Bozzhigitova Dinara ENVIRONMENTAL CHEMISTRY LABS

T8714SN Report

Marjatta Lehesvaara Date: 06.05.15

1 Introduction

The aim of these laboratory works was to find out and measure chemical properties such as pH, conductivity, COD, total hardness, dissolved oxygen, phosphate concentration in different samples of water. `

2. Laboratory works

2.1 Treating of natural water

In chemistry the are a few methods how to treat water. On this laboratory work we used method called flocculation. Flocculation  in physical chemistry, separation of solid particles from a liquid to form loose aggregations or soft flakes. These flocculates are easily disrupted, being held together only by a force analogous to the surface tension of a liquid. In industrial processes, flocculation may be a desired or an undesirable phenomenon, and various methods may be used to cause or eliminate flocculates.[ CITATION htt151 \l 1033 ]

During treating of natural water following equipment was used: measuring cylinder with the volume of 1000 ml, magnetic bar, magnetic stirrer, water sample and FeSO₄ solution of 1% concentration.

Firstly, our group measured 500 ml of water in a measuring cylinder and added 10 ml of FeSO₄ solution. Then, we mixed obtained solution about one minute at full speed using magnetic bar and magnetic stirrer. The next step of treating natural water was to change speed until solution will be mixed at the top also and let it mixed for a 10 minutes. After this, we let the water settle down. Treating of natural water was finished and we could take water sample for the following laboratory works. Taking of water sample must be done very carefully so that it will not mixed with a precipitate.

2.1 pH

Firstly, our group measured pH of tap, natural and treated natural waters. pH is a scale measures how acidic or basic a substance is. The pH scale ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic. Determination of pH is one of the most important analysis of water. It can be measured instrumentally. For this aim following equipment was required: pH-meter, pH-electrode, 3 beakers, byrette, magnetic stirrer, buffer solutions (pH 4, pH 7 in the temperature 18-22 C°)

For the accuracy of measurements we calibrated the ph-meter by two buffer solutions. Then, our group filled three beakers by 50 ml of tap, natural and treated natural waters. For determination of pH we dipped an electrode of pH-meter into the solution and read the results. In the end of this part of laboratory work we get following results

Analysis	Tap water	Natural water	Treated natural water
pH	7,55	6,15	3

According the results we can say that tap water has weak base environment, natural water has weak acid environment.

2.2 Conductivity

The conductivity of a solution is an expression of the capacity of that solution to conduct electric current.[ CITATION Pet13 \l 1033 ] It depends on concentration, temperature, structure of the solution

For determination of conductivity in tap, natural and treated natural waters following equipment were used: conductivity meter with conductivity probe, water samples, beakers, 0,1 mol/l KCl solution.

Firstly, our group calibrated conductivity meter by 0,1 mol/l KCl solution. Then, we measured the conductivity of each samples, which were used in determination of pH level and waited for stabilization of the results.

Analyse	Tap water	Natural water	Treated natural water
Conductivity (mS/cm)	0,205	0,075	0,505

The conductivity of tap water is higher than conductivity of natural water. It can be caused by high concentration of NaCl, MgCl, CaCl in tap water. Salts has ionic structure, which can conduct electricity.