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19 Water

Chapter 19 Chemistry Live

TermDefinition
Hard Water water that will not easily form a lather with soap, caused by the presence of Ca2+ & Mg 2+ ions
Treatment - Screening passing the water through a wire mesh to remove floating debris
Treatment - Flocculation Aluminium sulfate is added and suspended solid to stick together to form larger particles
Treatment - Settlement water flows from the bottom of large tanks and very slowly rises to the top; as a result the 90% of the particles are removed.
Treatment - Filtration The water is passed through large beds of sand and gravel, this removes remaining solids. the water is now clear
Treatment - Chlorination Chlorine is added to water to sterilise it, to kill any harmful microorganisms (0.5ppm)
Treatment - Flourination Sodium flouride is added to prevent tooth decay
Treatment - pH adjustment Calcium Hydroxide/ Sulfuric acid are added if needed to maintain a pH of 7-9
Biochemical Oxygen Demand The amount of dissolved oxeygen consumed by a biological action when a sample of water is kept at 20 degrees celsius in the dark for 5 days
Eutrophication The enrichment of water with nutrients, which leads to excessive growth of algae & other plants.
Temporary Hardness is the hardness that can be removed by boiling the water caused by Ca(HCO3)2 ie Ca2+ ions
Permanent Hardness is hardness which cannot be removed by boiling the water, caused by CaSO4 or MgSO4.
Limestone CaCO3 insoluble Calcium Carbonate
Limestone + Carbonic acid CaCO3 + H2CO3 = Calcium Hydrogen carbonate Ca(HCO3)2 (soluble)
Ca(HCO3)2 + heat = CaCO3 + CO2 + H2O
Distillation Boiling water & condensing vapour. All dissolved solids & liquids are removed from the water by this method.
Na2CO3.10H2O Used to remove hardness by reacting the Ca ions with the CO3 and forming insoluble CaCO3.
Ion-exchange resin exchange or 'swap' ions that cause hardness Ca2+ or Mg2+ with ions that do not cause hardness Na+
Cation A positive ion
Distilled water purest form of water as all dissolved,suspended solids as well as gases have been removed from the water
Deionised water only the ions have been removed may still contain non-ionic dissolved solids or gases.
Total Hardness Calcium hardness + Magnesium hardness
Complexometric titration A titraion involving the formation of a complex between the metal ions and a reagent such as edta. The end point is determined by a sharp decrease in the concentration of free metal ions
Buffer solution maintains a constant pH
Flocculating agent A chemical added to water to coagulate suspended particles and thus help sedimentation to take place.
Clacium Hydroxide Ca(OH)2 to raise the pH
Sulphuric acid H2SO4 to lower the pH
Fluoridation compounds Hexaflurosilicic acid or Sodium Fluoride
Oxygen solubility is temperature dependent as oxygen is a non-polar molecule
Winkler Method Titration with sodium thiosulphate carried out to determine the dissolved oxygen content of water
EDTA EthyleneDiamineTetraAcetic Acid
Eirochrome Black T Wine-red to Blue
Winkler sample water sample with manganese sulphate, alkaline potassium iodide and conc'd sulphuric acid added
Starch Indicator added when solution is straw yellow it turns blue/black and titrate until colourless
No dissolved oxygen present If White Percipaitate does not turn brown
Primary Treatment a mechanical process in which large solids are removed by settlement (sedimentation)
Secondary treatment a biological oxidation process in which the levels of suspended & dissolved organic materials are reduced i.e. The sewage is decomposed by means of bacteria which use the nutrients from the slurry & the oxygen from the air to break down the sewage.
Teritary Treatment a process involving the removal of phosphorus compounds by percipitation & the removal of nitrates by biological & ion-exchange methods
Atomic absorption spectrometry Measures the concentration of heavy metals in water
Percipitation method of removal of heavy metals in water eg Lead ions are reacted with dilute Hydrochloric acid to produce Lead chloride percipitate
Principle of colorimetry Is that the amount of absorbance of light by a coloured solution is proportional to the concentrationof the solution
Created by: Ms O'Farrell
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