中山大学及北京师范大学编写的《无机化学实验》中,有过二硫酸铵与碘化钾反应速度的测定实验.在水溶液中,该反应的离子反应式为: S_2O_8~2+3I~-=2SO_4~(2-)+I_3~-(1)+I_3~(1)反应速度方程可表示为: v=k[S_2O_3~(2-)]~m[I~-]~n(2)式中V是反应的瞬时速度,若[S_2O_8~(2-)]、[I~-]是起始浓度,则V表示起始速度.但实验测定的是在时间Δt内反应的平均速度V,在此时间内S_2O_8~(2-)浓度的改变量为Δ[S_2O_8~(2-)],故有V=-Δ[S_2O_8~(2-))]/(Δt))(3)显然,只在Δt很小时,才能平均速度代替起始 Sun Yat-sen University and Beijing Normal University, “inorganic chemistry experiment”, there is a determination of the reaction rate of ammonium sulfate and potassium iodide in aqueous solution, the reaction of the ionic reaction formula: S_2O_8 ~ 2 + 3I ~ - = 2SO_4 ~ (2 -) + I_3 ~ - (1) + I_3 ~ (1) The reaction rate equation can be expressed as: v = k [S_2O_3 ~ (2 -)] ~ m [ Is the instantaneous velocity of the reaction, and [S_2O_8 ~ (2 -)], [I ~ -] is the initial concentration, then V is the initial velocity, but the experimentally determined is the average velocity V of the reaction in time Δt, (2)] / (Δt)) (3) Obviously, the change of concentration of S_2O_8 ~ (2-) is Δ [S_2O_8 ~ (2-) When Δt is small, the average speed can be substituted for the start