Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...
Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ... Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...
2.3 Kinetics of reversible first-order reactions (relaxation processes) 23 I Relaxation processes: • The transition from a deviation from equilibrium into the equilibrium is called relaxation. • ( 1 + −1 ) −1 has the dimension of time and is called the relaxation time, =( 1 + −1 ) −1 (2.78) • The temporal evolution of relaxation processes from a nonequilibrium to the equilibtium state is determined by the sum of the respective forward and reverse rate constants!
2.4 Kinetics of second-order reactions 24 2.4 Kinetics of second-order reactions 2.4.1 A + A → products A+A→ P (2.79) I Solution of the rate equation: Integration: y Initial value condition at =0: − 1 [A] = [A] 2 (2.80) 2 [A] 2 = −2 (2.81) [A] − 1 = −2 + (2.82) [A] [A ( =0)]=[A] 0 (2.83) y Solution for [A ()] (Fig. 2.15): = − 1 [A] 0 (2.84) 1 [A] = 1 +2 (2.85) [A] 0 I Experimental determination of k: (1) Graphical method: 1 [A] = 1 [A] 0 +2 (2.86) ⇒ Plot of [A] −1 vs. gives a straight line with slope =2 (Fig. 2.9). ⇒ We do need to know the absolute concentration of [A]! (2) We can again use a nonlinear least squares fitting method (Appendix B).
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2.3 <strong>Kinetics</strong> of reversible first-order reactions (relaxation processes) 23<br />
I<br />
Relaxation processes:<br />
• The transition from a deviation from equilibrium into the equilibrium is called<br />
relaxation.<br />
• ( 1 + −1 ) −1 has the dimension of time and is called the relaxation time,<br />
=( 1 + −1 ) −1 (2.78)<br />
• The temporal evolution of relaxation processes from a nonequilibrium to the equilibtium<br />
state is determined by the sum of the respective forward and reverse rate<br />
constants!
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