Chlorine gas is collected in a gas collecting tube above water. The gas is at 20oC and the total pressure in the tube is 755 mmHg. What is the pressure (in mmHg) of chlorine gas in the tube?
Ptotal = pCl2 + pH2O
Look in your text for the vapor pressure of H2O at 20 C, substitute that for pH2O in the above and solve for pCl2. By the way, this ignores any loss of Cl2 due to dissolving in the water.
To find the pressure of chlorine gas in the tube, we need to subtract the vapor pressure of water at the given temperature from the total pressure.
Step 1: Determine the vapor pressure of water at 20°C.
The vapor pressure of water increases with temperature. You can find a table or use an online resource to look up the vapor pressure of water at 20°C, which is approximately 17.5 mmHg.
Step 2: Subtract the vapor pressure of water from the total pressure.
Pressure of chlorine gas = Total pressure - Vapor pressure of water
Pressure of chlorine gas = 755 mmHg - 17.5 mmHg
Pressure of chlorine gas ≈ 737.5 mmHg
Therefore, the pressure of chlorine gas in the tube is approximately 737.5 mmHg.