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minor address change

2008 Chemistry Year 11 Term 2 SA S

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12.30-2.30pm

Fresh water - less than 1,000 ppm Slightly saline water - From 1,000 ppm to 3,000 ppm Moderately saline water - From 3,000 ppm to 10,000 ppm Highly saline water - From 10,000 ppm to 35,000 ppm

ppm = parts per million this means mg per L, for example if a solution has a concentration = 1g per L this is the same as 1000ppm

Wed 11th June

Part A - Stimulus: Research and Data collected for SA. 1 page typed text for introduction I page for materials, methods and results.

Bring along a calculator, your research (1 page) and a (1 page) partly completed lab report (this can include all the procedure and your raw titration results.

Water quality is highly variable, and for any task an appropriate grade of water must be chosen. For example, tap water is fine for washing dishes. It is not recommended for making solutions because the quality of such water is unknown. Tap water typically contains sediments (suspended particles), metal and other ions, deliberately added chemicals such as chlorine or fluoride, and/or traces of organic solvents. Although tap water is generally safe for drinking and other personal uses, materials in tap water can be toxic to some cells or may interfere with assays or biochemical reactions. It is recommended that glassware that has been washed and rinsed in tap water be thoroughly rinsed with a higher quality water. Distilled water, obtained from the condensation of steam, is of better quality because distillation eliminates all of the sediment and most of the inorganic solutes. Organic contaminants and some of the inorganic contaminants remain. Deionized water is produced by running tap water through a resin cartridge or series of them. A home deionizing system might simply replace divalent cations with sodium ions, producing what is commonly known as “soft” water. Laboratory deionized water is usually treated so as to remove both cations and anions, which are exchanged for hydrogen and hydroxyl ions respectively. Deionized water is often of better quality than distilled water although on the downside, the resins used in the cartridges may release organic contaminants into the water. The highest grade of water is called 18 megohm water. Eighteen megohms is 18 million ohms, which are units representing resistance to the flow of electricity. Eighteen meghoms is more than a million times the electrical resistance of a typical household electric circuit. Very pure water does not conduct electricity well compared with contaminated water because it contains no inorganic ions with which to carry electric current. Eighteen megohm water is usually produced in multiple steps, including reverse osmosis and the passage of product through ion exchange resins, activated carbon beds and filters. Pure water is somewhat acidic, with pH close to 5. It is also what we call an aggressive reagent, meaning that it will leech ions from plastic or glass containers. It does so because of the polar nature of water molecules. Ions dissolve most readily in 18 megohm water because the system (water plus dissolved ions) is more stable than when pure water is separated from soluble materials. Because very pure water accumulates contaminants during storage, it should be freshly prepared. The use of plastic tubing, funnels, and especially metal containers, should be avoided.

http://www.ruf.rice.edu/~bioslabs/methods/solutions/water.html

http://www.rpi.edu/dept/chem-eng/Biotech-Environ/Adsorb/adsorb.htmcarbon adsorptionhttp://www.cee.vt.edu/ewr/environmental/teach/wtprimer/carbon/sketcarb.html#Adsorp

http://www.lenntech.com/deionised-demineralised-water.htm

WOW useful!

http://www.culliganmiami.com/pf5.html About deionizer resins

http://www.youtube.com/watch?v=UHYWIM8AbPE

watch at home!

http://www.geocities.com/setseng2004/ConductivityandSalinityofAqueousSolution.pdf

testing water quality by conductivity

http://www.google.com.au/search?hl=en&q=recyling+water+Queensland&meta=cr%3DcountryAU

http://www.google.com.au/search?hl=en&q=desalination+Queensland&meta=cr%3DcountryAU

Desalination + recycling in QLD

VIDEO

Salt titration

AgNO3 + NaCl ---------> AgCl + NaNO3

2AgNO3 + K2CrO4 --------> 2KNO3 + Ag2CrO4(s)

When all the salt has been used up, AgCl can no longer form

The first drop of excess AgNO3 reacts with the chromate solution and it forms the red ppt

K2CrO4 acts as the indicator

AgNO3 + NaCl ---------> AgCl + NaNO3

A typical calculation

1 1:

25.00mL of C0.1M / 26.07mL

= 2.607 x 10-3 mole 25.00mL of salt contains = 2.607 x 10-3 mole

C = 0.1042M

M NaCl = 58.5g

mass of NaCl per L?

0.1042 x 58.5g = 6.0957g

or 6096mg per L this solution should fit into the moderate range

Please collaborate (share ideas) and links etcPlease test yourself by answering the SA at home the written section is two hours! Check your calculation, and buy new calculator batteries!