$word_{count}$: 210

Equivalent weight = molar mass / n-factor. n-factor depends on the reaction type. Acids: n = number of H+ donated (HCl:1, H2SO4:2, H3PO4:1,2,or 3 depending on reaction). Bases: n = number of OH- donated (NaOH:1, Ca(OH)2:2). Oxidising agents: n = total decrease in oxidation state per formula unit (KMnO4 acidic: $Mn^{7+}$ to $Mn^{2+}$, n=5; K2Cr2O7: 2Cr, each +6 to +3, n=6). Reducing agents: n = total increase in oxidation state. Salts: n = total positive charge per formula unit (NaCl:1, BaCl2:2). Normality N = M x n-factor = $\frac{equivalents}{L}$. Number of equivalents = $\frac{mass}{eq}$.wt = moles x n-factor. Law of equivalence: at the stoichiometric point, equivalents of one reactant = equivalents of the other. N1V1 = N2V2 or M1V1n1 = M2V2n2. This is more general than mole-ratio calculations and avoids the need to write balanced equations for simple neutralisation and redox titrations. Key trap: n-factor of H3PO4 depends on which product forms (NaH2PO4: n=1, Na2HPO4: n=2, Na3PO4: n=3).