Ions in Water. Water Expands when freezing – fish.
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Transcript of Ions in Water. Water Expands when freezing – fish.
Ions in Water
Water
• Expands when freezing – fish
Liquid Water Ice
Water
• Expands when freezing – fish
• Liquid at room temperature – H-bonding
• High specific heat (heat capacity) ↑– Weather
• High heat of vaporization – cooling ↑
• High surface tension – capillary act.↑
Water
• Expands when freezing – fish • Liquid at room temperature – H-bonding• High specific heat (heat capacity) ↑ - weather • High heat of vaporization – cooling ↑• High surface tension – capillary act.↑• An excellent solvent (polar)
– Sometimes good?– Sometimes bad?
Solutions
• Solvent – What things are dissolved in
• Solute – What is dissolved
• Solution – Combination of solvent and solute
• A homogeneous mixture – Dispersed on a molecular scale
• Ionic solute → Electrolyte
• Molecular solute → Non-electrolyte
Solutions
• Solubility– Insoluble– Miscible
• Unsaturated
• Saturated
• Supersaturated
• Solubility of gases in liquids– Soda pop
Dissolving vs. Melting
• To a chemist, a salt is an ionic compound– H+ is not the positive ion (Cation)– OH- is not the negative ion (Anion)
• NaCl melts at 801°C but will dissolve in water at room temperature (20°C)– Means that water really like ions– Cations surrounded by O’s– Anions surrounded by H’s
Precipitate
Salt Solutions
• Conduct electricity – electrolytes
• Lower the melting point of water– As much as 21°C– Salt on roads
Fluoride ion
• Added to drinking water to decrease the number of cavities
• Use is controversial– Aldshymers? – ADHD?
Moles
• Not a furry animal or a turned spy in the CIA.
• Like dozen, gross, ream, etc.
Moles
• Not a furry animal or a turned spy in the CIA.
• Like dozen, gross, ream, etc.
• A mole has 6.02 x 1023 objects in it.– How do you count that many?– Very seldom is Avagadro’s number used– Instead of counting, you weigh a mole
• Using molecular or atomic weights
Concentrations
• Common is percent.• Chemists use molarity, M – moles/liter
– Moles of solute per liter of solution.
• If you need 3 moles of NaCl, how much of 2 M NaCl solution do you want?
• How much solution should you make if you have .5 moles of NaCl and you want 2 M solution?
• The concentration of H3O+ ion in pure water is 1 x 10-7 M.
H25 – C11
• 1, 2, 4 - 6, 9 - 13, 22, 23, 38, 40 - 44, 46, 47, 70, 78