CHEMCOM Review of Water Parts C

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CHEMCOMReview of Water Parts C D,
Understanding Possible Causes of the fish Kill

• These five concepts will be on tomorrows quiz

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1. SOLUBILITY

• Be able to interpret a solubility graph know
  where saturated, unsaturated and supersaturated
  are on graphs like the one on pg 46.
• Distinguish between solute and solvent.
• Calculate by mass for a solution such as one
  containing 50.0 g salt in 100.0 g water.
• Know that gases dissolve better in cold water
  than in warm water

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2. LIKE DISSOLVES LIKE

• Be able to recognize polar solutes/solvents vs..
  nonpolar just by looking at the formula (water,
  ammonia and anything with an OH group is polar)
• Know that polar solvents dissolve polar solutes
  (nonpolar solvents dissolve nonpolar solutes).
  See demo lab on this.

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3. Toxic Metal Ions

• Reread pg 54 and 55 regarding the dangers of lead
  and mercury ions in drinking water.
• Know which of these ions is a local problem for
  people living in Los Gatos and Almaden Valley.
  Know which was used in paints, felt hats,
  gasoline.

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4. pH

• pH greater than 7 is basic
• pH 7 is neutral
• pH below 7 is acidic
• The pH scale goes by tens so pH 6 is ten times
  more acidic than pH 7 and pH 5 is a hundred times
  more acidic than pH 7.
• Foods tend to be neutral or acidic. Cleaning
  supplies and soap are often basic. (recall
  Homelab on pH)

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Be able to recognize acids and bases from their
formulas

• Acids start with H, for example.
• HCl hydrochloric acid
• H2SO4 sulfuric acid
• And they transfer H ions (protons) to H2O
• Bases end in OH and they release OH- ions
• NaOH sodium hydroxide (lye)
• Ca(OH)2 calcium hydroxide

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5. HARD WATER

• Know that hard water is healthy, but creates soap
  scum and boiler scale.
• Hardness in water is caused mostly by calcium
  ions, Ca2
• Water can be softened by using an ion exchange
  resin (water softener) which replaces calcium
  ions with sodium ions.
• A chelate, like Calgon, also softens water but it
  interferes with the calcium ions rather than
  removing them.