shown how calcium can be present in milk. Calcium, theoretically, reaches 900-1190 mg per 100 g of milk powder. The mass was 190 ± 13.8 mg in this experiment. The scale shows a high error rate and cannot be precise because the sample used did not show the exact value.
Discussion: The empty tithes in which Solochrome Black is used as a guide show the color difference with the introduction of calcium-EDTA. At the center, the solutions of Royal Blue (Ca2 + ion with a reference) were very ahead of the endpoint. Eventually, the center turned purple (all Ca2 plus EDTA ions are complex, an indicator that has not been completely changed). In the experiment, a color change was also observed when the blue sample solutions started well before the end, with clouds (opaque) gray, then before the end point, followed by a violet color. Overall, milk is probably the safest way to get your required amount of calcium to keep your teeth and bones strong and healthy.
References:
CHEM 2460 Principles of Chemical Analysis Laboratory Manual.pg 17-21
James N Miller & Jane C Miller, “Statistics and Chemometrics for Analytical” Chemistry, 5th Ed(2005) Publ. Pearson Education Limited pg 114
http://www.csudh.edu/oliver/che230/labmanual/calcium.htm [Accessed 11/28/19]
WO SAY DISCUSSION HELP http://www.ajcn.org/cgi/reprint/83/2/310.pdf [Accessed 10/04/10]
http://www.cerlabs.com/experiments/10875404367.pdf[Accessed 11/28/19]
Cassie. “The Determination of Calcium in Milk by EDTA Titration.” Scribd, Scribd, 27 Apr. 2010, www.scribd.com/doc/30580869/The-Determination-of-Calcium-in-Milk-by-EDTA-Titration.
