In: Chemistry
A certain reaction has an activation energy of 39.79 kJ/mol. At what Kelvin temperature will the reaction proceed 6.50 times faster than it did at 339 K?
According to Arrhenius, we can relate the rate constants as following:
K = A*exp(-Ea/(RT))
Where:
K = rate constant at Temperature “T”
A = Frequency Factor
E = Activation Energy in J/mol
R = ideal gas constant, 8.314 J/mol-K
T = absolute temperature
Ahrrenius Equation 2 Points
From Ahrrenius equation;
K1 = A*exp(-Ea/(RT1))
K2 = A*exp(-Ea/(RT2))
Note that A and Ea are the same, they do not depend on Temperature ( in the range fo temperature given)
Then
Divide 2 and 1
K2/K1 = A/A*exp(-Ea/(RT2)) / exp(-Ea/(RT1))
Linearize:
ln(K2/K1) = -Ea/R*(1/T2-1/T1)
get rid of negative sign
ln(K2/K1) = Ea/R*(1/T1-1/T2)
substitute values and solve
K2 = 6.5*K1
K1 = K1
R = 8.314 J/molK
Ea = 39.79 kJ/mol = 39790 J/mol
T1 = 339 K, T2 = ?
substitute
ln(K2/K1) = Ea/R*(1/T1-1/T2)
ln(6.5*K1/K1) = 39790/8.314*(1/339-1/T2)
ln(6.5) = 39790/8.314*(1/339-1/T2)
ln(6.5)/39790 * 8.314 - 1/339 = -1/T2
T2 = -(-0.002558^-1) = 390.34 K
T2 = 390.34 K