[tex]T=0^oC=273,15 \ K \\ \vec{v}_T=493 \ m/s \\ R=8,31 \ J/(mol\cdot K) \\ \vec{v}_T=\sqrt{\frac{3RT}{M}} \Longleftrightarrow \frac{3RT}{M}=(\vec{v}_T)^2 \\ \Rightarrow M=\frac{3RT}{(\vec{v}_T)^2}=\frac{3 \cdot 8,31 \ J/(mol\cdot K) \cdot 273,15\ K}{(493 \ m/s)^2} \\ M=\frac{6\ 809,6295}{243\ 049} \\ \Rightarrow \boxed{M=0,028 \ g/mol}[/tex]
