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A reaction has a rate constant of(0.000122)/(s)at27\\\\deg Cand(0.228)/(s)at77\\\\deg C.\\na) Determine the activation barrier (activation energy) for the reaction.\\nb) What is the value of the rate constant at9\\\\deg C?

Question

A reaction has a rate constant of(0.000122)/(s)at27\\deg Cand(0.228)/(s)at77\\deg C.\na) Determine the activation barrier (activation energy) for the reaction.\nb) What is the value of the rate constant at9\\deg C?

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Solution

a) To determine the activation energy (Ea) of the reaction, we can use the Arrhenius equation in the form of:

k = A * e^(-Ea/RT)

where: k is the rate constant, A is the pre-exponential factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.

However, since we have two sets of k and T, we can form two equations and divide one by the other to eliminate A. This gives us:

k1/k2 = e^((Ea/R)*(1/T2 - 1/T1))

We can rearrange this to solve for Ea:

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

Substituting the given values (R = 8.314 J/(mol*K), k1 = 0.000122 s^-1, T1 = 27°C = 300.15 K, k2 = 0.228 s^-1, T2 = 77°C = 350.15 K), we get:

Ea = 8.314 * ln(0.000122/0.228) / (1/350.15 - 1/300.15)

Calculating this gives us the activation energy in J/mol.

b) To find the rate constant at 9°C, we can use the Arrhenius equation again, but this time solve for k:

k = A * e^(-Ea/RT)

We don't know A, but we can express it in terms of k1, Ea, and T1:

A = k1 / e^(-Ea/RT1)

Substituting this into the equation for k gives us:

k = k1 * e^(-Ea/R * (1/T - 1/T1))

Substituting the given values (k1 = 0.000122 s^-1, Ea from part a, R = 8.314 J/(mol*K), T = 9°C = 282.15 K, T1 = 300.15 K) gives us the rate constant at 9°C.

This problem has been solved

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