IB Chemistry HL Internal Assessment Example

The research question is sharply defined and embedded within the specific context of luminol chemiluminescence and reaction kinetics, demonstrating excellent alignment with criterion expectations.

The background section explains collision theory broadly but does not link explicitly to the luminol mechanism. Add a sentence connecting collision frequency to chemiluminescence intensity.

The second equation includes an extra “Time” term after the fraction. Correct the formula so it reads $$\text{Average rate}=\frac{\text{Quantity of products}}{\text{Time}}$$

The table of other rate factors is well organised and clearly explains causes, showing solid methodological consideration.

In the balanced redox equation, the sodium ion is written as Na*. It should appear as Na^+ to reflect its true charge.

The mechanism narrative is dense and does not note the pH requirements for dianion formation. Consider adding why NaOH concentration matters.

The hypothesis unit “1x s⁻¹” is unclear. It should specify “lx s⁻¹” for light production rate.

The hypothesis is logically derived from the background and clearly predicts how concentration affects rate.

The oxygen concentration table clearly presents reagent volumes and computed molarities, aiding reproducibility.

The table of variant combinations is concise and matches the described independent variables.

Consider controlling reaction temperature more precisely, for example by using a water bath, rather than a room with fluctuating conditions.

All controlled variables are thoroughly listed with justification, demonstrating strong planning for fair comparisons.

The materials list cites 0.1 M NaOH but the method uses 3% NaOH. Resolve this inconsistency to ensure reproducibility.

The experimental setup diagram is clear and shows all key components, aiding replication.

The stepwise procedure is fully numbered and labeled, allowing reproducibility with minimal ambiguity.

Steps 1–4 lack detail on mixing speed and darkness conditions. Specify logging frequency and ambient light control.

The calculation of luminol concentrations in the table omits units and has rounding inconsistencies. Label all values to three significant figures.

The sample calculation shows C = 0.1364 mol dm⁻³ instead of the correct 0.01364 mol dm⁻³. Check the volume conversion factor.

The dependent-variable table lists a stopwatch with ±0.001 s precision, which exceeds typical smartphone stopwatch accuracy. Use ±0.01 s.

Outliers in R₃ and R₄ are removed without justification. Apply a statistical test (e.g., Grubbs’) to support exclusion.

Absolute uncertainties are calculated and tabulated correctly, demonstrating clear handling of random errors.

The secondary chart of average‐rate sample calculation is well illustrated, enhancing clarity of uncertainty propagation.

The raw data table contains misaligned symbols and stray vertical bars. Reformat or retype for clear communication.

Processed data table clearly labels ΔTime and ΔLight with uncertainties, aiding precise rate calculations.

The scatter plot displays clear trends but lacks regression equations and R² values. Add them to strengthen quantitative analysis.

The processed‐data concentration vs average‐rate table rounds A3’s luminol concentration inconsistently (0.008886 vs 0.00580 earlier). Use consistent rounding.

The percentage‐change table summarises relative impacts but does not link back to literature kinetic orders. Discuss expected first-order behavior.

Variant “B2” is referenced instead of “A2” in the conclusion text, leading to confusion. Correct the label for consistency.

The conclusion effectively addresses the research question and is broadly consistent with the trends in processed data.

The error and improvement table identifies specific impurities and temperature fluctuations, illustrating thoughtful evaluation.

Some suggested improvements remain qualitative (e.g., “higher‐quality reagents”) without quantifying the expected effect on uncertainty. Include estimates.