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Ions in Water

Ions in Water

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Ions in Water

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  1. Ions in Water

  2. Water • Expands when freezing – fish

  3. Liquid Water Ice

  4. 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.↑

  5. 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?

  6. 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

  7. Solutions • Solubility • Insoluble • Miscible • Unsaturated • Saturated • Supersaturated • Solubility of gases in liquids • Soda pop

  8. 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

  9. Precipitate

  10. Salt Solutions • Conduct electricity – electrolytes • Lower the melting point of water • As much as 21°C • Salt on roads

  11. Fluoride ion • Added to drinking water to decrease the number of cavities • Use is controversial • Aldshymers? • ADHD?

  12. Moles • Not a furry animal or a turned spy in the CIA. • Like dozen, gross, ream, etc.

  13. 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

  14. 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.

  15. H25 – C11 • 1, 2, 4 - 6, 9 - 13, 22, 23, 38, 40 - 44, 46, 47, 70, 78