Acids, Bases, and Solutions

Water is polar: δ− oxygens surround Na⁺ and δ+ hydrogens surround Cl⁻, wrapping each ion in a hydration shell that pulls it out of the crystal lattice. No reaction occurs — the ions are just separated and surrounded.

Polar/ionic solutes dissolve in polar solvents (salt or sugar in water), and nonpolar solutes dissolve in nonpolar solvents (capsaicin or vitamins A/D/E/K in oil). That's why you bloom chili in oil, not water.

Each soap molecule has a nonpolar tail that buries itself in grease and a charged head that water grabs, forming micelles — grease-filled spheres that rinse away.

Moles of solute per litre of solution. Seawater ≈ 0.6 M NaCl, blood ≈ 0.15 M total salts, stomach acid ≈ 0.1 M H⁺.

Heat usually increases solubility of solids (sugar in hot syrup) but decreases solubility of gases — so warm soda goes flat faster and warm rivers hold less dissolved oxygen.

Kw = [H₃O⁺][OH⁻] = 1×10⁻¹⁴ at 25 °C. Because the product is fixed, raising hydronium must lower hydroxide — the hinge of all acid-base chemistry.

An acid is a proton (H⁺) donor; a base is a proton acceptor.

A strong acid (HCl) donates its proton completely; a weak acid (acetic acid, Ka = 1.8×10⁻⁵) only partly dissociates. Weak ≠ dilute: glacial acetic acid is concentrated but still weak.

pH = −log₁₀[H₃O⁺]. Each unit is a factor of ten, so lemon juice at pH 2 is 1000× more acidic than coffee at pH 5.

It holds the maximum solute it can at that temperature — about 360 g of NaCl per litre of water at 25 °C — and no more will dissolve.