A reaction has a rate constant k=0.125 M^-1s^-1 at 298K and a rate constant k=0.210 M^-1s-1 at 350K. Estimate the rate constant for the reaction at -25 °C
T1 = 298.0 K
T2 = 350.0 K
K1 = 0.125 M-1s-1
K2 = 0.21 M-1s-1
use:
ln(K2/K1) = (Ea/R)*(1/T1 - 1/T2)
ln(0.21/0.125) = ( Ea/8.314)*(1/298.0 - 1/350.0)
0.52 = (Ea/8.314)*(4.99E-4)
Ea = 8651 J = 8.651 KJ
Now do the following.
T1 = 298.0 K
T2 = -25 oC = (-25 +273) K = 248.0 K
K1 = 0.125 M-1s-1
Ea = 8.651 KJ/mol = 8651.0 J/mol
use:
ln(K2/K1) = (Ea/R)*(1/T1 - 1/T2)
ln(K2/0.125) = (8651.0/8.314)*(1/298.0 - 1/248)
ln(K2/0.125) = -0.704
K2 = 0.0618 M-1S-1
Answer: 0.0618 M-1S-1
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