AP Chemistry unknown-sample evidence capstone
A budgeted concentration, reaction and energy investigation
You have eight virtual mL of a fictional unknown acid. Recommend which candidate is consistent with concentration calibration, neutralization stoichiometry and calorimetry, or explicitly conclude that your purchased evidence is insufficient. Before opening each packet, record a prediction and why this test discriminates alternatives. Three core packets cost six virtual mL; the remaining two can fund one of two different control checks. Spending both controls first can leave insufficient budget for all core evidence: retain and explain that design failure rather than fabricating missing observations.
All candidates are stipulated pure, stable, soluble fictional substances with the same optical calibration in the supplied matrix. Their endpoint reaction consumes the listed moles of base per mole of acid formula units; enthalpy is per mole of acid formula units under the packet conditions. The candidate list is exhaustive only inside this teaching model. A real unknown could be a mixture, contaminated or absent from this list.
| Candidate | Base equivalents per acid formula unit | Neutralization ΔH (kJ/mol acid) |
|---|---|---|
| A | 1 | -57 |
| B | 1 | -40 |
| C | 2 | -75 |
This is original public numerical practice, not an unseen exam or a chemical handling procedure. Do not prepare, taste, mix, heat or dispose of actual unknown materials from this page. The virtual mL budget is a pedagogical allocation, not a practical safety specification.
Predict before revealing a packet
0/8 virtual mL used. Recorded packets cannot be refunded by an import.
Build the quantitative argument
- Fit A = mc + b, subtract the blank, and undo dilution. Carry the supplied absorbance bound to concentration.
- Use blank-corrected base volume and concentration. Compare base/acid amount with both equivalent-ratio hypotheses, including the concentration bound.
- Add receiver and cup heat capacities. Reverse the receiver heat sign for the reaction. Bound a temperature difference by adding the two absolute reading bounds, then use concentration bounds in the denominator.
- Compare candidate enthalpies with the resulting interval, not only a rounded central estimate. Explain which assumptions and rejected tests most affect your claim.
If a packet was not purchased, identify that missing evidence and limit the claim. A reviewer, not field completion, judges whether all three domains are adequately supported.
Draft edits save locally. First report, critique, revision and a separately assigned transfer case remain distinct. No automatic mastery, AP score or supervised laboratory credit is awarded.
Sources and transfer
All values and candidate properties are original stipulated teaching data. Relationships checked 30 October 2026 against OpenStax molarity, quantitative chemical analysis and calorimetry. Spectrophotometric calibration is supported by the calibration lesson. An educator can assign a different candidate table, nonlinear calibration or nonzero blank heat and review the response; repeating this public case is not unfamiliar transfer.
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