The atomic mass is the average mass of all the isotopes. The atomic number is the number of protons in the nucleus of an atom. In an uncharged atom the atomic number is also equal to the number of electrons.
Hope this helps!
1.7960L
Explanation:
the mass of the gas is constant in both instances
pv/T=constant(according to pv=nRT)
745mmHg*2L/298K=760mmHg*v/273K
v=1.7960L