Where, R = the rate of the reaction (mol L⁻¹ s⁻¹) k = rate constant [X] and [Y] = concentrations of the reactants (mol L⁻¹) a = order of the reaction with respect to X b = order of the reaction with respect to Y overall reaction order, n = a + b
according to the given rate expression, rate = [a][b]³
order of the reaction with respect to 'a' is 1 order of the reaction with respect to 'b' is 3