The lowest pressure attainable using the best available vacuum techniques is about 10^−12 n/m^2.

at such a pressure, how many molecules are there per cm^3 at 19 °c?

247 molecules

Explanation:

This problem can be solved by using the ideal gas equation:

where in this case we have

is the lowest pressure attainable

is the volume we are considering

n is the number of moles

R is the gas constant

is the absolute temperature

Solving the equation for n, we find

And since the number of molecules in 1 mole of gas is

(avogadro number)

The number of molecules present here is

so, there are approximately 247 molecules.

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