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A gas filled in a bulb of capacity 25.1 mL at 27°C and 750 mm pressure weighs 0.072 g. If 1 litre of hydrogen at S.T.R weighs 0.09 g, calculate the molecular mass of the gas.

Answer» <html><body><p></p>Solution :Let the volume of the gas at STP be `V_(2)` mL <br/> `P_(1) = 750 <a href="https://interviewquestions.tuteehub.com/tag/mm-1098795" style="font-weight:bold;" target="_blank" title="Click to know more about MM">MM</a>, V_(1) = 25.1 mL, T_(1) = <a href="https://interviewquestions.tuteehub.com/tag/27-298706" style="font-weight:bold;" target="_blank" title="Click to know more about 27">27</a>^(@) <a href="https://interviewquestions.tuteehub.com/tag/c-7168" style="font-weight:bold;" target="_blank" title="Click to know more about C">C</a> = 300 K`<br/> `P_(2) = 760 mm, V_(2) = ?, T_(2) = 273 K` <br/> According to the gas equation: <br/> `(P_(1)V_(1))/T_(1) = (P_(2)V_(2))/T_(2)` or `V_(2) = (P_(1)V_(1)T_(2))/(T_(1)P_(2))` <br/> Substituting the values, we get <br/> `V_(2) = (750 xx 25.1 xx 273)/(300 xx 760)` <br/> = 22.5 mL <br/> Mass of 22.5 mL of `H_(2)` at S.T.P. <br/> `=0.09/1000 xx 22.5 = 2.025 xx 10^(-3) <a href="https://interviewquestions.tuteehub.com/tag/g-1003017" style="font-weight:bold;" target="_blank" title="Click to know more about G">G</a>` <br/> V.D. = `("Mass of 22.5 mL of gas at S.T.P")/("Mass of 22.5 mL of H_(2) at S.T.P")` <br/> `=0.072/(2.025 xx 10^(-3))` <br/> = 35.55 <br/> Hence, <a href="https://interviewquestions.tuteehub.com/tag/molecular-562994" style="font-weight:bold;" target="_blank" title="Click to know more about MOLECULAR">MOLECULAR</a> mass `=2 xx V.D. = 2 xx 35.55 = 71.1`</body></html>


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