Using ideal gas equation,
[tex]P\times V=n\times R\times T[/tex]
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=?
[tex]Number of moles of gas, n= \frac{Given mass of the gas}{Molar mass of the gas}[/tex]
[tex]Number of moles of gas, n= \frac{1.25}{Molar mass of the gas}[/tex]
Putting all the values in the above equation,
[tex]1\times 0.663=\frac{1.25}{Molar mass of the gas}\times 0.0821\times 298.15[/tex]
Molar mass of the gas=46.15