Chemistry Depth study question (1 Viewer)

chrstinee

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Could someone give me an outline on how I should answer this question and where the marks are allocated.image.jpg
 

thush@decode

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Given the number of marks allocated to this question - this is likely to be marked "holistically" if it were asked in the real NESA exam.
To get a Band 6-level response (which would be equivalent to 5-6/6 in this question I suspect), you would need to show "an extensive knowledge and understanding of scientific concepts", and "communicate scientific understanding succinctly, logically, and consistently using correct and precise scientific terms" which is just NESA-speak for you need to show you know your stuff and that you can write well.

Questions to ask yourself when asked to "assess" a statement:
  • To what extent is this statement accurate? On this occasion, I'd say this is very accurate - except I would add a small pointer that the catalyst provides a different reaction mechanism/pathway which happens to have a lower activation energy, as opposed to lowering the activation energy of the usual reaction mechanism.
  • What contributes and detracts from the accuracy of this statement? On this occasion, catalysts almost by definition allow the reaction to occur with a lower activation energy. However, as previously explained - there is more to the story than that statement provides.
When answering, you could try this structure:
  • Topic sentence/contention - "This statement is reasonably accurate...."
  • Explanation (pluses and minuses) - "On the one hand..." and "On the other hand/However..."
  • (Diagrams and reference to these diagrams to illustrate your point(s))
  • Final judgement call - "Overall, it is accurate to say that catalysts lower the activation energy - but it is more accurate to say that they provide a different reaction mechanism/pathway which happens to have a lower activation energy."
Ensure you make a final judgement call on this question when answering it.

On a side note - I think this question could be better worded/modified. Depicting the lowering of the activation energy via the Maxwell Boltzmann distribution curve and explaining the relationship between reaction rate and lower activation energies using collision theory does not support the statement that "catalysts lower the action energy" but, rather, merely assume that statement is true and uses it to extrapolate other things (eg. that catalysts can increase reaction rates).
The question as written - could - be reasonable if previous question parts, for example, show data depicting that adding a catalyst without increasing reactant concentration or temperature is shown to increase a reaction rate, and you are expected to deduce that the only way a catalyst could increase the reaction rate is by lowering the activation energy. Was this the case?
 

chrstinee

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Given the number of marks allocated to this question - this is likely to be marked "holistically" if it were asked in the real NESA exam.
To get a Band 6-level response (which would be equivalent to 5-6/6 in this question I suspect), you would need to show "an extensive knowledge and understanding of scientific concepts", and "communicate scientific understanding succinctly, logically, and consistently using correct and precise scientific terms" which is just NESA-speak for you need to show you know your stuff and that you can write well.

Questions to ask yourself when asked to "assess" a statement:
  • To what extent is this statement accurate? On this occasion, I'd say this is very accurate - except I would add a small pointer that the catalyst provides a different reaction mechanism/pathway which happens to have a lower activation energy, as opposed to lowering the activation energy of the usual reaction mechanism.
  • What contributes and detracts from the accuracy of this statement? On this occasion, catalysts almost by definition allow the reaction to occur with a lower activation energy. However, as previously explained - there is more to the story than that statement provides.
When answering, you could try this structure:
  • Topic sentence/contention - "This statement is reasonably accurate...."
  • Explanation (pluses and minuses) - "On the one hand..." and "On the other hand/However..."
  • (Diagrams and reference to these diagrams to illustrate your point(s))
  • Final judgement call - "Overall, it is accurate to say that catalysts lower the activation energy - but it is more accurate to say that they provide a different reaction mechanism/pathway which happens to have a lower activation energy."
Ensure you make a final judgement call on this question when answering it.

On a side note - I think this question could be better worded/modified. Depicting the lowering of the activation energy via the Maxwell Boltzmann distribution curve and explaining the relationship between reaction rate and lower activation energies using collision theory does not support the statement that "catalysts lower the action energy" but, rather, merely assume that statement is true and uses it to extrapolate other things (eg. that catalysts can increase reaction rates).
The question as written - could - be reasonable if previous question parts, for example, show data depicting that adding a catalyst without increasing reactant concentration or temperature is shown to increase a reaction rate, and you are expected to deduce that the only way a catalyst could increase the reaction rate is by lowering the activation energy. Was this the case?
could you have a look over my response
 

CM_Tutor

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On a side note - I think this question could be better worded/modified. Depicting the lowering of the activation energy via the Maxwell Boltzmann distribution curve and explaining the relationship between reaction rate and lower activation energies using collision theory does not support the statement that "catalysts lower the action energy" but, rather, merely assume that statement is true and uses it to extrapolate other things (eg. that catalysts can increase reaction rates).
The question as written - could - be reasonable if previous question parts, for example, show data depicting that adding a catalyst without increasing reactant concentration or temperature is shown to increase a reaction rate, and you are expected to deduce that the only way a catalyst could increase the reaction rate is by lowering the activation energy. Was this the case?
These comments reflect some of my own thoughts on reading the question. Maxwell-Boltzmann is a suitable tool for explaining why the alternative pathway of lower activation energy results in a higher rate. If we start from an observation that a catalyst does increase rate, Maxwell-Boltzmann provides an explanation for a plausible mechanism. However, I have to agree strongly with thush@decode that the assessment of accuracy of the given statement is incomplete with the given tools. If I were marking such a question, I would credit an answer that noted the deficiency in its structure, but how that might be viewed by other markers (on a trial, say) is unknowable.
 

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