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Oxygen from Hydrogen PeroxideA Safe Molar Volume Molar Mass
ExperimentJohn H. Bedenbaugh, Angela 0 Bedenbaugh, and Thomas S.
HeardUniversity of Southern Mississippi, Hattiesburg, MS 39406
Th e manganese dioxide-catalyzed t hermal decompositionof
potassium chlorate t o produce oxygen is t he classic
molarvolume-molar mass experiment th at has been found incountless
general chemistry laboratory textbooks for de-cades. However, it is
a procedure that is falling into disre-pute. T he potential hazards
inherent in this preparation ofoxygen have been listed I ) and
reports of explosions occur-ring during this experiment continue to
m ount (2).By directsuggestion (3)or implication 4) teache rs are
being advisednot to incorporate this procedure into their program
of ex-periments. unfo rtunately, teachers will find only a very
lim-ited number of experiments from which to choose a suhsti-tute
nrocedure that will accomolish the same instructionalobjectives
(5).
Convinced of the hazard of usina potassium chlorate, we-wanted t
o develop a specific replacement procedure (one inwhich a reactant
on decomposition would yield oxygen gasquantitatively) for use by
students in determining molarvolume or molar mass. We sought a
method that would besimple, rapid, inexpensive, an d in which we
could use locallyavailable chemicals.In 1926 Wikoff and Brown
6)published a procedure forthe qualitative preparation of oxygen
that is rarely citedtoday. A cake of compressed bakers' yeast was
mixed withwater to give a uniform suspension. When a 3% solution
ofhvdroeen neroxide was added t o the susoension, a
vigorous.evolution of oxygen occurred. Bakers' yeast is
exceptfonallyrich in t he enzvme. catalase, which catalyzes th e
decomposi-tion of hydrogen to produce oxygen and water.
2H,0, H,O O2Wikoff and Brown vrovosed t he reaction as a simple,
inex-.pensive way t o prepare oxygen, and also suggested an ad
ap-tation oftheex verime nr toas tud y of th e rate of
liherationofoxygen. ~o w ei er ,hey pointed out th at t he yield of
oxygenfrom hydrogen peroxide via this route was not quanti tative
,hu t they did not explain why. Years later Alyea included a
nupdated version of this reaction among several methods ofpreparing
oxygen 7). He used active dry yeast powder in-stead of moist yeast
cake. Much more recently George an dJohnson developed a procedure
using dry yeast and 3% hy-drogen peroxide for the safe, simple
production of oxygen foruse by elementary school children
8).Because the decomposition of hydrogen peroxide usingcomoressed
veast cake had been reported to be nonquanti ta-tive;we decided to
determine experimentally whither thereaction involving dry yeast
powder is quantitative. I n orderto do that, however, it was
necessary to develop a method forintroducing the yeast into the
hydrogen peroxide solution ina closed system so that the oxygen
evolved could be mea-sured. We sought a simple method appropriate
for use bystudents.rocedure
Titration of Aqueous Hydrogen Peroxide with StandardPotassium
Permanqanate
We wanted to determine accurately the concentration of the
com-mercially available 3% hydrogen peroxide to he used.
Severalsamples (approximately 2.4 g each) were taken from a bottle
of
expanded view ofg s generation system
Gas generation system and gas collection apparatus
hydrogen peroxide purchased at a local store, weighed exactly,
ti-trated with standard potassium permanganate, and the results
wereaveraged to determine the concentration to two decimal
places.The procedure (using the data from one of the
determinations)follows.A 2.3996-g sample of 3% hydrogen peroxide
solution wasweighed into a 250-mL Erlenmeyer flask Then 100 mL of 1
Msulfuricacid was added, and the solution was titrated with
commer-cia1 standard potassium permanganate (0.1005-0.0995 N
usingmagnetic stirring. The volume of permanganate solution used
was41.30 mL. The actual concentration of that particular sample
afhydrogen peroxide solution was thus determined to he
2.93%.Catalytic Decomposition of Hydrogen PeroxideTo Produce
Oxygen
We used essentially the same type of gas collection apparatus
asthat described by Peck, Irgolic, and O'Connor 5) ut developed
thegas generationsystem illustrated in the figure. The pencil
should becylindrical (circular base). It is critical that there be
a good matchbetween the holes in the stopper and the diameter of
the pencil.Holes may have to he drilled in solid stoppers on site
to achieve thefit necessary for easy movement of the pencil through
the stopper.Prior to insertion of the ruhher stopper assembly into
the testtube, the lower 2 cm of the round pencil was coated with
petroleumjelly (Vaseline).Then dry active yeast powder was
sprinkled on thecoated end of the pencil, which was tapped several
times to dislodgeany yeast particles not adhering well to the
hydrocarhon coating.The stopper assembly was then inserted
carefully so as not todislodge the yeast) into the mouth of the
test tube into whichapproximately 4.00 g of 3% hydrogen peroxide
solution had beenweighed.Volume 65 Number 5 May 1988 455
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The gas collection apparatus, filled with tap water that had
beenleft overnight in a container to come to room temperature,
wasconnected with a 60-cm length of flexible tubing to the gas
genera-tion system, and the closed system was checked for air leaks
byraising and lowering the leveling bulb. After it was determined
thatthe system was gas-tight, he tubing was momentarily
disconnectedat the top of the buret, and the level of water in the
buret wasadjusted to approximately1cm above the zero mark by moving
theleveling bulb. Then the free end of the tubing was
reattached,thereby closing the system again, and the water level in
the huretdropped to slightly below the zero mark. After again
adjusting theleveling bulb until its water level matched that of
the buret, thewater level in the buret was read and recorded. Also
recorded werethe room temperature and barometric pressure.Reaction
was initiated by pushing the pencil into the solutionuntil the top
mark on the pencil coincided with the top of thestopper.
(Lubrication of this upper area of the pencil facilitated
itsmovement through the stopper.) The yeast adhering to the
petro-leum jelly was thus brought into contact with hydrogen
peroxide,which decomposed to give a smooth, steady evolution of
oxygen. Toinsure good mixing the test tube was shaken gently
several times.When the water level became stationary, he reaction
was complete.The test tube was then shaken a final time, the water
levels in theburet and bulb matchedaeain. and thevolumeofwater
remainine in.the buret read and recorded. Reaction was complete in
less thanthree minutes. Only about 15 minutes was required for all
opera-tions involved in each determination.A volume correction
(tohe subtracted from the volume of oxygenmeasured) is required to
compensate for the increase in gas volumeproduced by the insertion
of the pencil into the liquid. This correc-tion can be determined
experimentally by simply measuring theamount of water displaced in
the buret when the pencil is pushedthe measured distance into the
empty test tube with the entiresystem closed. Alternatively,knowing
the diameter of the pencil andthe additional length (in
centimeters) of the pencil to be inserted,the volume correction can
be calculated from the formula: u = r r z hwhere h is the distance
from mark to mark and, therefore, thedistance of the increased
intrusion of the pencil into the closedsystem.We assumed no loss of
oxygen generated due to solubility inwater. This appears reasonable
since the tap water used in themeasuring apparatus had not been
degassed.
Data ObtainedFollowing the standardization of t he hydrogen
peroxidesolution with Dermanganate, the procedure described
wascarried out se\:en tnn& to get the data we report. A samplem
a s of approximately 4 g was used to produce a volmne ofoxwen 110
45 ml.1 that would utilipe most ofthecaoacitvofn ~ ~t he bu r e t .
~ now i ' n~he volume of oxygen collected overwater at room temner
ature and nressure from a aiven massof hydrogen peroxide solutinn,
t he \ ,olume of oxvgen at 5 1 1w3s calr~datrd. his value was
romr~aredwith the throrrr i-cal yield of oxygen a t S T P from
the.given mass of hydrogenperoxide solution, and t he error was
calculated.Errors ranged from 0.18-3.13%) th e average error
was1.80%.We concluded that, within experimental error, thereaction
is quantitative.
Three Experiments PossibleTh e ~ro ce du re escribed is the
basis of three experimentsth at may be done by student s to
determine: (1) molar vol-ume of oxygen, (2) molar mass of hydrogen
peroxide, (3)concentration of hydrogen peroxide i n aqueous
solutions.A student can make any of these three determinationsafter
measurine the volume of oxvaen obtained from theexperimental
procedure and n oti ng tha t two moles of hydro-een oeroxide vield
one mole of oxygen (from the equation forih e ieaction):Th e data
obtained in t he laboratory are: mass of the hy -drogen peroxide
solution; room temperature and pressure;and initial and final huret
readings. From these readings,after application of the correction
factor for pencil insertion,
one can determine the volume of oxygen collected over waterat
room temperature and pressure. After calculating thepartial
pressure of the oxygen produced in the system, thevolume of oxygen
a t STP is determined via the usual gas-lawcalculations.To determi
ne either the molar volume of oxygen or t hemolar mass of hydrogen
peroxide, obviously the studentmust be given (or must first
determine) the concentration ofthe aqueous hydrogen peroxide
solution used in order tocalculate them ass of hydrogen peroxide
from th e mass of thehydrogen peroxide solution.The basic equations
needed for these experiments are(1) Molar Volume of Oxygen
g H O 68.02 g H OmL 0, (STP) x
[molar mass of Hz02 = 34.01 glmol](2) M d ar Mass o Hydrogen
Peroxide
g H AmL 0, (STP) 11,200 mL 0
(3) Concentration of Hydrogen Peroxide in an
AqueousSolution34.01 gH O (x)(gH O soln.)
=11,200 mL 0, mL 0, (STP)Comments
This experiment is inherently safe because no heat is in-volved
and no hazardous chemicals are used. Moreover, aneffort has been
made to make every aspect of t he entireprocedure safe. Th us a
pencil is used t o introduce the yeastto avoid cuts arising from
pushing a glass rod through th ehole in t he rubber stopper. Also
medicine dropper pipets areused rather than glass tubing because
glass cutti ng is avoid-ed and insertion into the holes of the
rubber stoppers ismade easier because of the tapered ends of the
pipets. Inpreparing unknowns for students to use in
determiningconcentration of solutions, it is suggested th at
various dilu -tions of 3% hydrogen peroxide he prepared ra ther t
han pur-chasing more concentrated solutions that are not
readilyavailable and that may be hazardous when used in
thisprocedure.The short reaction time makes it quite feasible for
thestudent to conduct the experimental procedure three timesduring
a one-hour laboratory period to get an average valueand a standard
deviation.Thi s is an exceptionally economical experiment. T he
costof consumable supplies is only $0.015 per reaction. T hu s
20students could each perform the experiment three times fora tota
l cost of $0.90 for consumables.Summary
Dry yeast-induced decomposition of dilute aqueous hy-drogen
peroxide t o produce oxygen is a safe, simple, econom-ical
replacement for thermal decomposition of potassiumchlorate in molar
volume and molar mass experiments.Moreover, the hydrogen peroxide
decomposition~procedurecan he the basis of an experiment in which
the concentrationof hydrogen peroxide solutions is determined
.Literature Cited
oiPublic Inatructian: Raleigh NC4. Flinn 985
Cololog/Re/ermc~Monuai linn Scientific Batavia. IL; p 1036 Peck L.:
Irdic. K.:O'Connor.R.J. Chem E d u c 1980.57.517.
456 Journal of Chemical Education
