In an investigation into the decomposition of a hydrogen peroxide solution, using a manganese(IV) oxide catalyst, the volume of oxygen produced was monitored with time - Leaving Cert Chemistry - Question 3 - 2016
Question 3
In an investigation into the decomposition of a hydrogen peroxide solution, using a manganese(IV) oxide catalyst, the volume of oxygen produced was monitored with ti... show full transcript
Worked Solution & Example Answer:In an investigation into the decomposition of a hydrogen peroxide solution, using a manganese(IV) oxide catalyst, the volume of oxygen produced was monitored with time - Leaving Cert Chemistry - Question 3 - 2016
Step 1
Draw a labelled diagram of an apparatus that could have been used in either run of this investigation.
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Answer
A labelled diagram should include:
A conical flask or reaction vessel containing hydrogen peroxide.
A funnel or a dropping funnel (if necessary).
A manganese(IV) oxide catalyst inside the flask.
A gas collection method, such as a delivery tube leading to a graduated gas syringe or water displacement method (using a graduated cylinder). Each part must be clearly identified with labels.
Step 2
On the same sheet of graph paper, using a common set of axes, plot a graph of volume of oxygen produced versus time for each run.
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The graph should have:
X-axis labeled 'Time (minutes)' with appropriate intervals.
Y-axis labeled 'Volume of Oxygen (cm³)' with proper scaling.
Plotted points for both Run A and Run B.
Smoothing curves that show the trends for both runs appropriately.
Step 3
Calculate the instantaneous rate of reaction (in cm³ O₂ per minute) for run A at 4.0 minutes.
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Answer
To calculate the instantaneous rate at 4.0 minutes, find the volume of oxygen produced at slightly before and after that time:
At 3.0 minutes: 51 cm³
At 5.0 minutes: 72 cm³
Change in volume = 72 cm³ - 51 cm³ = 21 cm³
Change in time = 5.0 minutes - 3.0 minutes = 2 minutes
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Answer
Run A reached completion first, as it produced a total volume of oxygen (82 cm³) within 8 minutes, whereas Run B took longer to reach the same volume.
Step 5
(ii) had the slower initial rate?
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Run B had the slower initial rate. The rate can be inferred from the volume change over the first minute, with Run B producing only 16 cm³ compared to Run A's 25 cm³.
Step 6
What type of catalysis was involved in the reactions?
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The reaction involves heterogeneous catalysis, as manganese(IV) oxide acts as a solid catalyst facilitating the decomposition of a liquid hydrogen peroxide solution.
Step 7
Suggest how the catalyst used in run A may have differed from that used in run B to account for your answers to parts (d) and (e).
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The catalyst in Run A may have had a greater surface area or different particle size compared to Run B, allowing for more active sites for the reaction to occur. This could lead to a faster reaction rate and quicker completion in Run A.
Step 8
What chemical hazard is indicated by the pictograms shown for hydrogen peroxide?
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The pictograms indicate that hydrogen peroxide is a strong oxidizing agent and poses an explosion hazard in the presence of organic materials.
Step 9
(ii) manganese(IV) oxide?
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Manganese(IV) oxide is indicated to be harmful and may cause irritation, and it is also a substance that can create hazardous reactions under certain conditions.
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