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