<p>If 0.22 g of a substance when vaporized displaced 45&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>c</mi><msup><mi>m</mi><mn>3</mn></msup></math>&nbsp;of air measured over water at 293 K and 755 mm pressure and if vapour pressure of&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mn>2</mn></msub><mi>O</mi><mo>&#160;</mo><mo>=</mo><mo>&#160;</mo><mn>17</mn><mo>.</mo><mn>4</mn></math>&nbsp;mm then the molar mass of the substance will be:</p>