a storage tank contains 21.6kg of nitrogen (N2) at an absolute pressure of 3.65 atm. What will the pressure be if nitrogen is replaced by an equal mass of CO2?
moles of N2 = 21600g / 28g/mol = 771 mol
CO2 has weight 12 + 2*16 = 44g/mol,
so moles of CO2 = 21600g / 44g/mol = 491 mol
For temperature constant, the new pressure is
p = 3.65atm * 491/771 = 2.32 atm