The average kinetic energy of an ideal gas is calculated as
KE_avg = 3/2 kT
where T is the temperature in Kelvin and k=R/N_A; R is the universal gas constant and N_A is the number of moles.
Thus, upon substitution we get
KE_avg = 3/2(8.314/1)(100+273)
KE_avg = 3/2(8.314)(373)
KE_avg = 4651.683
The average kinetic energy of 1 mole of a gas at 100 degree Celsius is 4651.683 J.