Compare the mass number and atomic number for isotopes of an element

19. at high pressures, how does the volume of a real gas compare with the volume of an ideal gas under the same conditions, and why? eman- it is much less because real gas partides are not moving. there is no difference because the gas laws are always obeyed. it is much less because at high pressures the temperature drops. it is much greater because real gas partides take up space.

Given the following at 25c calculate delta hf for hcn (g) at 25c. 2nh3 (g) +3o2 (g) + 2ch4 (g) > 2hcn (g) + 6h2o (g) delta h rxn= -870.8 kj. delta hf=-80.3 kj/mol for nh3 (g), -74.6 kj/mol for ch4, and -241.8 kj/mol for h2o (g)

Iwould appreciate if someone could me.