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Chemistry IA Exemplar: Sodium Thiosulfate Decomposition Temperature… | RevisionDojo
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IB Chemistry SL Internal Assessment Example
Investigating the varying temperatures (298.05K, 300.95K, 303.15K, 305.5K, 310.15K, 313.15K) on the rate of reaction of decomposition of sodium thiosulfate with hydrochloric acid by measuring the time (in seconds) taken for formation of a yellow precipitate.
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5
Official IB Result
16/24
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16/24
0
12
24
5.1·Weakness
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The disproportionation reaction equation has formatting errors (e.g., superscripts and species labels). Ensure correct chemical notation for clarity: e.g. extS2extO32−+2extH+ightarrowextS+extH2extO+extSO2.
5.2·Suggestion
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The heading “How will it be concentrated?” should read “How will it be controlled?” to match the content. Correct this terminology to avoid confusion.
5.3·Weakness
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The 50 mL graduated cylinder uncertainty is listed as "+1 mL" instead of “± 1 mL.” Update to the correct format for consistency in uncertainty reporting.
5.4·Suggestion
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The bar graph caption is split across two captions, making it hard to interpret. Combine the text into one coherent caption and label axes clearly.
5.5·Strength
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Including a strengths table demonstrates reflection on experimental design, which is commendable. These strengths align with methodological considerations and improve reliability.
5.6·Suggestion
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Reference formatting is inconsistent (missing access dates and uniform citation style). Use a consistent style (e.g. APA) and include all necessary elements for each source.
Criteria A: Research Design
5/6
0
3
6
Criteria Strands
Excellent
Research question context
Good
Methodological considerations
Good
Methodology description
Criteria Feedback
Research question framed within a specific medical context (enzyme therapy, cyanide poisoning)
Clear quantitative variables and physiological temperature range
Detailed methodological considerations (control of variables, thermostatic bath, number of trials)
Reproducible method description with concentrations, volumes and uncertainties
Minor ambiguities on timing protocol (simultaneous start of tubes, use of timers)
Incomplete discussion of simultaneous acid addition and temperature drop during transfer
1.1·Strength
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The aim clearly states the quantitative variables and context (temperature range relevant to physiological conditions), establishing a specific and appropriate scope for the research question.
1.2·Strength
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The introduction links the chemical kinetics investigation to enzyme therapy and cyanide poisoning treatment, providing a specific and medically relevant context rather than a generic background.
1.3·Strength
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The research question is clear, quantitative, and defines both independent and dependent variables with precise measurement, fulfilling the requirement for specificity and reproducibility.
1.4·Strength
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The chemical background explaining thiosulfate structure and redox roles is detailed and shows strong understanding, reinforcing methodological choices.
1.5·Strength
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The description of collision theory and Maxwell–Boltzmann distribution concisely links theory to temperature effects, supporting the experimental rationale.
1.6·Suggestion
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The method description is thorough, but it’s unclear if all five test tubes are started simultaneously or sequentially. Clarify this step to ensure reproducibility.
1.7·Suggestion
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Specify whether separate timers are used for each test tube or a single timer is restarted. This detail is critical for someone seeking to reproduce the timing protocol accurately.
Criteria B: Data Analysis
4/6
0
3
6
Criteria Strands
Good
Communication of data recording and processing
Moderate
Consideration of uncertainties
Good
Data processing quality
Criteria Feedback
Well-structured raw data tables with headings, units, significant figures
Clear graphs with error bars
Correct calculation of means, inverse-time rates and Pearson’s r
Evidence of consideration of uncertainties
Units omitted in one table and minor table formatting issues
Incorrect summation of percentage uncertainties and no propagation into final rates
No Arrhenius or gradient analysis; some rounding inconsistencies
2.1·Strength
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Raw data tables include clear headings, units, and significant figures, effectively communicating the data set and experimental design.
2.2·Strength
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Expressing reaction rate as the inverse of mean time (rate=tˉ1) is a clear and appropriate approximation given the measurement method.
2.3·Weakness
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The formula ar{x} = \frac{\Sigma x_i}{x} is incorrect; the denominator should be the number of trials, n. Correct to xˉ=n∑xi to avoid misinterpretation.
2.4·Weakness
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Table 9 omits the data row for 313.15 K even though it was in the research question. Including all temperatures ensures completeness in data processing.
2.5·Weakness
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Summing percentage uncertainties directly without propagation rules overestimates total uncertainty. Use quadrature for independent uncertainties or propagate appropriately into final rate values.
2.6·Weakness
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The combined uncertainty table mixes %uncertainty for time with rate calculations. Propagate timing uncertainty into s−1 rates for consistency with kinetic analysis.
2.7·Suggestion
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Include a worked example of standard deviation calculation showing all deviation terms and final value to clarify how variability was quantified.
2.8·Suggestion
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The formula for Pearson’s r is stated correctly, but intermediate sums and deviations are omitted. Show key values (e.g. sum(x−barx)(y−bary)) for transparency.
Criteria C: Conclusion
3/6
0
3
6
Criteria Strands
Good
Conclusion relevance and support
Moderate
Scientific context comparison
Criteria Feedback
Conclusion restates quantitative trend and references collision theory
Correlation coefficient is used to support the trend
Relevant comparison made to literature investigation
No integration of uncertainty into confidence of the conclusion
Lacks quantitative discussion of rate differences compared to literature
Scientific context comparison remains brief
3.1·Suggestion
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The conclusion restates findings and correlates with collision theory but does not discuss how the uncertainty affects confidence in the trend. Integrate uncertainty into your justification.
Criteria D: Evaluation
4/6
0
3
6
Criteria Strands
Good
Methodological weaknesses
Moderate
Suggested improvements
Criteria Feedback
Identifies four specific methodological weaknesses with their reliability impacts
Offers realistic improvements for each identified limitation
Includes extension idea comparing alternative compounds
Does not quantify how proposed improvements improve precision or accuracy
Relative magnitude of each weakness’s impact is not deeply analysed
4.1·Suggestion
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The improvement to add a second person for timing is realistic, but benefit to precision could be quantified. Explain how delay reduction translates to lower standard deviation.
4.2·Strength
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The limitations table lists specific systematic and random errors, providing clear insight into weaknesses. This reflects thoughtful evaluation of methodological impact.
4.3·Suggestion
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The extension idea to compare sodium thiosulfate to alternative compounds is relevant and realistic. To enhance this, propose specific metrics or reaction conditions to compare.
