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Understanding the high-temperature behavior of nitrogen oxides is essential for

ID: 1002950 • Letter: U

Question

Understanding the high-temperature behavior of nitrogen oxides is essential for controlling pollution generated in automobile engines. The decomposition of nitric oxide (NO) to N2 and O2 is second order with a rate constant of 0.0796 M1s1 at 737C and 0.0815 M1s1 at 947C. You may want to reference ( pages 593 - 598) Section 14.5 while completing this problem.

Calculate the activation energy for the reaction. Express the activation energy in kilojoules per mole to three significant digits.

Ea = kJ/mol

Explanation / Answer

we know that

according to arhenius equation

ln (k2/k1) = (Ea/R) (1/T1 - 1/T2)

given

k2 = 0.0815

T2 = 947 + 273 = 1220

k1 = 0.0796

T1 = 737 + 273 = 1010

so

using those values

we get

ln ( 0.0815 / 0.0796) = (Ea / 8.314) ( 1/ 1010 - 1/1220)

Ea = 1150
  

Ea = 1.15 x 1000

so

the activation energy (Ea) is 1.15 kJ/mol