Q32 / 160 · NTA Abhyas (JEE Main) 2020 · Physics · Thermodynamics

The root mean square rms speed of oxygen molecules (O2) at a certain temperature T (on kelvin scale) is V. If the temperature is doubled and oxygen gas dissociates into atomic oxygen, the rms speed becomes

  • Correct answer
    A
    two times
  • B
    three times
  • C
    four times
  • D
    unchanged

Solution

                     V rms = 3RT M

                     V rms ∝ T M                               ...(i)

When oxygen gas dissociates into atomic oxygen, its
atomic mass M will become half.
Temperature is doubled.
So, from Eq. (i) Vrms will become two times.

Vrms'Vrms=2TM2TM

= 4 =2

⇒Vrms'=2Vrms

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

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