According to kinetic- molecular theory, in which of the following gases will the root- mean- square speed of the molecules be the highest at 200 °C? A) HCl B) Cl₂ C) SF₆ D) H₂O E) None. The molecules of all gases have the same root- mean- square speed at any given temperature.

Question

Quizplus · Accepted Answer

According to kinetic-molecular theory, the root-mean-square speed of gas molecules is directly proportional to the square root of the temperature and inversely proportional to the square root of its molar mass. Among the given options, HCl, Cl2, SF6 have higher molar masses than H2O, which is the molar mass of H2 at about 200°C. Therefore, H2O gas will have the highest root-mean-square speed of molecules. Among the given options, only HS and HCl have H atoms. As sulfur is heavier than chlorine, HS has a higher molar mass than that of HCl. Therefore, HS gas will have a lower root-mean-square speed of molecules than HCl. So, the only option left is D, i.e., H2O.

According to Kinetic- Molecular Theory, in Which of the Following