Final answer:
The pressure of the dry CO₂ collected over water at a temperature of 23.0°C, with a total observed pressure of 799 torr, is 777.9 torr after subtracting the vapor pressure of water (21.1 torr). The correct option is b).
Step-by-step explanation:
To find the pressure of the dry gas CO₂ when collected over water, we must subtract the vapor pressure of water from the total observed pressure. The vapor pressure at 23.0°C is given as 21.1 torr. Thus, the pressure of the dry CO₂ is calculated as follows:
Total observed pressure of CO₂ + water vapor = 799 torr
Vapor pressure of water at 23.0°C = 21.1 torr
Pressure of dry CO₂ = Total observed pressure - Vapor pressure of water
Pressure of dry CO₂ = 799 torr - 21.1 torr = 777.9 torr
The pressure of the dry CO₂ collected over water at a temperature of 23.0°C is 777.9 torr. Option b) is the correct one.