Given
Number of moles, n=4 mol
The temperature is T=290K
Mass of the gas, m=0.064 kg
Universal gas constant, R=8.31 J/mol.K
To find
The average speed of the molecule
Step-by-step explanation
The average speed is given by
![\begin{gathered} v=\sqrt{(3nRT)/(m)} \\ \Rightarrow v=\sqrt{(3*4*8.31*290)/(0.064)} \\ \Rightarrow v=672.19\text{ m/s} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/8q2ctyq4mp9xa0rm2e4ol6hijvbichevzw.png)
Conclusion
The average speed is B. 672 m/s