Question

give reason volume of different gases are converted to STP before comparing their densities

Answer 1

Since volumes of gases change with temperature and pressure, a standard value of temperature and pressuure is chosen to which gas volumes are referred. Hence volumes of gases are converted into S.T.P. conditions

Answer 2

Since volumes of gases change with temperature and pressure, a standard value of temperature and pressuure is chosen to which gas volumes are referred. Hence volumes of gases are converted into S.T.P. conditions and then compared easily.
~Regards,Renuka.
19th ICSE student.