Arrhenius Equation Problems.... 1. The diagram below shows Arrhenius plots for t

Question

Arrhenius Equation Problems....

1. The diagram below shows Arrhenius plots for two chemical reactions (labeled A and B). Which reaction has the larger activation energy? Briefly explain 2. The slope of the Arrhenius plot for a reaction is-2.5x 10 K. What is E, for the reaction in k/mol? IR 8.3145 J/mol K). 3. The activation energy for a reaction between CO and NO2 is determined to be 134 k. a) By what factor does the rate constant change for a 10° change in temperature (e.g. 700 to 710 b) Does the rate constant increase or decrease with increasing temperature? Briefly explain. 4. Indicate the effect a change in the following reaction conditions has an the reaction rate and the rate constant (assume a first order or higher rate law). Possible answers are: increase, decrease, nane. Variable Increased temperature Decreased reactant concentration Addition of a catalyst Increased solution ionic strength/polarity (for a reaction between two anions, as in lab Effect on reaction Rate Effect on rate constant

Explanation / Answer

1) in Arrhenius plot, ln K = (-Ea/R)(1/T) + ln A is a straight line where -Ea/R corresponds to the slope of the line.

   slope of the line = -Ea/R

since R is a constant for both Arrhenius plots A and B, we can compare the slope based on -Ea. The higher the slope, the higher the value of Ea. Based on the graph, B has a higher slope compared to A, thus B has higher Ea.

2. slope = -Ea/R, Ea = slope*R = -2.5E4*-8.314 J = 207.85 kJ/mol

3. to determine the effect temperature, we need to get the value of e-Ea/RT for both temperatures.

   at 700K: e-Ea/RT = e-134kJ/(8.314J/mol-K)(700K) = 1.00E-10

at 710K : e-Ea/RT = e-134kJ/(8.314J/mol-K)(710K) = 1.38E-10

so in the rate constant change by a factor of 1.38

b. Yes! because increasing the temperature increases the reaction rate. As the temperature increases, energy is provided for the reaction to proceed.

4. a. increase, increase

b. decrease, none

c. increase, none

d. increase, none

  

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