Arun
Last Activity: 4 Years ago
The final pressure after evacuation is given in mm Hg and hence has to be converted to atm.
760 mm Hg = 1 atm
thus 0.001 mm Hg = 1. 31 x 10-6 atm.
As we know that at STP conditions 1 Mole of a substance occupies 22.4 L of volume and contains 6.022 x 1023 molecules
Here the volume occupied at STP = 1 Litre.
Thus no. of moles = 1/22.4 = 0.044 Moles of methanol and no. of molecules = 0.044 x (6.022 x 1023) = 2.68 x 1022
Hence, at 1.31 x 10-6 atm pressure, no. of molecules will be
= (2.68 x 1022 ) x (1.31 x 10-6)
Thus no. of molecules = 3.51 x 1016
