I believe you just look at your periodic table for this value. I don't think there is any math involved.
Therefore one mole of Mg = 24.305g.
This change in pressure is caused by changes in air density, and air density is related to temperature.
I always thought it was a mixture but can also be a compound
ACID: A substance that accepts a lone pair of electrons
BASE: A substance that donates a lone pair of electrons
:D