Question

An engineer is testing vacuum pumps. The pumps are connected to a vacuum chamber with a volume of 1.70 m3, allowed to run for a set period of time, and the temperature and pressured measured. For a particular pump, the final chamber temperature and pressure are respectively measured to be 295 K and 5.00 ✕ 10−10 Torr (where 1 Torr = 133 Pa). Determine the number of molecules in the chamber at the end of the pumping time. You may treat the contents of the vacuum chamber as an ideal gas.

Answer 1

using ideal gas equation

PV = n RT

where P is the pressure , V is the volume, n is the number of moles, R is the gas constant, T is the temperature.

substitute the given values

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