An environmental chemist is evaluating the fate of four organic substances released into a freshwater lake at pH 7 and 25 °C:
1. Ethane (C₂H₆)
2. Ethanol (C₂H₅OH)
3. Stearic acid (C₁₇H₃₅COOH)
4. Sodium stearate (C₁₇H₃₅COONa)
All four substances are initially present as pure materials apart from the lake water.
(a) Rank the substances from highest to lowest equilibrium concentration of dissolved species in the lake water.
(b) Provide a comprehensive explanation for your ranking that addresses polarity, ionization state, hydrophobic interactions, and any amphiphilic behavior relevant to dissolution.
(c) Predict qualitatively how lowering the lake water pH to 3 would alter the solubility of stearic acid and sodium stearate, and justify your prediction based on speciation and intermolecular forces.