Q100 / 125 · BITSAT 2014 · Physics

Two balloons are filled one with pure he gas and other with air respectively. If the pressure and temperature of these balloons are same, then the number of molecules per unit volume is

  • A
    more in He gas filled balloon
  • Correct answer
    B
    same in both balloons
  • C
    more in air filled balloon
  • D
    in the ratio 1: 4

Solution

Assuming the balloons have the same volume, as $\mathrm{pV}=\mathrm{nRT}$. If $\mathrm{P}, \mathrm{V}$ and $\mathrm{T}$ are the same, $\mathrm{n}$ the number of moles present will be the same, whether it is He or air. Hence, number of molecules per unit volume will be same in both the balloons.

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

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