Investigate how the concentration of a
hydrogen peroxide solution affects the
speed at which it decomposes to produce
oxygen gas
Introduction
Background research outlined and
referenced
• When I first read the investigation, I referred to the
chapter on oxygen in my textbook to re-familiarise myself
with the topic.
• I made note of relevant facts, such as, the properties of
Oxygen, and the technique used to prepare oxygen gas
by decomposing hydrogen peroxide.
Background research outlined and
referenced
• I then, referred to my brother’s Leaving Cert. Chemistry
Textbook, (Declan Kennedy,Chemistry Alive) for
additional information and direction on how to approach
the investigation, particularly making note of ideal H2O2
concentration used. (20 volumes)
• From my textbook, I also reviewed the affect the catalyst
Manganese Dioxide has on the breaking down of H2O2
Background research outlined and
referenced
• My teacher also helped by facilitating a discussion in
class and highlighting safety precautions necessary
when dealing with H2O2.. I found out that it is corrosive
and an oxidiser, therefore safety glasses, lab coat and
vigilance are a high priority.
Investigation is stated as a problem
statement
“ To examine that the rate at which oxygen
gas is produced depends on the
concentration of hydrogen peroxide used”
Preparation & Planning
Identification of variables
• Independent variable:
The concentration of hydrogen peroxide
• Dependent variable:
Volume of oxygen gas produced in set time, 30 sec, 60 sec.
• Fixed Variables:
Mass of manganese dioxide used
Volume of hydrogen peroxide used
Same equipment /glassware used
A Fair Test
• To ensure a fair test, the fixed variables must be
constant.
• Only the independent variable must change.
• This guarantees that the rate of oxygen gas
produced, depends on the concentration of
hydrogen peroxide used.
Resource List
• Various concentrations of 20 volume hydrogen peroxide
(20%, 40%, 60%, 80%, 100%)
• Manganese dioxide
• Water
• Dropping syringe
• Conical flask
• Rubber bung with 2 holes for necessary tubing
• Waterbath
• Beehive shelf
• Stop watch
• Graduated cylinder for gas collection
Resource List
•
•
•
•
•
•
•
Balance
Waterbath
Beehive shelf
Stop watch
Special test tubes for gas collection
Safety glasses
Lab coat
Plan adequate to test problem
statement
• In order to plan the procedure fully, a trial run
must be carried out.
• The trial run consisted of running through the
procedure to prepare oxygen gas using 100%
concentration of H2O2, and then repeated at 10%.
• Firstly, a stop watch was used to time how long it
takes to collect 1 full test tube of oxygen gas.
Plan adequate to test problem
statement
• The test was ran again( using each of both
100% and 10% concentrations, respectively).
• This time looking at how much volume of oxygen
was collected in 30 seconds
• From carrying out the experiment both ways, it
was decided to proceed using the latter method,
i.e. monitoring the volume of oxygen gas
produced in 30 seconds.
Plan adequate to test problem
statement
• It was decided that timing would begin as soon
as first oxygen bubble reached the water
surface.
• Each time method was carried out, it was
important to ensure 1g of manganese dioxide
was constant each time. ( this was in
accordance to recommended mass used in
textbook)
Procedure
Procedure listed in clear logical
order
• Personal Safety Equipment was put on
• All reagents and apparatus was organised on
bench
• The standard 20 volume hydrogen peroxide
solution, was labelled 100% concentration.
• Further dilutions of 20%, 40%, 60%, and 80%
were made up from the stock 100%.
Procedure listed in clear logical
order
• For example, the 20% solution was made by
measuring 20mls of hydrogen peroxide in a
graduated cylinder and mixing it thoroughly with
80mls of water. (The other concentrations were
measured using the same procedure.)
Procedure for 20% concentration of hydrogen peroxide
• 30 mls of hydrogen peroxide was measured
and placed in the dropping syringe
Procedure listed in clear logical
order
• 1g of manganese dioxide, weighed on a
balance, was added to the conical flask.
• Apparatus was set up as shown in diagram with
graduated cylinder inverted in trough for
collection of oxygen gas.
• Hydrogen peroxide was released from dropping
syringe into conical flask.
Procedure listed in clear logical
order
• Once first gas bubble reached surface of water,
stop watch was started and let run for 30
seconds.
• Immediately at 30 seconds, the Volume of gas
produced was easily read from graduated
cylinder.
Procedure listed in clear logical
order
• This was repeated twice for the 20 % solution, to
ensure accuracy.
• Procedure was repeated for 40%, 60%, 80%
and 100% concentrations. Again carried three
times in total.
Safety
• Personal Safety equipment was worn .
• Care was taken when handling glassware, and
in particular when handling manganese dioxide
(irritant) and hydrogen dioxide (corrosive ,
oxidiser)
Recorded Data
H2O2 Concentration
Volume Trial 1(ml)
Volume trial 2(ml)
Average Volume (ml)
20%
34ml
36ml
35ml
40%
47ml
44ml
45.5ml
60%
66ml
66ml
66ml
80%
84.5ml
85ml
84.75ml
100%
96ml
97ml
96.5ml
Labelled Diagram
•
Graph
1.2
1
0.8
0.6
H2O2 Concentration
0.4
0.2
0
35ml
45.5ml
66ml
84.75ml
96.5ml
Calculations/Data Analysis
• The average results were calculated as seen in
the results table.
• This was then used to draw a best fit line as
seen in the graph.
• A wide range of concentrations from 20%100%, were tested in duplicate, which gave a
confirmation of expected results.
Observations
• During my first practice run, I did not close the
tap on the syringe after releasing the hydrogen
peroxide. This could have let some of the
Oxygen escape, therefore affecting results.
• While using the stopwatch, I had to be alert and
quick to start exactly at the first bubble, and read
volume as soon as 30 seconds were over.
Observations
• From carrying out the procedure in repetition, I
can see that the concentration of hydrogen
peroxide determines the rate of oxygen
produced.
Comments on suitability of
procedure
• If more time was allowed, I feel we could have
perfected our technique in both producing the
oxygen and timing the rate at which it was
produced.
• Some factors that may have affected results:
1. When putting the hydrogen peroxide solution
into the burette, the tap was often left open,
spoiling that particular run and wasting the
chemicals.
Comments on suitability of
procedure
2. Air bubbles in the graduated cylinder were a
reoccuring problem, which may have altered the
exact rate of oxygen being produced.
Conclusion
From this investigation, it can be
concluded that the concentration of
hydrogen peroxide greatly affects the
speed at which it decomposes to produce
oxygen gas.