O2 Lab

The oxygen lab uses most of what we have learned this year.

  1. Naming
  2. Balancing a decomposition reaction
  3. Mass-volume Stoichiometry problem to find gas volume at STP and dry conditions .
  4. Combined gas law problem with water vapor correction to find the actual volume of gas generated.

Remember a mass-volume stoichiometry problem can be solved with a 4 step factor label problem.

grams of known 1 mole of known  __ moles of unknown 22.4 L of unknown **
  1 GFW of known  __ moles of known 1 mole of unknown

**22.4 L gas per mole is only true at STP and dry conditions

The third set of boxes comes from the balanced reaction. (Use the coefficients or the big number in front of the chemical)

This will be the V1 T1 and P1 for a combo  gas law problem. V1 is your answer, T1 is 273K and P1 is 760 mm Hg (STP)

V2 is what we are solving for.

T2 will usually be room temperature.

P2 is usually room pressure minus the water vapor pressure at T2. Use the corrected P2 to make the water correction.

In our classroom in Carson City, the room barometer usually reads around 850 to 855 hPa. Unfortunately it's not in mm Hg.
855 hPa 760 mm Hg.
  1013 hPa

 = 642 mm Hg - water vapor pressure.   (Usually 15 to 20 mm Hg depending on temp of water).