Analytical Chemistry Lecture 1 PDF

1  1st Lecture 2  Properties of Water It is clear, transparent, tasteless and odorless fluid. It is colorless in small quantities, pale blue through deep column. It freezes at 0°C and boils at l00°C under normal pressure. It has greatest density at 4°C. It is a good solvent as d...

1  1st Lecture 2  Properties of Water It is clear, transparent, tasteless and odorless fluid. It is colorless in small quantities, pale blue through deep column. It freezes at 0°C and boils at l00°C under normal pressure. It has greatest density at 4°C. It is a good solvent as dissolves almost all substances( solid, liquid or gases). 3  Classification of water Sources According to Purity uses 4  According to purity 3- Contaminated 1-Pure 2-Polluted water water Free from chemical This type of water It contains poisons, infectious undergo changes in animal and diseases, human its physical human wastes, and animal wastes characters which may carry infectious hygienically pure diseases, as well and safe for color, odour, as chemical human taste, turbidity. poisons e.g consumption. pb2+, As5+ 5  According to Sources Rain water 1 2 Surface water Under ground water 3 6 ØIt is the purest type of water and similar to distilled water ØIt may contain some dissolved gases, e.g O2, NH3, N2, CO2. The presence of CO2 and nitrous oxides, causes acidity to rain water but it can be removed by boiling. ØRain water may contain inorganic constituents e.g NaCl due to spray lifted from oceans into atmosphere due to wind action. ØH2SO4 may be present due to oxidation of SO2 produced from coke combustion. air H2O SO2 ¾¾® SO3 ¾¾® H2SO4 ØIt is a soft water (free from Ca2+ & Mg2+). ØIt 7 contains some micro-organisms floating in the air. ØIncluding rivers, canals, lakes & ponds ØIt is exposed to contamination by dust, soil, sewage & wastes. ØIt contains dissolved solids from the soil e.g Ca2+ and Mg2+. In relatively small concentration, therefore it is described soft water. ØIt contains CO2 and organic acids (from decaying roots), and large number 8 of pathogenic bacteria.  Some of surface water soaks into the ground to form underground water. Present as springs and wells. It differs from surface water in that: 1-it is much pure and less polluted due to filtration and oxidation of microorganisms during percolation through the soil. 2- It is harder than surface water due to high amount of dissolved Ca2+ and Mg2+. 3- Its acidity due to CO2 is more than that of surface water (CO2 resulting by organic decomposition). Some underground water contains sulphur which 9 is of medical importance.  According to Uses It must be It must be It must be clear, soft to pure free It must be from colorless, avoid 4- Pharmaceutical neutral as chemical odourless, 3- Industrial acids or damage of poisons and tasteless, alkalis fibers when 2-Irrigation free from infectious would spoil used for 1-Potable chemical diseases. the soil. textile Also it must poisons and infectious industry. be pyrogen diseases. free It must be soft as it is used for domestic purposes. 10  Sampling of water Sample taken must be representative, Therefore, it is recommended to collect and store sample in bottle made of inert material e.g resistant boro-silicate glass, hard rubber,…etc. 11  Sampling of water For taking a representative sample: Before collecting samples from distribution systems, the line should be flushed for a sufficient period. - Samples from wells, should be collected only after the well has been pumped. - Samples from a river or stream, take sample from top to bottom in the middle of stream. 12