Modern vacuum pumps can evacuate a vessel down to a pressure of \[4.0\times {{10}^{-15}}\text{ }atm.\]at room temperature (300 K). Taking , \[1\text{ }atm=105\text{ }Pa\]and \[{{N}_{avogadro}}=6\times {{10}^{23}}mol{{e}^{-1}},\] the mean distance between molecules of gas in an evacuated vessel will be of the order of:

• A. 0.2 urn
• B. 0.2 mm
• C. 0.2 cm
• D. 0.2 nm