Element Symbol Atomic Mass
Barium Ba 137.327
Hydrogen H 1.00794
Oxygen O 15.9994
Hope this helps, good luck
Lower temperature
Let's verify
- Pressure=P
- volume=V
- Temperature=T
As per Boyles law

As per Charles law


So
At higher altitudes lower the pressure so lower the temperature
Number of mole : mass/ molar mass
87g/ (2 x 16) = 2.719 mol
volume = number of mole x molar volume
volume = 2.719 x 22.4
volume = 60.906 L