A student uses a eudiometer tube to collect oxygen gas over water where the temperature is 22 ºC. What is the pressure of the oxygen gas (mm Hg) if the air pressure in the lab is 735 mm Hg?
Ptotal = pO2 + pH2O
Ptotal = 735
PH2O==look up the vapor pressure of H2O at 22 C. Calculate pO2.
To determine the pressure of the oxygen gas, we need to consider the partial pressure of the gas collected inside the eudiometer tube and the pressure exerted by the water vapor.
The total pressure in the eudiometer tube is a combination of the pressure of the collected oxygen gas and the pressure of the water vapor. In this case, we know the air pressure in the lab, which is 735 mm Hg, and the temperature of the water, which is 22 ºC.
To calculate the pressure of the oxygen gas, we'll use Dalton's Law of Partial Pressures, which states that the total pressure of a gas mixture is equal to the sum of the partial pressures of each gas.
First, we need to determine the pressure of the water vapor at 22 ºC. We can use vapor pressure tables to find this value. At 22 ºC, the vapor pressure of water is approximately 19.8 mm Hg.
Now we can calculate the pressure of the oxygen gas. Since the total pressure is the sum of the partial pressures, we can subtract the vapor pressure of water from the total air pressure:
Pressure of oxygen gas = Total pressure - Vapor pressure of water
= 735 mm Hg - 19.8 mm Hg
= 715.2 mm Hg
Therefore, the pressure of the oxygen gas inside the eudiometer tube is approximately 715.2 mm Hg.