Solutions, Acids, and Bases
Solutions, Acids, and Bases
This domain tests concentration, dilution, solubility, electrolytes, colligative properties, pH, neutralization, buffers, and titration. Expect both conceptual comparisons and quantitative pH or dilution calculations.
Solutions
- Molarity = moles solute / liters solution. Dilution: M1V1 = M2V2.
- Strong electrolytes dissociate completely; weak electrolytes partially; nonelectrolytes do not.
- Colligative properties depend on particle count: ionic compounds produce more particles and larger effects.
- Solubility depends on temperature, pressure for gases, and solute-solvent interactions.
Acids and bases
- Arrhenius acids produce H+ in water; Bronsted-Lowry acids donate protons; Lewis acids accept electron pairs.
- Strong acids and bases ionize completely; weak ones reach equilibrium with Ka or Kb.
- pH = -log[H3O+], pOH = -log[OH-], and pH + pOH = 14.00 at 25 degrees Celsius.
- Buffers resist pH change by neutralizing added acid or base; capacity depends on component concentrations.
Worked example
A 0.010 M Ba(OH)2 solution is a strong base that gives two OH- ions per formula unit, so [OH-] = 0.020 M. pOH = -log(0.020) = 1.70; pH = 14.00 - 1.70 = 12.30. Do not use 0.010 M directly for pOH, and do not assume the solution is neutral.
Traps
Using solution volume instead of solvent volume for molarity; forgetting the stoichiometric number of ions; confusing strong with concentrated; using pH + pOH = 14 at temperatures other than 25 degrees Celsius; and ignoring the 1:1 mole ratio in a titration without checking the equation.