The atomic mass of an element is a. the sum of the protons and neutrons in one atom of the element. b. twice the number of protons in one atom of the element. c. a ratio based on the mass of a carbon-12 atom. d. a weighted average of the masses of an element’s isotopes.

The atomic mass of an element is D. a weighted average of the masses of an element’s isotopes.

The sum of the protons and neutrons in one atom of the element is the mass number.

A ratio based on the mass of a carbon-12 atom gives the atomic mass in unified atomic mass units (u),

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.