A student investigated the rate of decomposition of a hydrogen peroxide (H₂O₂) solution using manganese dioxide (MnO₂) as a catalyst - Leaving Cert Chemistry - Question 3 - 2018
Question 3
A student investigated the rate of decomposition of a hydrogen peroxide (H₂O₂) solution using manganese dioxide (MnO₂) as a catalyst. The equation for the reaction i... show full transcript
Worked Solution & Example Answer:A student investigated the rate of decomposition of a hydrogen peroxide (H₂O₂) solution using manganese dioxide (MnO₂) as a catalyst - Leaving Cert Chemistry - Question 3 - 2018
Step 1
Name a suitable piece of apparatus to measure out 5 cm³ of hydrogen peroxide solution A.
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Answer
A suitable piece of apparatus to measure 5 cm³ of hydrogen peroxide solution A is a graduated cylinder, graduated dropper, pipette, syringe, or burette.
Step 2
Describe the appearance of the MnO₂ catalyst.
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Answer
The appearance of the manganese dioxide (MnO₂) catalyst is typically described as a black or dark brown solid powder.
Step 3
Complete your diagram and label it to show: i) the location of the catalyst just before the reaction is started.
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Answer
In the diagram, label the position of the MnO₂ catalyst inside the small test-tube flask B, situated in the conical flask A prior to the start of the reaction.
Step 4
Complete your diagram and label it to show: ii) how the oxygen gas can be collected and its volume measured at intervals over several minutes.
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Answer
Label the graduated gas syringe Y connected by flexible tubing to the conical flask, showing where the oxygen gas will be collected and its volume can be measured.
Step 5
Plot a graph (on graph paper) of volume of O₂ (y-axis) versus time.
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Answer
On the graph, plot the volume of oxygen gas (in cm³) on the y-axis against time (in minutes) on the x-axis. Ensure to label both axes correctly with units.
Step 6
Why does the rate of this reaction slow down as the minutes go by?
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Answer
The rate of the reaction slows down over time due to the depletion of hydrogen peroxide (H₂O₂) concentration as it gets consumed in the reaction, leading to a decrease in the frequency of effective collisions.
Step 7
Use your graph to find the volume of gas collected in the first 2.5 minutes.
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Answer
From the graph, determine the volume of oxygen gas collected at the 2.5 minutes mark to find the corresponding volume.
Step 8
In the same sheet of graph paper sketch the curve you would expect to plot if the experiment were repeated using 2.5 cm³ of hydrogen peroxide solution A diluted to 25 cm³.
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Answer
Sketch a curve on the graph representing a faster reaction due to the increased concentration of hydrogen peroxide, which should produce more oxygen gas in the initial minutes compared to the previous graph.
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