Answer:
Step-by-step explanation:
Total moles = 300 + 500 = 800 moles
mole fraction of carbon dioxide = 300 / 800 = 3 / 8
water = 500 / 800 = 5 / 8
Total pressure = 21 atm
partial pressure of water = total pressure x mole fraction of water
= 21 x 5 / 8
= 13.125 atm