Question

The volume of the nitrogen gas is 125ml atmospheric pressure is 763mm Hg Water temperature is 24 degrees Celcius. The water level inside the eudiometer is the same as the level of water in the beaker.

Calculate the pressure of the dry nitrogen gas.

PH2=Ptotal-PH2O
PH2=763 mm Hg - ????? What is the PH2O. Please help.

Answer 1

Look in your text/notes or on the web. The vapor pressure of H2O at various temperatures will be listed in the table. That is the pressure of the water. An easy rule of thumb when tables are not available (but you can find a table easily) is that in the range of 20-25 C the vapor pressure of H2O in mm Hg is very close to the same as the temperature in degrees C. So it will be close to 24 mm Hg. By the way, note the correct spelling of celsius.