Unit 8 Gas Stoich Lab09hot_ - North High School

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Unit 8 Gas Stoich Lab09hot_ - North High School Powered By Docstoc
					       Gas Stoichiometry
 Purpose: Production of oxygen gas
by reacting sodium hypochlorite and
         hydrogen peroxide
 Background:
      Sodium
 hypochlorite, the
 active ingredient
in laundry bleach,
 is also used as a
   disinfectant.
     Background:
     H2O2 has strong
  oxidizing properties.
   It is used to bleach
 paper. It is also diluted
and used as an antiseptic
    and disinfectant.
    The Reaction:
 Sodium hypochlorite
 reacts with hydrogen
peroxide to produce…
…sodium chloride (aq),
water (l) and oxygen (g)

   Write the balanced
equation for the reaction.
NaClO (aq) + H2O2 (aq) 

H2O (l) + NaCl (aq) + O2 (g)


  I know you wrote it yourself. Be sure it’s balanced!
    Materials and Equipment
• 100 ml graduated   • Ring stand
  cylinder           • Test tube clamp
• Rubber stopper     • 250 ml
• Gas tube             Erlenmeyer flask
• Small vial         • Water bath
                     • tweezers
           Procedures
1. Set up a ring stand and test
   tube clamp.

2. Check that the water bath
   drain is clamped, before you
   fill the bath with water.
3. Fill the graduated cylinder with
   water and place in the water
   bath. Invert it and clamp it
   with the test tube clamp.

  *Make sure there is no air in the
  graduated cylinder before you start.
Clamped and ready to go.
4. Mass 3.00 ~ 5.00 grams of
   NaClO and place in a 250 ml
   Erlenmeyer flask.
Mass 3.00 ~ 5.00 grams of H202
         in a small vial.
6. Use tweezers to set the vial
   in the Erlenmeyer flask.
   Don’t let it spill.
7. Seal the Erlenmeyer flask
   with the rubber stopper. Place
   the free end of the gas tube
   into the water bath and into
   the bottom of the graduated
   cylinder.
8. Gently tip the vial over to
   start the chemical reaction.

  (Make sure the resulting gas
  bubbles are being caught in
  the graduated cylinder!)
9. Once the reaction is finished,
   record the height of the water
   above/below the bath height,
   and record the volume of the
   gas produced.
10. Record the atmospheric
  pressure and the room
  temperature.
11. Rinse out your equipment and
  begin trial 2. Repeat steps 1-10.
  Record as trial 2. After
  completing trial 2, do as many
  additional trials as you have
  time. (More points for more
  trials.)
       Sample Data Table Page 1
Remember to show units   Trial 1 Trial 2 T3 T4 T5
Mass NaClO solution
(g)
Mass H2O2 solution
Vol. of O2 collected
Water height above
bath level
Room Pressure
Room Temperature
           Analysis Table Page 1
Analysis              Trial 1 Trial 2 T3 T4 T5
Mass NaClO (6%)
Mass H2O2 (3%)
Height correction
Vapor Pressure H2O
Actual Gas Pressure
Actual Moles of O2
collected
% Yield
  Analysis/Calculation Questions

Begin TRIAL 1
1. Use the concentration
   percentage to find mass of
   NaClO (6%)
2. Find mass of H2O2 (3%)
 Analysis/Calculation Questions (cont.)
3. Check for a limiting reactant:
   Find the moles of oxygen gas
   that could form from the mass of
   NaClO from step 1.
  Find the moles of oxygen gas
  again, using the mass of H2O2
  from step 2. Which is limiting?
Analysis/Calculation Questions (cont.)

4. State the theoretical yield of
   oxygen in moles.

5. Convert the theoretical
   yield of oxygen into mL.
 Analysis/Calculation Questions (cont.)
6. Determine the actual partial
   pressure of oxygen gas
   trapped by accounting for
   both the:
a. water level height difference
b. vapor pressure of water
 Analysis/Calculation Questions (cont.)


7. Use the ideal gas law to
 find the actual yield in
 moles of O2 gas captured.
Analysis/Calculation Questions (cont.)

8. Find the percent yield.
  (Use the actual yield of
  moles captured over the
  theoretical yield of moles
  produced.)
Analysis/Calculation Questions (cont.)

9. Repeat the analysis for
   trial 2 and all other trials.
10. Average the percent
  yield for all trials.
    Concluding Questions

1. Explain why the
   atmospheric pressure of
   the room is not the same
   as the oxygen gas partial
   pressure in the cylinder?
     Concluding Questions

2. How does the room
   temperature affect the lab
   results? Do you think
   room temperature is a
   good number to use?
       Concluding Questions
3. As you began collecting gas,
   were your flask and hose
   empty, full of pure oxygen gas,
   or what?
   Did this affect your results?
   Explain why or why not.
       Concluding Questions
4. Was your percent yield
   higher or lower than the
   yield of the other groups
   around you? Why or why
   not? (You can answer this after
  checking with your neighbors in
  class.)
     Concluding Questions

5. Explain why it was
 important to take an average
 of your trials when coming
 up with your final percent
 yield?
         Last Question!
6. If you were going to do the
   lab again, what procedures
   or conditions would you
   alter or change to help
   increase your percent yield?
   Explain.

				
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