Answer:
PO2 = 776.2 mmHg
Step-by-step explanation:
When it comes to gases collected on water, Dalton's law is of the utmost importance:
∴ P*H2O: vapor pressure
⇒ P*H2O (25°C) = 23.8 mmHg
∴ Patm = 800 mmHg
⇒ PO2 = 800 mmHg - 23.8 mmHg
⇒ PO2 = 776.2 mmHg