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This question is about three different reactions, P, Q and R - Edexcel - GCSE Chemistry - Question 6 - 2016 - Paper 1
Question 6
This question is about three different reactions, P, Q and R. As the reactions are carried out, the initial and final temperatures are recorded. | reaction | initi... show full transcript
Worked Solution & Example Answer:This question is about three different reactions, P, Q and R - Edexcel - GCSE Chemistry - Question 6 - 2016 - Paper 1
Step 1
Explain which of these reactions, P, Q or R is exothermic.
Answer
To determine which reaction is exothermic, we evaluate the change in temperature for each reaction. An exothermic reaction is characterized by a decrease in temperature of the surroundings, indicating that energy is released.
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Reaction P:
- Initial temperature: 16 °C
- Final temperature: 12 °C
- Temperature change: 16 °C - 12 °C = 4 °C decrease (Exothermic)
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Reaction Q:
- Initial temperature: 15 °C
- Final temperature: 34 °C
- Temperature change: 34 °C - 15 °C = 19 °C increase (Endothermic)
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Reaction R:
- Initial temperature: 17 °C
- Final temperature: 17 °C
- Temperature change: 17 °C - 17 °C = 0 °C (No change)
Based on the above analysis, only Reaction P shows a decrease in temperature, which indicates that it is exothermic.
Step 2
Place a cross in a circle on the graph to show where the reaction is at its fastest rate.
Answer
To indicate the fastest rate of the reaction on the graph, we would cross at the steepest part of the curve. This corresponds to the point where the volume of hydrogen gas produced increases most rapidly, typically at the beginning of the reaction.
Step 3
On the graph, sketch a line to show the results you would expect in this case.
Answer
When hydrochloric acid is more dilute, the reaction will happen more slowly. Thus, the line should rise more gradually compared to the original graph, showing a slower rate of gas production over the same period.
Step 4
Explain why powdered coal burns in air at a faster rate than lumps of coal.
Answer
Powdered coal burns faster than lumps of coal primarily due to its increased surface area. A larger surface area allows more particles to come into contact with oxygen in the air, facilitating a quicker combustion reaction. Additionally, finer particles heat up more quickly, enhancing the rate of burning.
Step 5
Using hydrogen peroxide solution and manganese(IV) oxide, describe experiments to show that manganese(IV) oxide has these properties when used as a catalyst in this reaction.
Answer
To demonstrate the catalytic properties of manganese(IV) oxide in the decomposition of hydrogen peroxide, perform the following experiment:
- Set up the apparatus: In a conical flask, add a measured volume of hydrogen peroxide solution.
- Add manganese(IV) oxide: Introduce a small amount of manganese(IV) oxide to the flask.
- Observe the reaction: Notice that the reaction occurs rapidly, producing gas (oxygen) and bubbles. Measure the volume of oxygen gas produced over a specific time.
- Repeat with no catalyst: Conduct the same experiment without the manganese(IV) oxide to compare the rate. The reaction should occur much slower, demonstrating that manganese(IV) oxide increases the rate of reaction.
- Confirm unchanged mass: After the reaction, weigh the manganese(IV) oxide. The mass should be nearly unchanged, confirming that it does not lose mass during the reaction and operates as a catalyst.