GAS ANALYSIS OF NITRITE LABORATORY DISCUSSION

1
GAS ANALYSIS OF NITRITE LABORATORY
DISCUSSION NO2-(aq) H (aq) NH2SO3- (aq) ?
N2(g) HSO4- (aq) H2O(l) Ptot P of N2 P
of H2O SCHEDULE WEEK 1 (Learn
technique) Experiment set-up (leak tests,
determining amount of sample) First runs with
unknown nitrite sample Estimate precision of
results (5 successive runs agree ?V(N2)/msmpl
1) WEEK 2 (Apply technique) Do runs until
precision achieved. Boil 1L of deionized water
for 10 minutes, allow to cool without agitation,
then transfer to 1 L bottle. CO2 free water for
use in preparing NaOH solution for next
experiment. Report due next day.
2

• SAMPLE PRECAUTIONS
• Unknown from stock desiccator
• Transfer to transport desiccator
• Write down sample number
• Weigh only 1 sample at a time
• Use gelatin capsules
• Return unknown vials to stock desiccator at end
  of period
• Estimate size of unknown
• 70 NaNO2
• 730 torr, 295K, 35 mL

3
Keys to Procedure!!!

• Before connecting the Erlenmeyer with the sample,
  raise leveling bulb until levels equalize with
  the buret reading near 0 mL and only 2-3 cm of
  water showing in the leveling bulb.
• Connect the Erlenmeyer carefully but firmly.
• Adjust buret and bulb water levels until they are
  the same. Read buret volume.
• Measure the temperature of the bath and the
  temperature of air near the top of the buret (for
  PV nRT). Make sure thermometer is dry for the
  air measurement.
• Lower leveling bulb before starting reaction.

4

• THINGS TO REMEMBER
• Measure barometric pressure one time each week.
  Barometer located near ovens.
• Before connecting Erlenmeyer, adjust leveling
  bulb so that buret is near 0 mL
• 
  and leveling bulb is only 2-3 cm full
• Only read volume when buret level even with
  leveling bulb level
• If bath ?T gt 0.1ºC at end of run, use ice chips
  to equalize temperature before
• 
  reading
  final volume
• Adjust mass sample to achieve approximately 35
  mL change in volume
• At days end, turn in "kit", replace transfer
  desiccator, put unknown vial storage
  
• 
  
  desiccator
• In write-up, use v. p. of water at your T to
  subtract water P from total P

5
CHANGES FROM LAB MANUAL Step 4 Add sulfamic
acid and then the capsule. Shake periodically.
The capsule does not dissolve immediately. Step
5 Measure T of water in the bath and
T of air near the buret (with dry
thermometer!!!) Use bath T to determine v. p. of
water. Use air T in PVnRT to determine
moles N2 from PN2
6
WEEK 2 Do runs until precision achieved.
Boil 1L of deionized water for 10 minutes w/
boiling chips Allow to cool without
agitation, then transfer to 1 L bottle. CO2
free water for use in preparing NaOH solution for
next experiment.

• .

7
Cooling StorageLab assistant add 4.05 mL of
50 NaOH

• Water has been dyed for viewing purposes.