Partial Pressures

To calculate the partial pressures of each of the gasses first determine the P_total. This is the same for everybody because it is the atmospheric pressure of the classroom and is determined from the barometer hanging on the wall. Call someone if you did not write it down. It will be in mm Hg so convert it to atm. Remember that there are 760 mmHg in 1 atm.

The next thing you want to do is calculate the P_H2. You can determine this by taking the number of moles of H₂ you found in the previous problem and plugging it into PV = nRT. Rearranging the equation to solve for P or P_H2. We have done this a few time so you should be able to do this on your own. P_H2 + nRT/V were n is the number of mole you found in the previous problem, T is the temperature in Kelvin, and V is the volume you found in the experiment.

If you now look at what we have calculated, P_H2 and P_total we can now find the P_H2O. This is just a partial pressure problem.

P_total = P1 + P2 + P3 ……. Or P_total = P_H2 + P_H2O. Solve for P_H2O.