Question

Suppose you are given two flasks at the same temperature, one of volume 2 L and the other of volume 3 L. The 2-L flask contains 4.8 g of gas, and the gas pressure is X atm. The 3-L flask contains 0.36 g of gas, and the gas pressure is 0.1X. Do the two gases have the same molar mass? If not, which contains the gas of higher molar mass?

Answer 1

Explanation:

The given data is as follows.

         $V_{1}$ = 2 L,     $V_{2}$ = 3 L,        

        $P_{1}$ = X,          $P_{2}$ = 0.1 X,

       $m_{1}$ = 4.8 g,       $m_{2}$ = 0.36 g,

      $M_{1}$ = ?,              $M_{2}$ = ?

According to the ideal gas equation,

     $\frac{P_{1}V_{1}M_{1}}{m_{1}} = \frac{P_{2}V_{2}M_{2}}{m_{2}}$

    $\frac{X \times 2 \times M_{1}}{4.8 g} = \frac{0.1X \times 3 \times M_{2}}{0.36 g}$  

           $\frac{M_{1}}{M_{2}} = \frac{4.8 \times 0.1 \times 3}{2 \times 0.36}$

                            = 2

or,              $M_{1} = 2 \times M_{2}$

Thus, we can conclude that two gases does not have the same molar mass and flask 1 contains a gas of higher molar mass.