Determination Of Calcium Pestils Using The Complexometric Titration Method

Calcium is an essential element for the growth and development of teeth and bones. Most of the Calcium is gained from cereals, fruits and vegetables, these foods are known to have around 10 mg of Calcium per 100 grams. A predominantly eminent intake in childhood Calcium is responsible for the bone mass in adults and it also affects the rate of bone growth. Lentils are a great source of naturally available Calcium. The regular intake of Calcium can reduce the risks of Osteoporosis, a disease where bones start to become fragile (bone thinning) with the passage of time this disease can be responsible for bone fracture.
In this experiment I will determine the Calcium content in five different lentils using the Complexometric Titration method with
Ethylenediaminetetraacetic acid (EDTA). The EDTA is a hexaprotic ion (Chelating agent) this implies that oxygen in acid and Nitrogen in amine can donate a pair of electrons by binding with the metal ions i.e. Forming complex ions with Calcium.
Ca+2 + EDTA→ Ca [EDTA]-4

The equation above shows that EDTA combines with Calcium in a fixed 1:1 molar ratio.
In this experiment a solution containing the free metal ions (Calcium ions) with chelating agent in it will be titrated against a MgCl2 solution. The end point of titration is determined by adding Eriot Black T Indicator, since it forms a colored complex with free metal ions the addition of this turns the color of solution turns blue which is turned into Pink/Violet as the end point of titration is reached.

Figure 1: Showing the Chemical structure of EDTA Figure 2: Showing how EDTA bonds with the Calcium ions. Images taken: http://www.chm.bris.ac.uk/motm/edta/edtah.htm, https://en.wikipedia.org/wiki/Nitrilotriacetic_acid

Research Question:
The determination of Calcium content in Five different Lentils using Complexometric Titration with Ethylenediaminetetraacetic acid (EDTA).
Variables:
Independent Variable:

1) The type of Lentil used ( Split Bean, Split Mung Bean, Brown Lentils, Red Lentils, Yellow Beans) Dependant Variable:

1) Calcium content in every bean/Lentil.
2) Amount of MgCl2 added will dependent on the type of Lentils/Bean
Controlled
Variables:
1) The Quantity of Lentil/ Beans used (Same quantity of every bean will be used)
2) The same amount of EDTA, Buffer, Eriot Black T Indicator will be used for Trials with every Lentil/Beans.

Equipment Needed:
Burette
20 mL Pipette
100, 250 and 500 mL Conical Flasks
100 mL Volumetric Cylinder
Rubber Gloves
Fume Cupboard (For Ammonia)
Electric Weight Machine
Spatula and Glass rod
150 mL Beaker
Retort Stand
Conical Flask
PH Meter

Solutions Needed:
EDTA Solution: A solution of 500mL of a 0.05 molL-1 will be made. Weight 10 g of EDTA salt and standardize it up to the mark in a 500mL Volumetric Flask. Distilled water was used to make the solution.
Buffer: Dissolve 7.0 g of Ammonium Chloride powder in 58mL of concentrated ammonia. Standardize it up to 100mL with distilled water in a Volumetric Cylinder. The PH of the solution should be between 10.5-11
MgCl2.6H2O: 0.0025 molL-1 solution. Weight 2.45 g of Magnesium Chloride Hexahydrate and standardize it up to 500mL with distilled water in a Volumetric Flask.
Eriochrome Black T Indicator: Dissolve 0.3 g of Eriochrome Black T Indicator in 15.01mL of concentrated ammonia and 5.04mL of absolute Ethanol