5.5. Pressure of l g of an ideal gas A at 27°C is found to be 2 bar. When 2 g of another ideal gas B is introduced in the same flask at same temperature, the pressure becomes 3 bar. Find the relationship between their molecular masses.

<p><strong>5.5.&nbsp;</strong>Suppose molecular masses of A and B are M_A&nbsp;and M_B&nbsp;respectively. Then their number of moles will be</p><p>n_A= 1/M_A &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; n_B = 2/M_B</p><p>Given: P_A = 2 bar&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; and P_A + P_B = 3 bar</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =&gt; P_B = 1bar</p><p>Since, PV = nRT</p><p>P_A= n_ART and P_BV= n_BRT</p><p>Therefore, (P_A / P_B) = (n_A / n_B)= (M_B / 2M_A)</p><p>=&gt; M_B / M_A= 2 x P_A / P_B= 2 x 2 /1 = 4</p><p>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; =&gt; M_B = 4 M_A</p>

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