Dear Preshanthan,

you should measure the effective reaction rate reff as a function of the partial pressure of the reactants. For first order kinetics (fast reactions) you can calculate henry's constant H according to:

reff=(a×p)/((RT/ka, g)+(H/ka, l Ha))

where a is the specific surface per volume, p is the partial pressure, ka, g is the mass transfer coefficient in the gas phase, ka, l is the mass transfer coefficient in the liquid phase and Ha is the Hatta-number

Best,

Sascha

Nehr's answer appears adequate. I recommend