89.2 Reaction rate and rate equation (4)Rate equation In 1895, Noyes defined a, Bas the partial H 2+C2=2 HCI order of the reaction with respect to A or B r=k[H,1[CLI respectively, and the sum of the partial order n=a+B+r+. the overall order of the 2SO2+O2→>2SO3 reaction, or more simply, the reaction order. dso 2kISO,[so 2 a, B % etc, different from the Rate law must be determined from stoichiometric coefficient, may be integers, measurements of reaction rate and cannot decimals, of plus or minus values be deduced from the reaction stoichiometry1 0.5 2 2 r k  [H ] [Cl ] (4) Rate equation §9.2 Reaction rate and rate equation 2SO2 + O2  2SO3 1 3 2 2 3 [SO ] 2 [SO ][SO ] d r k dt    , , , etc., different from the stoichiometric coefficient, may be integers, decimals, of plus or minus values. Rate law must be determined from measurements of reaction rate and cannot be deduced from the reaction stoichiometry. H2 + Cl2 = 2 HCl In 1895, Noyes defined ,  as the partial order of the reaction with respect to A or B, respectively, and the sum of the partial order n =  +  +  +… the overall order of the reaction, or more simply, the reaction order.