Styles 13. The rate constant for the decomposition of a certain substance is 1.7
ID: 703770 • Letter: S
Question
Styles 13. The rate constant for the decomposition of a certain substance is 1.70x102Lmol s1 at24°C and 2.01x102L mol's t at 37°C. Determine the Ahenius parameters A and Ea 14. Consider the following overall reaction for the conversion ofNO to N20: 2NO (g) + H 2(g)--> N20(g) + H2O(g) After years of study, and the identification of a likely intermediate, the following multistep mechanism was proposed Assuming that a steady state population ofthe intemmediate is quickly fomed, detemine the overall rate law for the consumption ofhydrogen.Explanation / Answer
Ans 13
Rate constant k1 = 1.70*10^-2 L/mol-s
Temperature T1 = 24 + 273.15 = 297.15 K
Rate constant k2 = 2.01*10^-2 L/mol-s
Temperature T2 = 37 + 273.15 = 310.15 K
From Arrhenius equation
k1 = A x exp (-Ea/RT1)
k2 = A x exp (-Ea/RT2)
Divide above equation and take natural logarithm in both sides
ln (k2/k1) = (Ea/R) (1/T1 - 1/T2)
ln (2.01*10^-2 / 1.70*10^-2) = (Ea/8.314) (1/297.15 - 1/310.15)
0.16751 = Ea x 0.000016966 x 10^-5
Ea = 9873.13 J/mol
Ea = 9.873 kJ/mol
k2 = A x exp (-Ea/RT2)
A = k2 / exp (-Ea/RT2)
= (2.01*10^-2) / (exp(-9873.13/8.314*310.15)
= (2.01*10^-2) / (0.02173568)
= 0.9247 L/mol-s