6.1 - Rate of Production of Oxygen from Hydrogen Peroxide

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Experiment Summary

In this experiment, the rate of production of oxygen ( $O₂$ ) is monitored by decomposing hydrogen peroxide ( $H₂O₂$ ) using manganese(IV) oxide ( $MnO₂$ ) as a catalyst. The decomposition of hydrogen peroxide produces water and oxygen.

2\text{H}_2\text{O}_2 \rightarrow 2\text{H}_2\text{O} + \text{O}_2

The oxygen produced is collected over water or measured using a gas syringe. The volume of oxygen is recorded at regular intervals, allowing the rate of the reaction to be determined.

Materials and Apparatus Required

Chemicals

20-volume hydrogen peroxide (H₂O₂)
Powdered manganese(IV) oxide (MnO₂)
Water

Apparatus

100 cm³ graduated cylinder or gas syringe
Beehive shelf and large trough (for water displacement method)
Conical flask with a stopper and delivery tube
Stop-clock
Small test tube and thread
Teat pipette

Safety Precautions

Wear safety glasses at all times.
Hydrogen peroxide is corrosive and can cause burns. Avoid contact with skin and eyes.
Manganese(IV) oxide dust is harmful if inhaled and can irritate the eyes and skin. Handle with care, and avoid generating dust.
Clean up spills immediately and dispose of waste properly as outlined below.

Method

Method 1: Using an Inverted Graduated Cylinder

Measure 5 cm³ of hydrogen peroxide and dilute it to 50 cm³ with water in a conical flask.
Weigh 0.5 g of manganese(IV) oxide into a small test tube.
Suspend the test tube containing $MnO₂$ in the conical flask using a thread, ensuring that the $MnO₂$ does not come into contact with the $H₂O₂$ yet.
Fill a trough with water and invert a 100 cm³ graduated cylinder over a beehive shelf filled with water.
Set up the delivery tube to collect oxygen produced in the graduated cylinder by water displacement.
Loosen the stopper and shake the conical flask vigorously to allow the $MnO₂$ to mix with the $H₂O₂$ . Start the stop-clock immediately.
Record the volume of oxygen produced in the graduated cylinder every 30 seconds.

Method 2: Using a Gas Syringe

Measure 8 cm³ of hydrogen peroxide and dilute it to 50 cm³ with water in a conical flask.
Weigh 0.5 g of manganese(IV) oxide and suspend it in a small test tube using a thread as described above.
Set up the gas syringe and connect the delivery tube to the conical flask.
Loosen the stopper and shake the flask to allow the $MnO₂$ to mix with the $H₂O₂$ . Start the stop-clock.
Record the volume of oxygen produced in the gas syringe every 60 seconds.

Results

Time (s)	Volume of Oxygen (cm³)
0	0
60	25
120	36
180	45
240	53
300	60
360	66
420	70
480	75
540	78
600	82
660	85

Example Questions with Answers

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Q1: Why is the slope of the graph steepest at the beginning of the reaction?

The reaction rate is proportional to the concentration of hydrogen peroxide.

At the start, the concentration is at its highest, so the rate of oxygen production is the fastest, resulting in the steepest slope.

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Q2: How can you tell when the reaction is complete?

The reaction is complete when the graph levels off, indicating no more oxygen is being produced.

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Q3: What would happen if the amount of manganese(IV) oxide used was doubled?

The rate of reaction would increase, leading to a steeper slope on the graph.

However, the total volume of oxygen produced would remain the same, as the catalyst only speeds up the reaction, not the amount of product.

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Q4: What effect would doubling the concentration of hydrogen peroxide have on the results?

Doubling the concentration would double the total volume of oxygen produced and increase the reaction rate, resulting in a steeper slope and a higher final volume of gas.

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Q5: Why is it important to take readings at eye level when measuring the volume of gas produced?

Taking readings at eye level avoids parallax error, ensuring accurate measurement of the gas volume.

- Rate of Production of Oxygen from Hydrogen Peroxide Simplified Revision Notes for Leaving Cert Chemistry

6.1 - Rate of Production of Oxygen from Hydrogen Peroxide

Experiment Summary

Materials and Apparatus Required

Chemicals

Apparatus

Safety Precautions

Method

Method 1: Using an Inverted Graduated Cylinder

Method 2: Using a Gas Syringe

Results

Example Questions with Answers

Q1: Why is the slope of the graph steepest at the beginning of the reaction?

Q2: How can you tell when the reaction is complete?

Q3: What would happen if the amount of manganese(IV) oxide used was doubled?

Q4: What effect would doubling the concentration of hydrogen peroxide have on the results?

Q5: Why is it important to take readings at eye level when measuring the volume of gas produced?

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