question_answer

Modern vacuum pumps can evacuate a vessel down to a pressure of \[4.0\times {{10}^{-15}}\]atm. at room temperature (300 K). Taking \[\text{R=8}\text{.0J}{{\text{K}}^{\text{-1}}}\text{mol}{{\text{e}}^{\text{-1}}}\text{,1atm=1}{{\text{0}}^{\text{5}}}\text{Pa}\] and\[{{\text{N}}_{\text{Avogadro}}}=6\times {{10}^{23}}\text{mol}{{\text{e}}^{-1}},\]the mean distance between molecules of gas in an evacuated vessel will be of the order of:                                                   [JEE ONLINE 09-04-2014]

A)  0.2 mm           

B)       0.2 mm

C)  0.2 cm

D)       0.2 nm