According to Avogadro's law, the volume of an ideal gas is directly proportional to the number of moles. We can calculate the final volume of the balloon using the following expression.
In organic chemistry the boiling point of 309 k is of fifth member of alkane series which Pentane whose molecular mass is 72 g/mol. Thus, we can say that the molecular formula of the compound which has boiling point 309 K is C5H12.
