Discuss the processes that are used in a water treatment plant to produce water that is suitable for drinking.
Fluoridation of water supplies has been a topic of debate for many years. What effect does fluoridation have on teeth?
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I'm relating to the movie our class recently watched. The fluoride ion is a negative charge and so therefore the ion should be attracted to the positive end of the water molecule. If this is true, a book i read stated that the safe amount of fluoride in water is one part per million. How is this possible? Does this mean that out of one million water molecules a fluoride ion is attached onto a water molecule via hydrogen bonding?
Fluoride will be a hydrated ion just like chloride on p 296 of your text book. This is not hydrogen bonding - rather a strong attraction between the water dipole (hydrogen end) and the ion. ppm is a mass mass comparisonand not a particle particle comparison. It means 1 mg of F- is dissolved in every litre of water.
Hey you know the thing we did in class on the 22nd about saturated and unsturated ions. F- in water supplies would be unsaturated because the is more solvent than the solute. Is it possible to find how many H2O molecules are attached? to the F- ion? Do we need to incorperate the toxicity of F- in the essay.
Bobby
When we discuss how water is treated i talk about how chemicals alum and lime are used to help settle the particles. is this definiton of alum correct:
A combination of an alikali metal and a trivalent metal simplified in this formula:alkali metal 2(subspt) SO 4(subspt)·(trivalent metal 2 (subspt)(SO 4 (subspt))3(subspt)·24H2(subspt) O
Dear Bobby!
I don't really think there is an answer to the number of water molecules. FLuouidated water would be very dilute and therefore there would be many water molecules separating fluoride ions from other ions. The opponents of fluoridation often refer to fluoride toxicity as an argument against fluoridation. Use the evidence to decide who is in the right and argue your point based on the supporting evidence. With this in mind you will have to evaluate the toxicity argument.
The definition of alum seems correct but I thought the trivalent metal was Al is this not always the case? (I am not doing the research you see. You really do need to explain how they work rather than just what they do.
Hey,
This is concerning the reaction with alum and raw water. My tutor said that the reaction may not be a chemical reaction but a physical reaction. Should i still be looking at books + net to find what reactions occur. From this site is states, " alum attracts and stick to many of the suspended water particles. Many of coagulant's cations, under appropriate pH and other conditions, react with water to form insoluble hydroxides which join together to form larger settleable particles or physically traps small particles into the larger floc."
Is this a physical reaction that a chemical one?
A chemical reaction produces a new substance. Making particles stick together is not a chemical reactiomn if they are not forging new ionic/covalent bonds. Describing the chemistry is not just about reactions but about a particle level perspective. You will need to examine precipitation according to your source about hydroxide.
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