Question

Calculate the activation energy for the reaction between hydrogen gas and iodine gas to form hydrogen iodide, given that the rate constant at 25°C is 4.2 × 10^-4 L/mol.s and the frequency factor is 1.5 × 10^12 s^-1.

Answer 1

To calculate the activation energy, we can use the Arrhenius equation:k = Ae^-Ea / RT Where:k = rate constant  4.2  10^-4 L/mol.s A = frequency factor  1.5  10^12 s^-1 Ea = activation energy  which we want to find R = gas constant  8.314 J/mol.K T = temperature in Kelvin  25C = 298K First, we need to isolate Ea in the equation:k / A = e^-Ea / RT Now, take the natural logarithm of both sides:ln k / A  = -Ea / RTNext, multiply both sides by -RT:Ea = -RT * ln k / A Now, plug in the values:Ea = -  8.314 J/mol.K  *  298 K  * ln  4.2  10^-4 L/mol.s  /  1.5  10^12 s^-1  Ea  -  8.314 J/mol.K  *  298 K  * ln 2.8  10^-16 Ea  173,000 J/molThe activation energy for the reaction between hydrogen gas and iodine gas to form hydrogen iodide is approximately 173 kJ/mol.