Question

The isomerization of methyl isocyanide, CH₃NC - CH₃CN, follows first-order kinetics. The half-lives were found to be 161 min at 199°C and 12.5 min at 230°C. Calculate the activation energy for this reaction. (R-8.314 J/mol K) 

• 124 kJ/mol 

• 6.17 x 10-3kJ/mol 

• 78.2 kJ/mol 

• 163 kJ/mol 

• 31.4 kJ/mo

Answer 1

* using Arrhenius Equation in e in) = -fan het Taz 199+ 273 = 472 K T2 = = 230 +273 = 503K - Ea in 1925) 14 442) I 472 8.314 503 2.556 -fa - 472 - 503 8.314 sos mome) 503X472 21.24784503X472 Ea 31 Ea a 162727 g/mol Ecua 163 kJ/mol Actiration energy of the reaction Ea= 16 kylmol

ki is rate constant K₂ is rate constant at temperature to at temperature T2 Ea is activation energy A is frequency factor ki = A FAIRT, K2 = A Ea/RT2 -Ea/RT Ke EatRly 2-4) ki - е the Eartz

KL= 0.693 0-693 161 min 0.004304 min fya K2 = 0.693 0-693 12.5 min O. 05544 min 0.004302 gmin' 0.05544 min 412.15 Fairt-0.000130495% 0.077633 = e Take In on both sides - Ea X0.000 13049 fonco. 077633) = Ine RK +2.55596 = /Fax.:.00013044 8.314 5 betmoils EQ = 2-5557668-314 Jmoil 0.00013049 = 162.8369 kJ/mol 163 KTimel omhan is the answey. The name given to slowext step in the mechanium is "Rate determining step". 50

Answer 2

* using Arrhenius Equation in e in) = -fan het Taz 199+ 273 = 472 K T2 = = 230 +273 = 503K - Ea in 1925) 14 442) I 472 8.314 503 2.556 -fa - 472 - 503 8.314 sos mome) 503X472 21.24784503X472 Ea 31 Ea a 162727 g/mol Ecua 163 kJ/mol Actiration energy of the reaction Ea= 16 kylmol