89.5 Temperature-dependence of reaction rate Arrhenius equation Extensive reading: Levine, pp. 554-559 Section 17.8 oals 1. Describe the effect of temperature on reaction rate 2. Activation energy: definition, measurement, estimation 3. Fundamentals for higher level scientific researches
§9.5 Temperature-dependence of reaction rate -- Arrhenius equation Extensive reading: Levine, pp. 554-559 Section 17.8 Goals: 1. Describe the effect of temperature on reaction rate; 2. Activation energy: definition, measurement, estimation; 3. Fundamentals for higher level scientific researches
89.5 Arrhenius equation 9.5.1 Types of rate-temperature curves From the middle 19 century, people began to study the effect of temperature on the reaction rate ype Type ll Ty e l k qualitative Type I\ T pe
9.5.1 Types of rate-temperature curves From the middle 19 century, people began to study the effect of temperature on the reaction rate. qualitative T k T k T k T k T k Type I Type II Type III Type IV: Type V §9.5 Arrhenius equation
89.5 Arrhenius equation 9.5.2 The first quantitative study Ludwig Ferdinand wilhelmy V. Ueber das Gesete, nach welchen die Einwir tren auf den Rohrzucker stattfindet (Dec.25,1812,-Feb.18,1864) on Ludwig ilhelmy in Heid- a german scientist who is usually er die polarisationgebene des durch seine den Lichts nach rechtsdrehende Rohrzuel Ludwig Wilhelmy, Jacobus H. van't Hoff credited with publishing the first kanntlich durch Einwirknng von Siuren in li Svante Arrhenius und die Geschichte quantitative study in chemical kinetics heit der ablppelplatte nit grouser VEpor A Raison mir hierdurch die Moglichkeit gegeben, die G 1850, Wilhelmy studied the acid Rede stehenden Vorgangs zt catalyzed conversion of a sucrose m能装 solution into a 1:1 mixture of fructose aM. and glucose with a polarimeter. He wrote a differential equation to describe the od die ausdebnung der Ko der elektrischen und magnetischen Anziehung reaction. integrated it. and used it to sung- ihrem Werth nach abhangig sey v interpret his experimental results ae Wilhelmy found that the reactions rate was proportional to the concentrations of sucrose and of acid present
Ludwig Ferdinand Wilhelmy (Dec. 25, 1812, – Feb. 18, 1864) a German scientist who is usually credited with publishing the first quantitative study in chemical kinetics 1850, Wilhelmy studied the acidcatalyzed conversion of a sucrose solution into a 1:1 mixture of fructose and glucose with a polarimeter. He wrote a differential equation to describe the reaction, integrated it, and used it to interpret his experimental results. Wilhelmy found that the reaction's rate was proportional to the concentrations of sucrose and of acid present. 9.5.2 The first quantitative study §9.5 Arrhenius equation
89.5 Arrhenius equation 9.5.2 The first quantitative study ChOU+h,o C6H12o6+ Chloe sucrose glucose fructose In 1850, Wilhelmy determined the residual concentration of sucrose by measuring the r=k[ClH22Oul change of the rotation angle of a beam of plane-polarized light passing through the k=0.0043s hydrolysis solution with optical activity Substance sucrose glucosefructose k is quite low 25 +66.50+520 920 Does k' change with acid concentration?
C12H22O11 + H2O ⎯→ C6H12O6 + C6H12O6 sucrose glucose fructose Substance sucrose glucose fructose []D 25 +66.5 o +52 o - 92 o 12 22 11 r k = '[C H O ] k’ is quite low. In 1850, Wilhelmy determined the residual concentration of sucrose by measuring the change of the rotation angle of a beam of plane-polarized light passing through the hydrolysis solution with optical activity. 9.5.2 The first quantitative study §9.5 Arrhenius equation k = 0.0043 s-1 Does k’ change with acid concentration?
89.5 Arrhenius equation 9.5.3 Empirical rules inearization (1)vant'Hoff's Law dInk A It was found that for homogeneous reaction, an important generalization 入+ b quantitative is that reaction rate doubles or triples for every 10 degree increase in in which A and b are experimental empirical constants with their physical meaning unclear temperature T+10=2-3Semi-quantitative k 1884, vant'Hoff's equation: aIn K Difference between Experimental aT RT reports and Research paper
It was found that for homogeneous reaction, an important generalization is that reaction rate doubles or triples for every 10 degree increase in temperature. 10 2 ~ 3 T T k k + = 2 ln A B d k dT T = + in which A and B are experimental / empirical constants with their physical meaning unclear. 9.5.3 Empirical rules (1) vant’ Hoff’s Law Difference between Experimental reports and Research paper Semi-quantitative quantitative linearization 1884, vant’ Hoff’s equation: 2 ln r m p K H T RT = §9.5 Arrhenius equation