For the discovery of the elements polonium and radium. Prohibited from higher education in her native Poland (then controlled by Russia), she moved to Paris in 1891 and studied at the Sorbonne.
I THINK this is the answer: 4809.35999999786. (found it on a website)
Sorry I’m only answering so I could upload
Using ideal gas equation,

Here,
P denotes pressure
V denotes volume
n denotes number of moles of gas
R denotes gas constant
T denotes temperature
The values at STP will be:
P=1 atm
T=25 C+273 K =298.15K
V=663 ml=0.663L
R=0.0821 atm L mol ⁻¹
Mass of gas given=1.25 g g
Molar mass of gas given=?


Putting all the values in the above equation,

Molar mass of the gas=46.15