Consider the gas law:

$\overline{){\mathbf{P}}{\mathbf{V}}{\mathbf{=}}{\mathbf{n}}{\mathbf{R}}{\mathbf{T}}}$, where n is the number of moles and R is the gas constant given by, R = 8.314 J•K^{-1}

The number of molecules is given by:

$\overline{){\mathbf{N}}{\mathbf{u}}{\mathbf{m}}{\mathbf{b}}{\mathbf{e}}{\mathbf{r}}{\mathbf{}}{\mathbf{o}}{\mathbf{f}}{\mathbf{}}{\mathbf{m}}{\mathbf{o}}{\mathbf{l}}{\mathbf{e}}{\mathbf{c}}{\mathbf{u}}{\mathbf{l}}{\mathbf{e}}{\mathbf{s}}{\mathbf{=}}{\mathbf{n}}{{\mathbf{N}}}_{{\mathbf{A}}}}$, where N_{A} is Avogadro's number.

The lowest pressure attainable using the best available vacuum techniques is about 10^{-}^{12}N/m^{2}.

At such pressure, how many molecules are there per cm^{3} at 13 °C?

Express your answer using two significant figures.

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