Chemistry: To what extend does temperature affects the concentration of calcium ions from tab water, determined by complexometric titration, using Eriochrome Black T indicator ?

To what extent does température affect the concentration of calcium ions from tap water, determined by complexometric titration, using eriochrome black t indicator ?
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To what extent does température affect the concentration of calcium ions from tap water, determined by complexometric titration, using eriochrome black t indicator ?
1 Introduction
1 Personal Engagement
Water is generally referred to as a universal solvent, and it is a vital liquid that helps to support the lives of both plants and animals. Human beings rely on water for their domestic activities. The human body is mainly composed of water, which removes toxic substances in the body, normalizes body temperature, transports oxygen and nutrients into our cells, and helps to maintain homeostasis (Nordin, 2011). According to chemistry, the chemical structure of water comprises of hydrogen and oxygen. Water is classified as hard or soft water, depending on the chemical composition. Hard water is water that is dissolved in various mineral deposits like magnesium and calcium, while soft water contains only sodium ions in the original water structure. The water quality is known to affect the livelihood of people. Soft water is known to be useful when washing and drinking at home. Hard water contains calcium and magnesium minerals that make water hard. The higher the deposits of the calcium and magnesium, the harder the water. It is essential to understand the effects of hard water on the daily activities of human beings like forms scum when used in washing clothes and leaves mineral deposits on tap water, thus creating low pressure in taps.
The human body requires various chemicals for its regular activities. According to different diet guidelines, the body needs a certain amount of vitamins and minerals for its daily functionality. Therefore, various amount of vitamins and minerals should be taken daily. A good example, we should take 1200 mg of calcium, 350-400 mg Magnesium, 148 μg Iodine, 1200 mg Phosphorus, 9-10 mg Zinc (Nielsen, 2010).
Calcium is a vital mineral for the body. Inadequate intake of calcium has been associated by various abnormalities like kidney stones, hypertension, stroke, obesity, insulin resistance, and colorectal cancer (Nordin, 2011). Adequate intake of calcium in the body is associated with increased bone and teeth development.
Calcium concentration in water varies across the globe; these depend on the source of the water. In the United States, the calcium levels are the same in both purified and spring waters. At the same time, the concentration is different in tap water, according to research by Middle Tennessee State University. (n.d.). Given the importance of calcium in the human body, I questioned myself to what extend do we lose minerals, in this case, calcium when boiling tap water.
2 Research question
* To what extend does temperature affect the concentration of calcium ions from tap water, determined by complexometric titration, using Eriochrome Black T indicator?
3 Background information
Tap water can be soft or hard depending on the source, meaning tap water contains some levels of calcium and magnesium ions. To identify the concentration level of calcium and magnesium ions, complex titration is used. Complex titration is a volumetric examination method in where a specific colored compound is used to show the endpoint of the titration. This titration helps in identifying the mixture composition of different metal ions in a solution. In this project, complex titration will be used to assess the quality of tap water. Complex titrations are used when identifying the level of water hardness. Most industries that use water apply complex titration to check their quality of water. Once we establish the presence of calcium ions, we will be able to understand how temperature affects calcium in tap water.
Ethylenediamine tetraacetic acid (EDTA) is a molecule that defines the levels of metal ions in water (Flaschka, 2013). This is based on the principle of the high reactivity nature of EDTA when it reacts with metal ions to form EDTA-metal ion complexes that result in the color changes of the metal indicator (Cranton, 2001). The image below shows the organic composition of EDTA:
3333749773430Figure a: Chemical Structure of EDTA molecule (Cranton, 2001).00Figure a: Chemical Structure of EDTA molecule (Cranton, 2001).
EDTA 4- is a hexadentate ligand, which has lone pairs on all its Oxygen and Nitrogen atoms, and therefore it is able to form coordinate bonds. EDTA solution only forms four coordinate covalent bonds to metal ions when pH is 10. The oxygen and nitrogen atoms in the acid have lone pairs of electrons, which form coordinate bonds when they react with a metal ion, thus creating a complex coordinate compound (Cranton, 2001). The metal complex is quite steady, and the circumstances in which it forms can be controlled, making it the best ligand for a specific metal ion. In this experiment, the endpoint occurs when all the acid reacts with the cation (Slowinki&Wolsey, 2008). The following chemical equations simplify the above statements.
207645090805Ca2+ (aq) + EDTA4- (aq) [Ca-EDTA]2- (aq)
217170083185Mg 2+ (aq) + EDTA4- (aq) [Mg-EDTA]2- (aq)
The above reactions shows how EDTA reacts with calcium and magnesium ions.
According to West 1969, the experiment will require an indicator as both the EDTA and Ca2+ ions are both colorless. Erichrome Black T is the most used indicator. The figure below shows the chemical structure of Erichrome Black T indicator used in the experiment.
41338501215390Figure b: organic structure of ERICHROME BLACK T indicator.00Figure b: organic structure of ERICHROME BLACK T indicator.
This indicator changes from purple to pink when it reacts with calcium ions.
The reverse titration is done using magnesium ions from the magnesium chloride, forming magnesium solution turning the contents pink. The equilibrium position is affected and therefore moving to the right position of the equilibrium. (This is according to a research study conducted by the University of Canterbury, New Zealand.) .The EDTA is known to form a more stable complex than the EBT when it reacts with magnesium ions thus displacing the magnesium ions in the solution (Cranton, 2001). According to Flaschka, 2013, EBT forms a pink color after all the EDTA molecules have reacted, thus indicating the endpoint of the reaction. The equation below explains the back titration reaction in this case.
ErioT + Mg 2+ → ErioT-Mg
4 Hypothesis
Boiling water at higher temperature removes calcium and magnesium ions from the water. It is imperative to understand that boiling water removes water hardness. Thus, rising temperatures of water increases in solubility of the minerals found in water. Therefore, I do presume that the greater the temperature, the lower the calcium levels in the water.
2 Design of investigation
2.1 Variables
Independent variables
The Independent variable in the expriment is temperature. The temperature is varied to identify the content of calcium at each level (McPherson, 2014). The variation of the tmperature will be by the use of a water bath. Each water bath will have a thermometer to measure the temperatures. The temperature is varied at 200, 400,600,800, and 1000.
Dependent variable
The dependent variable in this experiment is the calcium concentrations in the water. The concentration levels of calcium are measured using the back titration method A small sample of tap water is used as the calcium sample, EDTA,EBT and ammonia buffer are mixed to the tap water sample. The solution is then titrated against magnesium chloride solution causing it to turn from a dark blue to a permanent pink color. The calcium content in the water is then determind from the calculations. The answers are the minused from the original calcium content in the water and, thus, the remaining calcium after boiling the water at different temperatures.
Controlled variables
* Concentration of the EDTA- the concentration of EDTA is maintained at 0.005mol/dm-3. This is to ensure that there is no excess EDTA; thus, no magnesium ions that would remain unbonded, making the titration process simple and endpoint easily noticeable.
* The volume of EDTA- the amount of the EDTA is maintained at 20 cm3. This also ensures that there are no extra magnesium ions that would not have bonded with EDTA.
* The concentration of magnesium chloride- Concentration of the magnesium chloride solution is kept at 2.54g
* The volume of EBT is held at one cubic centimeter- too much EBT affects the initial dark color, thus making it difficult to note the slight color changes, consequently affecting the accuracy of the experiment.
* The volume of ammonia buffer solution- more buffer solution is known to dilute the solution hence creating interference to the reaction by making it difficult to note the color changes. The ammonia in the experiment acts as a buffer solution hat helps in maintaining the PH since the reaction between the metal ions and EDTA is dependant on PH.
2.2 Materials and Apparatus
2.2.1 Reagents
* EDTA salt
* Ammonium chloride (solid powder)
* Concentrated ammonia (liquid)
* Magnesium Chloride (solid powder)
* Eriochrome Black T indicator in powder form.
* Absolute ethanol
* One tablet of Calcium and Vitamin D
* Distilled water
2.2.2 Apparatus
* Test tubes
* Clamp stand
* Burette
* 10cm3 graduated pipette
* 20cm3 volumetric pipette
* 500cm3 volumetric flasks with stoppers
* Water bath
* Distilled water
* Timer
* 250cm3 conical flasks
* 50cm3 measuring cylinders
* pipette
* Thermometer
* Spatula
* Top pan scale
* Funnel
* Ruler
Scissors
2.3 Safety and Ethics
Safety precautions
Safety measures

Importance

The ammonia buffer solution must be placed in the emission cupboard.

The ammonia gas produced in the buffering process is corrosive and can be irritating to the skin and eyes.

Lab coats, gloves, and safety goggles to be used all time.

It is crucial to protect the skin and eyes from the reagents like ammonia solutions.

All glassware is to be handled with great care since they are brittle.

Ensuring the glassware does not break to avoid injuries.

Wear heat resistant gloves when handling the water baths

To avoid getting burnt.

Ammonia solutions should be kept away from flames and fires.

The ammonia solution, when heated, produces ammonia gas, which is dangerous to people's health.

Clean up ammonia buffer spills with plenty of water.

Diluting ammonia solution while cleaning up ensure it is well diluted and thus less dangerous.

19050058419Table 1: safety measure and their importance while doing the experiment00Table 1: safety measure and their importance while doing the experiment
Ethical precaution
Ethical precaution

Importance

Ammonia solutions should be discarded into the sink in the fume cupboard and the tap left running to clear the ammonia solution.

Since the ammonia is very toxic, it is not supposed to be poured in the regular sinks that lead to domestic drainage since it can affect the aquatic living things.

Low hazard solutions are just washed away the normal sink, like the EDTA and magnesium chloride.

The chemicals used in this experiment can be washed down the drain since they are considered to be less dangerous to the environment.

238125161290Table 2: E...