20 Ammonia reacts with oxygen in the presence of a copper ca

20. Ammonia reacts with oxygen in the presence of a copper catalyst to form nitrogen and water. When the

temperature is increased from 164.5

Solution

Use the Arrhenius equation to solve this. It relates rates of reactions at two different temperatures if you know the activation energy (Ea).

ln(k2/k1) = (Ea/R) * ((T2-T1)/(T1*T2)) where k1 and k2 are the rate constants at temperatures T1 and T2. R is a constant = 8.314 J/mol K. The ratio of k2/k1 = 4.27 in this question. The units of temperature must be Kelvin and Ea is in J/mol (not kJ). Solving for Ea the equation looks like:

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

Ea = ((437.6 * 452.1)/(452.1-437.6))*8.314*ln(4.27)

Ea = 164666 J/mol = 165 kJ/mol