Wed, Oct 31

A. Phosphoric acid - recall weak

- in Cokes and foods
- phosphates are big-time fertilizer components
- phosphate linkages are used in muscle energy storage

Prep of pure phosphoric acid (for foods)

    = start with calcium phosphate, go to elemental P, then convert to acid

          calcium phosphate to elemental P - uses SiO₂ and C - we can understand why
          elemental P = white (P₄) and red P  - we can understand why
          P₄ to acid - first burn, then add water - we can understand why

Heating phosphoric acid gives di, tri, etc polyphosphates - we can figure out these formulas

    Detergent use - why there is an environmental concern (not = people getting too clean)

B. Sulfur and Acid Rain

We'll discuss the preparation of sulfuric acid and why it is the #1 manufactured chemical in the world. 

We do the structure of elemental sulfur.

And we'll do the reactions related to acid rain:

Acid Rain is mostly from coal burning, not auto
               S + O₂ = SO₂  SO₂ + O₂ = SO₃   SO₃ + H₂O = H₂SO₄
              1 mole S (32 g) gives 1 mole acid (96 g), so 1 ton S gives 3 tons acid

Damage to statues (removes noses and ears):  H₂SO₄ + CaCO₃ (marble) = CaSO₄ (washes off) + CO₂ + H₂O
 

Controls: scrubbers:  SO₂ + CaO = CaSO₃ or SO₃ + CaO = CaSO₄
                   (CaO from heating limestone CaCO₃ = CaO + CO₂)