It was stated that at room temperature (25oC) the majority of molecules are in the ground vibrational energy level (v=0).
a) Use the Boltzmann equation to calculate the excited-state and ground-state population ratios for HCl: N(v=1)/N(v=0). The fundamental vibrational frequency of HCl occurs at 2885 cm-1.
b) Use the results of part a) to find N(v=2)/N(v=0)