Zero Order of Reaction: Experiment 8 Chemical Kinetics: Zero Order of Reaction: Iodination of Acetone

Theory: A reaction is said to be of zero order if its rate is entirely independent of the concentration of the reactants

If the rate is independent of [A]  -dC/dt = k Theory: If the rate is independent of [A]  -dC/dt = k k= 𝐶ₒ −𝐶 𝑡  t = 𝐶ₒ −𝐶 𝑘 When t = 𝑡 1 2  C = Cₒ 2 𝑡 1 2 = Cₒ − − Cₒ 2 k = 2Cₒ −Cₒ 2 k 𝑡 1 2 = Cₒ 2k Where : Cₒ: Initial Concentration K: Rate Constant of Zero Order (Unit: 𝑴 𝑺 −𝟏 ) 𝒕 𝟏 𝟐 : Half life time

Theory: C O CH3 H3C acetone CH2I + I2 + HI + H+ H+ Step (1)  (CH3)2C=O + H+   (CH3)2C=O+H Slow SLOW protonation of the aceton is the rate determining step. Step (2)  (CH3)2C=O+H    CH3C(OH)=CH2 + H+ Fast Step (3)  CH3C(OH)=CH2 + I2   CH3COCH2I + HI Fast If aceton is taken in large excess, its concentration may be taken to be constant -d[I₂]/dt = k  -d[I₂]= k dt  [I₂]= - k t + [I₂]ₒ Where [I₂]ₒ : Initial concentration of I₂

10 mL I2 (0.1N) 10 mL acetone 10 mL H2SO4(0.1N) 70 mL H2O

Na2S2O3 (0.004 N) Starch indicator Mixture of acetone, H2SO4, H2O and I2 10 mL of Mix. 5 mL NaHCO3

decrease Results: t, min. Vt ml of Na₂S₂O₃ [I2], N 3 6 9 12 15 18 21 24 27 30 N X V (NaS₂O₃)= Nʹ x Vʹ(I₂) [I₂] = Nʹ= N X V (NaS₂O₃) Vʹ [I₂]=Nʹ= 0.004 X Vt (Burtte) 𝟏𝟎 decrease

[I₂] = - k t + [I₂]ₒ y Slope X Intersept [I₂]ₒ [I₂], N 𝒕, 𝐦𝐢𝐧. Graph: Law of Zero Order of Reaction [I₂] = - k t + [I₂]ₒ y Slope X Intersept [I₂]ₒ Intersept Slope = - k k= - 𝒔𝒍𝒐𝒑𝒆 = ? Unit of k: 𝑵 𝒎𝒊𝒏. −𝟏 Intercept= [I₂]ₒ= ?, N 𝒕 𝟏 𝟐 = [I₂]ₒ 2k = ? 𝒎𝒊𝒏. [I₂], N Slope 𝒕, 𝐦𝐢𝐧.