IB Chemistry HL Internal Assessment Example

The listing “(1, 2, 3, 4, 4) and 5 hours” appears to include a duplication error; clarify the intended time intervals to ensure accuracy.

Background effectively outlines chemical structure and oxidation mechanism, but could more directly connect to the choice of iodometric titration conditions.

The research question is precisely contextualised with specific storage times and titration method, demonstrating a well-defined scope and relevance.

Mechanistic discussion enriches the theory but does not fully justify the concentration and volume of starch indicator used in titrations.

KI mass of 0.66 g per litre produces a 0.004 M solution, not 0.005 M; review molar mass calculations to correct concentration discrepancy.

Preliminary trials to select lemon over orange based on vitamin C difference and uncertainty are well reasoned and enhance the experimental design.

The adjustment of iodine concentration from 0.002 to 0.005 mol·dm⁻³ is mentioned but lacks calculation showing how this optimises titration volume for a 50 mL burette capacity.

Light intensity is described qualitatively but without measurement; consider quantifying light exposure (e.g., lux meter) to strengthen control.

Controlled variables are clearly described, especially storage conditions and juice consistency, which enhances the reliability of the experiment.

Excluding the practice titration from analysis demonstrates awareness of systematic error and improves data reliability.

Raw data table is comprehensive with uncertainties; however, splitting tables for each time point might improve clarity and reduce reading complexity.

Processed data section notes significant figures but omits a summary table of calculated concentrations; include processed data tables for transparency.

Calculation of moles by dividing volume by molar mass is incorrect; iodine moles should be molarity × volume in litres, not volume ÷ molar mass.

The concentration table is well structured, but ensure that significant figures in concentration reflect propagated uncertainties consistently.

Percent uncertainty uses 1.66 g mass instead of 0.66 g; correct the absolute uncertainty in KI mass to accurately propagate error.

Interpretation that uncertainties “do not overlap” contradicts the data; many intervals actually overlap, undermining this claim.

Calculated rate for hour 5 (0.0119×10⁵) is inconsistent with neighbouring values; re-evaluate rate calculations for uniform Δ[conc] and Δt.

$$r=-\frac{\Delta concentration}{\Delta reactionrate}$$ is miswritten; denominator should read $\Delta time$, so $$r=-\frac{\Delta [A]}{\Delta t}$$.

Applying Pearson’s critical value shows statistical rigor; linking R² to p-values demonstrates clear understanding of significance.

Claim that differential law exponential fit is significant at p=0.1 lacks clear justification; consider adding p-value calculation or confidence interval.

Conclusion clearly restates hypothesis and links to data trend, demonstrating coherence between research question and results.

The conclusion overstates certainty by not distinguishing between differential and integrated analysis outcomes; clarify varying levels of statistical support.

Discussion of literature context enriches scientific framing, but linking mechanisms back to own data could further strengthen the conclusion.

The evaluation explains specific impacts of storage condition variability, but quantitative assessment of temperature fluctuation effects could be added.

Improvements section would benefit from commentary on relative impact or feasibility (e.g., cost, time) to prioritize changes.

Limitations are specific and tied to impacts, and proposed improvements are realistic, showing depth in methodological evaluation.