IB Chemistry HL Internal Assessment Example

The title and research question context frames the study clearly within the nutritional and stability context of vitamin C, linking temperature effects to redox titration relevance.

The chemical caption contains typographical errors (C_e H_s O_g), undermining clarity; ensure precise chemical notation consistent with formula discussed.

Background section integrates literature effectively, establishing clear context for vitamin C importance in food, cosmetic, and pharmaceutical industries.

The balanced redox equation is correctly presented, reinforcing the chemical basis of the titration method.

Consider specifying the practical relevance of the selected temperature range (e.g., pasteurization or storage conditions) to strengthen the aim’s context.

The list item displays '-1.3 g of iodine' instead of '1.3 g', indicating a typographical error; correct values to avoid confusion in reagent preparation.

Controlled variables are well listed, but the student hasn’t addressed key confounders like pH and dissolved oxygen, which could influence vitamin C degradation.

Procedure includes an erroneous '100 L conical flask' and lacks heating time details, introducing ambiguity that could affect reproducibility.

Safety table entries are truncated and misaligned, lacking complete 'Precautions' details; ensure full safety instructions are presented.

Procedure for repeats is inconsistent: initial variables mention five trials per temperature, but step 10 lists only three repeats, risking data inconsistency.

Enhance qualitative section by including systematic observations or photographs for each temperature to support visual end-point consistency.

The 80°C trial 5 value (15.00 mL) is a clear outlier but isn’t addressed; how was this anomaly considered in data processing?

Table heading mislabels concentration as 0.005 mol/L⁻¹ and includes extraneous √ symbols, reducing precision in communication of data.

The stoichiometric calculation uses volume divided by molar mass rather than applying $n=cV$, leading to major inaccuracies in moles of iodine.

The concentration calculation appears inconsistent with prior moles and volume values; ensure units and decimal accuracy when computing $c=\frac{n}{V}$.

Calculation and clear reporting of Pearson’s $r=-0.91$ effectively quantify the strong negative relationship between temperature and vitamin C concentration.

When propagating instrument uncertainties, combine both volumetric pipette and titrant uncertainties rather than isolating one to reflect total measurement error.

The choice to propagate only the highest percentage uncertainty from burette readings omits variation across trials and underestimates the combined uncertainty.

Assigning a constant percentage uncertainty for all concentrations overlooks that temperature and volume variation could change relative uncertainties.

Reporting the regression equation and $R^2=0.83$ quantifies the rate of change and explanatory power, enhancing the quantitative analysis.

The conclusion highlights 25 °C as optimal without quantifying significance; consider statistical tests or confidence intervals to support this claim.

Identifies endpoint detection as a major limitation affecting accuracy, demonstrating awareness of methodological weaknesses.

Identifies juice degradation during storage but lacks quantification of how storage time influenced data, weakening evaluation depth.