To determine the temperature at which 25% of the molecules have energy greater than or equal to Ea, we need to assume a certain energy distribution function. In this case, we can assume a Maxwell-Boltzmann energy distribution function.
The Maxwell-Boltzmann distribution describes the distribution of speeds (energies) of particles in a system at a given temperature. According to this distribution, the fraction of molecules with energy greater than or equal to a certain energy Ea is given by:
f(E) = exp(-Ea / kT)
Where f(E) is the fraction of molecules with energy greater than or equal to Ea, k is Boltzmann's constant (1.38 × 10^-23 J/K), and T is the temperature in Kelvin.