Does Tap Water Contain Magnesium and Calcium?

The quantity of minerals present affects the quality of the water. Since they are present in higher concentrations than other components, calcium and magnesium are employed to test for minerals that make water hard. Every cleaning task, including bathing, dishwashing, shaving, and laundry, is hampered by the hard water. Hard water-washed clothing may seem discolored and feel rough or scratchy, and when dry, hard water can leave stains on dishes and glasses. Additionally, hair cleaned in harsh water may appear dull and sticky. The cost of dealing with hard water issues at home is high because it necessitates using more detergent. Moreover, water hardness can reduce the flow of water in the pipe due to the formation of deposits. Due to the problems associated with hard water, it is significant to know the concentration of calcium and magnesium. The experiment below will illustrate how to test the quality of water at home.

Relevance of Question

The result and question of the experiment could be relevant to every person who uses water tap and faces various predicaments associated with water hardness. Furthermore, the experiment is more useful to people who are planning to start water projects and various industries involved in food production. Additionally, the result will be relevant to industries that produce mineral water and people who analyze the safety of water consumed by the public.

Literature Review

The obvious application of the evaluation of magnesium and calcium in water is to test for hard water. The water hardness refers to the sum concentration of alkaline metal ions and since the concentrations of magnesium and calcium are much higher than those other earth ions, hardness is equated to the magnesium and calcium ions (Silva, Nóbrega, Jones, & Donati, 2014). Hard water causes insoluble compounds in boilers, heaters, and pipes as well as consuming soap that could have been utilized for cleaning. According to Silva et al, there have been no prove that taking hard water is dangerous although drinking deionized water is regarded unhealthy since it does not have normal electrolyte balance. Water hardness can be evaluated by various methods such as EDTA titration and atomic emission and absorption spectrophotometer.

The atomic emission spectroscopy is the convenient technique for the recognition of alkali metals since they are excited in flames. When the magnesium and calcium atoms are excited at the low flame temperatures, they release visible radiation that reads in the spectrometer. According to Fortunato et al. (2015), the atomic emission spectroscopy is founded on the evaluation of the wavelength of photons that are discharged by the molecules and atoms as they move from the high energy to low energy state. The characteristics of wavelengths are emitted by every element and depends on the electronic structure (Fortunato, Bechlin, Neto, Donati, & Jones, 2015). The sample to be analyzed is brought into the flame in the solution or gas form, and the liberated atoms are formed when the flame evaporates the solution and damages the links. Moreover, the heat converts the atoms into electrical particles that produce light when getting back the lower electronic state. Due to the emission of beam at the wavelength of each element, the numbers of atoms are detected by the spectrometer (Fortunato et al., 2015).

Experimental Design Steps

The water sample was corrected from the home tap and stored in the beaker. Two beakers of the capacity of 200ml were filled with the tap water for the experiment.

The stock solution will be made for both magnesium and calcium as follows:

Magnesium Stock Solution

Accurately weigh 0.001 gram of dry magnesium oxide and put into the 1000ml volumetric flask. Rinse the volumetric flask with deionized water. Later dissolve a few ml of 6M hydrochloric acid and then adulterate to the spot with deionized water while mixing carefully.

Calcium Stock Solution

Weigh 0.252g of dry calcium carbonate and wash it into the 100 ml flask with little amount of deionized water. Secondly, add few amounts of 6M hydrochloric acid and then fill to the top using water water and shake carefully.

Reasoning

The stock solution is the mixture of the known concentration that will be used to determine the number of ions in the water sample. The preparation of the stock solution is based on the molecular mass of the element and is used to save the preparation time, reduce storage space, conserve materials and improve the accuracy by functioning with lower concentration solutions. Besides, the stock solution will be used to obtain the standards for the construction of calibration curve after which the sample results will be equated to determine the actual concentration. The concentration of the standard solution will be identified and the wavelength emission recorded. Besides, the concentration and absorbance will be used to draw the calibration curve. The amount of magnesium and calcium in water will be determined by plotting the absorbance on the calibration curve.

Sequence of Events

Measurement of Calcium

In five dry beakers, 250 ml deionized water was added using the graduated cylinder to measure the volume carefully. With the use of 500 microliter automatic pipettor, 2.0, 1.5, 0.00, 0.5 and 1.0 ml of calcium stock mixture was added to every beaker respectively and mixed thoroughly. Moreover, the concentration of calcium in the standards was calculated. The flame atomic spectrophotometer was set according to the operation instructions in the manual. The full sets of standards of calcium were measured and the absorbance recorded before switching to magnesium. The unknown water sample was also measured, and in case the absorbance was too large, it was diluted.

Measurement of Magnesium

After completing the calcium assessment, the spectrophotometer was cleansed using the deionized water until there was no reading and then switched to measure magnesium element. To prepare the standard solution, five beakers were filled with 250 ml of deionized water. Later, 0.5, 0.0, 2.0, 1.0 and 1.5 ml of the magnesium stock mixture were put to beakers respectively. The element selection of the machine has to be changed so that to measure magnesium. The standards and the sample have to be measured and the highest absorbance recorded.

Tools and Technologies

• 100 ml volumetric flask

• Ten 250 ml beakers

• Two water samples in the 100ml beakers

• 500 micro liter automatic pipettor

• 1000 ml volumetric flask

• AAS spectrophotometer

Variables

Independent variable: The concentration of both the standard solutions which will be used to construct the calibration curve in the X-axis.

Dependent variables: The absorbance reading in the spectrometer of standard solutions. The absorbance will be used to construct the calibration curve in the Y-axis.

Controlled variables: The amount of water used as the sample will be the controlled variables. The volume of water will be reduced in case the absorbance exceeds the normal readings.

Threat Reduction to Internal Validity

By accurately measuring the required volumes and mass for the preparation of stock solution and dilutions, the experiment assures that correct concentration will be obtained. Furthermore, the machine will be changed to measure each element so that to avoid contradicting readings. The standard solutions provide the right absorbance that each element can indicate. To reduce threat on the dependent variables, the sucking tube of the spectroscopy will be rinsed with distilled water until there is zero reading after and before assessing different solutions and samples.

Hypothesis

The hypothesis of the test is that calcium and magnesium presence in water are the major cause of water hardiness. The hypothesis was founded on the statement of Fortunato et al that magnesium and calcium ions are the majority in water hence appropriate to determine the hardiness.

Data Collection Process

As projected, each standard solution had different concentrations of every element. The stock solution helped to provided standards that illustrated varying reading in the machine. Moreover, each sample showed a specific reading. The magnesium stock solution in the five tubes was added with the interval of 0.5 ml starting from zero to 2.0 ml where the concentration (mmol/l) had the interval of 0.2 starting from zero to 0.8. Also, the amount of calcium stock solution added in the five tubes for the preparation of standard solution had an interval of 0.5 ml starting from zero to 2ml and the concentration had an interval of 0.3 ranging from 0 to1.2 mmol/l.

Standard (Ml)

Concentration (mmol/L)

Magnesium

Calcium

Magnesium

Calcium

0.0

0.0

0

0

0.5

0.5

0.2

0.3

1.0

1.0

0.4

0.6

1.5

1.5

0.6

0.9

2.0

2.0

0.8

1.2

Figure1: Amount of stock solution and concentration of standard solution

Appropriate Methods

Since each standard has a particular concentration of calcium and magnesium ions, the amount in the water sample will be identified by plotting the reading on the calibration graph. Determining the concentration in a given volume can be used to determine the hardness of the tap water.

Results

Figure 2: Magnesium Calibration Curve (Concentration against Absorbance)

Figure 3: Calcium Calibration Curve (Concentration against Absorbance)

As the above graphs illustrate, the water sample had different concentration of calcium and magnesium. The concentration of magnesium was 0.6mm/L while that of calcium was 0.9 mm/L. The levels indicate that the hardness of the sample water is moderate hence can cause fewer problems with washing.

Conclusion

Confirmation of Hypothesis

The results confirm the hypothesis since the absorbance indicated that there were magnesium and calcium elements in the water. The two ions represent water hardness since they are in higher concentration than other metals.

Experimental Design as Key Factor

The use of atomic emission spectrometer is crucial in testing the presence of magnesium and calcium in different water sources because each element gets excited differently thus indicate distinct wavelength. The experiment must be able to rely on the correct stock solution and standards.

Replication

The replication of the experiment needs the correct calculation of the stock and standard solutions. The right measurements must be measured to have correct concentrations. Moreover, the right weights and addition of the hydrochloric acid must be observed.

Evaluation of Validity

The validity of the experiment can be confirmed by different analytical methods that are used to analyze the hardness of water. Furthermore, the test can be replicated to verify if the results are valid with the use of similar samples. The replication should be done using the similar samples of water tap. Moreover, the same machine used to show absorbance should be the same and standard solutions have to be of alike concentrations.

References

Fortunato, F. M., Bechlin, M. A., Neto, J. A. G., Donati, G. L., & Jones, B. T. (2015). Internal standard addition calibration: Determination of calcium and magnesium by atomic absorption spectrometry. Microchemical Journal, 122, 63–69.

Silva, S. G., Nóbrega, J. A., Jones, B. T., & Donati, G. L. (2014). Evaluation of Mg and Mn determination in water and plants using continuum source tungsten coil atomic fluorescence spectrometry. Microchemical Journal, 117, 250–254.