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 = $\frac{mg}{L}$ (for dilute aqueous). Dilution: M1V1 = M2V2 (moles conserved). Mixing: $M_{final}$ = $\frac{M1V1 + M2V2}{(V1 + V2)}$ 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 = 1000$\frac{M}{1000d - M x M_solute}$. Molarity from density and mass%: M = 10 x d x w% / $M_{solute}$.