Calculate the frequency of molecular collisions per square centimetre of surface in a vessel containing (a) hydrogen, (b) propane at 25°C when the pressure is (i) 100 Pa, (ii) 0.10 mTorr. What...

Calculate the frequency of molecular collisions per square centimetre of surface in a vessel containing (a) hydrogen, (b) propane at 25°C when the pressure is (i) 100 Pa, (ii) 0.10 mTorr. What pressure of argon gas is required to produce a collision rate of 8.5 × 10 20 s -1 at 450 K on a circular surface of diameter 2.5 mm?