CHEM 1332 1st Edition Lecture 8 Outline of Last Lecture - Rate Law- Order- Half-lifeOutline of Current Lecture - Arrhenias equation- Example of a problem- Submicroscopic scale Current Lecture- The rate of a reaction can be affected by the concentration- The reaction is also affected by temperature- As temperature increases rate law increases - Arrhenias equation is k =A e−Ea/ RT - A is the Arrhenias constant also known as the frequency constant and it depends on the reaction- Ea is the activation energy and it depends on the reaction- R is the gas constant and here it is 8.314 J/mol k- T is temperature in Kelvin- If we take ln the new equation is ln k =ln A−EaRT- The variables are k and temperature- k is proportional to f(T)-- If we were to do the reaction at two temperatures T1 would go to k1 and T2 would go tok2 These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-ln k 1=ln A−EaRT 1 and ln k 2=ln A−EaRT 2- If we were to subtract them both we would be left with k 1−ln k 2=¿−EaRT 1+EaRT 2ln ¿- Simplifying the equation we will have lnk 1k 2¿−EaR(1T 2−1T 1)- An example is a reaction at k=0.2 sec−1 at 25 degrees Celsius and k=0.4 sec−1 at 35 degrees Celsius find the activation energy in kJ- We plug it in and get ln0.40.2¿−Ea8.134(1308−1298)-ln 0.693 ¿−Ea8.134(0.000108951 )- Ea=52882 J- Ea=52.9 kJ- Submicroscopic scale if we take the reaction NO+CO2→ NO2+CO- The rate would be given and it is CO2rate =k[NO]¿]-- i) Breaking bonds is endothermic you need energy- ii) Making new bonds is exothermic - To start a reaction you need energy- The collision energy has to be greater than the activation energy for the reaction to occurKey TermsActivation energy- minimal energy needed for the reaction to take
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