Molarity (M) = mol solute / L solution. Normality (N) = eq solute / L = M x n-factor. Molality (m) = mol solute / kg solvent. Mole fraction (x) = mol / total mol. ppm = mg/L (for dilute aqueous). Dilution: M1V1 = M2V2 (moles conserved). Mixing: M_final = (M1V1 + M2V2)/(V1 + V2) for same solute. For acid-base mixing: calculate meq acid and meq base, subtract to find excess, divide by total volume. Interconversion: Molarity to molality: m = 1000M/(1000d - M x M_solute). Molarity from density and mass%: M = 10 x d x w% / M_solute.