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.SL

Official IB Result

16/24

General feedback

16/24

No overall summary is available for this report.

5.1·Weakness

Page 3• Click to view

The disproportionation reaction equation has formatting errors (e.g., superscripts and species labels). Ensure correct chemical notation for clarity: e.g.

e x t S_{2} e x t O_{3}^{2 -} + 2 e x t H^{+} i g h t a r r o w e x t S + e x t H_{2} e x t O + e x t S O_{2} .

5.2·Suggestion

Page 6• Click to view

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

Page 7• Click to view

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

Page 17• Click to view

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

Page 23• Click to view

Including a strengths table demonstrates reflection on experimental design, which is commendable. These strengths align with methodological considerations and improve reliability.

5.6·Suggestion

Page 26• Click to view

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

Criteria Strands

A.1Research question context

Excellent

A.2Methodological considerations

Good

A.3Methodology description

Good

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

Page 1• Click to view

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

Page 2• Click to view

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

Page 2• Click to view

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

Page 3• Click to view

The chemical background explaining thiosulfate structure and redox roles is detailed and shows strong understanding, reinforcing methodological choices.

1.5·Strength

Page 4• Click to view

The description of collision theory and Maxwell–Boltzmann distribution concisely links theory to temperature effects, supporting the experimental rationale.

1.6·Suggestion

Page 8• Click to view

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

Page 8• Click to view

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

Criteria Strands

B.1Communication of data recording and processing

Good

B.2Consideration of uncertainties

Moderate

B.3Data processing quality

Good

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

Page 11• Click to view

Raw data tables include clear headings, units, and significant figures, effectively communicating the data set and experimental design.

2.2·Strength

Page 16• Click to view

Expressing reaction rate as the inverse of mean time (

rate = \frac{1}{t ˉ}

) is a clear and appropriate approximation given the measurement method.

2.3·Weakness

Page 16• Click to view

The formula

ar{x} = \frac{\Sigma x_i}{x}

is incorrect; the denominator should be the number of trials,

n

. Correct to

\overset{x}{ˉ} = \frac{\sum x _{i}}{n}

to avoid misinterpretation.

2.4·Weakness

Page 17• Click to view

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

Page 18• Click to view

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

Page 19• Click to view

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

Page 19• Click to view

Include a worked example of standard deviation calculation showing all deviation terms and final value to clarify how variability was quantified.

2.8·Suggestion

Page 20• Click to view

The formula for Pearson’s

r

is stated correctly, but intermediate sums and deviations are omitted. Show key values (e.g.

s u m (x - ba r x) (y - ba r y)

) for transparency.

Criteria C: Conclusion

3/6

Criteria Strands

C.1Conclusion relevance and support

Good

C.2Scientific context comparison

Moderate

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

Page 21• Click to view

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

Criteria Strands

D.1Methodological weaknesses

Good

D.2Suggested improvements

Moderate

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

Page 24• Click to view

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

Page 24• Click to view

The limitations table lists specific systematic and random errors, providing clear insight into weaknesses. This reflects thoughtful evaluation of methodological impact.

4.3·Suggestion

Page 25• Click to view

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.

Loading scores...

Official IB Result

16/24

General feedback

16/24

No overall summary is available for this report.

5.1·Weakness

Page 3• Click to view

The disproportionation reaction equation has formatting errors (e.g., superscripts and species labels). Ensure correct chemical notation for clarity: e.g.

e x t S_{2} e x t O_{3}^{2 -} + 2 e x t H^{+} i g h t a r r o w e x t S + e x t H_{2} e x t O + e x t S O_{2} .

5.2·Suggestion

Page 6• Click to view

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

Page 7• Click to view

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

Page 17• Click to view

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

Page 23• Click to view

Including a strengths table demonstrates reflection on experimental design, which is commendable. These strengths align with methodological considerations and improve reliability.

5.6·Suggestion

Page 26• Click to view

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

Criteria Strands

A.1Research question context

Excellent

A.2Methodological considerations

Good

A.3Methodology description

Good

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

Page 1• Click to view

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

Page 2• Click to view

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

Page 2• Click to view

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

Page 3• Click to view

The chemical background explaining thiosulfate structure and redox roles is detailed and shows strong understanding, reinforcing methodological choices.

1.5·Strength

Page 4• Click to view

The description of collision theory and Maxwell–Boltzmann distribution concisely links theory to temperature effects, supporting the experimental rationale.

1.6·Suggestion

Page 8• Click to view

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

Page 8• Click to view

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

Criteria Strands

B.1Communication of data recording and processing

Good

B.2Consideration of uncertainties

Moderate

B.3Data processing quality

Good

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

Page 11• Click to view

Raw data tables include clear headings, units, and significant figures, effectively communicating the data set and experimental design.

2.2·Strength

Page 16• Click to view

Expressing reaction rate as the inverse of mean time (

rate = \frac{1}{t ˉ}

) is a clear and appropriate approximation given the measurement method.

2.3·Weakness

Page 16• Click to view

The formula

ar{x} = \frac{\Sigma x_i}{x}

is incorrect; the denominator should be the number of trials,

n

. Correct to

\overset{x}{ˉ} = \frac{\sum x _{i}}{n}

to avoid misinterpretation.

2.4·Weakness

Page 17• Click to view

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

Page 18• Click to view

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

Page 19• Click to view

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

Page 19• Click to view

Include a worked example of standard deviation calculation showing all deviation terms and final value to clarify how variability was quantified.

2.8·Suggestion

Page 20• Click to view

The formula for Pearson’s

r

is stated correctly, but intermediate sums and deviations are omitted. Show key values (e.g.

s u m (x - ba r x) (y - ba r y)

) for transparency.

Criteria C: Conclusion

3/6

Criteria Strands

C.1Conclusion relevance and support

Good

C.2Scientific context comparison

Moderate

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

Page 21• Click to view

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

Criteria Strands

D.1Methodological weaknesses

Good

D.2Suggested improvements

Moderate

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

Page 24• Click to view

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

Page 24• Click to view

The limitations table lists specific systematic and random errors, providing clear insight into weaknesses. This reflects thoughtful evaluation of methodological impact.

4.3·Suggestion

Page 25• Click to view

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.