The eight most common elements in earth's crust are: o, si, al, fe, ca, na, k, and mg. these elements account for 98% of the atoms in earth's crust. these eight elements combine chemically with one another to make six main minerals which account for 90% of the minerals in earth's crust. these minerals, the so-called the rock forming minerals, are: feldspar, pyroxene, amphibole, mica and the last, made up of the two most abundant elements, is

the ideal gas law equation is as follows

pv = nrt

where p - pressure

v - volume

n - number of moles

r - universal gas constant

t - temperature

so if the pressure, volume and temperature are already known

we are left with n and r

since r is the universal gas constant that has a known fixed value then r too is known

so we are left with 'n'

once we know temperature volume and pressure

we can find the number of moles of gas present using the ideal gas law equation

this is not my own answer, this is an answer for the same question by the user blahblahmali. i do not claim ownership of this account.