Q116 / 200 · NEET 2022 (Phase 2) · Physics

Three vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains helium (monoatomic), the second contains fluorine (diatomic) and the third contains sulfur hexafluoride (polyatomic). The correct statement, among the following is:

  • A
    All vessels contain unequal number of respective molecules
  • B
    The root mean square speed of molecules is same in all three cases
  • Correct answer
    C
    The root mean square speed of helium is the largest
  • D
    The root mean square speed of sulfur hexafluoride is the largest

Solution

As, $\mathrm{V}_{\mathrm{rms}}=\sqrt{\frac{3 \mathrm{KT}}{\mathrm{m}}}$ Hence, $\quad v_{\mathrm{rms}} \propto \frac{1}{\mathrm{~m}}$ So, lower the mass, higher/greater the velocity. (where, the symbols have their usual meanings)

Hence, the correct answer is option: 'C'.

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