1. The rate constants for the reaction 2 N2O5(g) 4 NO2(g) + O2(g) is measured at
ID: 887616 • Letter: 1
Question
1. The rate constants for the reaction 2 N2O5(g) 4 NO2(g) + O2(g) is measured at two temperatures: Show your calculations and show the units
a) What is the activation energy (in kJ / mol) for the reaction?
b) Given the rate constant at 330 oC and the value of Ea obtained in part a), what is the rate constant at 340 oC?
2. You are asked to determine the amount of salicylic acid expressed in molar concentration ([Sal]) in an unknown sample of aspirin. You decide to use an UV-Vis spectrometer absorption method and run the following standards of Sal to construct a calibration curve.
Calculate: a. Use the excel program and prepare the plot Absorbance vs. [Sal].
b. Determine the equation for the best least squares fit (calibration equation).
c. Determine the concentration of salicylic acid in mol/L in your unknown sample of aspirin.
t(oC) k ( L/mol min) 330 0.77 378 4.1Explanation / Answer
Answer: From: logK = logA-[Ea/(2.303RT)]
Ea = (RT1T2)*2.303/(T1-T2)][logK1/K2)
=(8.314*603*651)*(2.303)/(603-651) log (0.77/4.1)
=[156588.9]*log(0.188)
=116588 J
Rate constant at 330 0C =0.77
Ratw constant at 340 0C = X
logk1/k2 = T2/T1
log(0.77/x) = 613/603
(0.77/x)= Anti-log(1.02)
(0.77/x) = 10.5
x = 0.77/10.5
=0.07
Rate constant at 340 0C = 0.07
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