Learn Use unfamiliar values and changed assumptions to defend a chemical conclusion.
These 12 original public cases sample the current chemistry sequence. Six require calculations and six require an evidence-based choice. They do not cover every course objective. Explain your reasoning before recording a response; a matching number or choice does not automatically grade the explanation.
First and latest responses, up to three attempts and known feedback exposure are retained in science backups. Explanation drafts remain editable after feedback. Returning later or importing an older backup does not make an exposed case fresh. Keys are inspectable in this static application: this is practice, not a secure exam or independent mastery assessment.
0/12 cases attempted; 0/12 first responses match the keys. Unattempted cases supply no evidence. These counts do not change lesson completion or award course mastery.
A 0.80 mol/L stock must supply 300 mL of 0.12 mol/L final solution with no solute loss or reaction. What stock volume is needed, in mL?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
A mass is bounded by 23.8–24.2 g and displaced volume by 7.8–8.2 mL. What is the largest density consistent with these bounds? Round to two decimal places in g/mL.
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
For Ca²⁺ + CO₃²⁻ → CaCO₃, feeds contain 0.060 mol calcium ions and 0.040 mol carbonate ions. With rounded target molar mass 100 g/mol and complete target formation, what theoretical target mass is possible?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
A process has a 4.00 g theoretical target. Its 4.50 g isolate is independently assigned 80% target by mass. What is the corrected yield, as a percentage?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
An insulated teaching calorimeter contains 50 g solution with specific heat 4.0 J/(g K); the cup heat capacity is 20 J/K. Both warm by 3 K. How much heat did the solution and cup gain together?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
A hypothetical M²⁺ + 2e⁻ → M deposition receives 500 C total charge; 60% goes to this target reaction. Using F = 96500 C/mol, how many mmol of M form? Round to three decimal places.
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
In a reversible two-state model at fixed temperature, a catalyst multiplies both forward and reverse rate constants by the same factor greater than one. Which result follows?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
A scratched copper coating and exposed iron share an aerated electrolyte. Electrical contact between copper and iron is removed, but exposed iron remains wet. What does the qualitative model support?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
A balanced cell reaction has standard potential +0.50 V and transfers 2 mol electrons per mole of reaction. Its equation is doubled at unchanged conditions. How do standard potential and reaction free energy scale?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
Two substances share a molecular formula but have different normal boiling points. Which next step best supports a structure-property explanation?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
Of 200 kg original polymer, 120 kg is collected. Of that collected amount, 90 kg is usable and 30 kg is residue. Which final mass balance is valid?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
Two successive net masses after a drying sequence are 8.01 g and 8.00 g, each with an assigned ±0.01 g reading bound. Which conclusion is supported by those readings alone?
Explain the mechanism, evidence and assumptions. This saved draft stays editable after feedback; it is not a locked first-attempt explanation and is not automatically graded.
0/3 attempts recorded. No recorded feedback exposure in this notebook.
For each response, identify the system boundary, quantities and units, relevant mechanism, assumptions and a limitation. Explain what evidence would change your conclusion. If you revise after feedback, describe the error you repaired. A current explanation draft can reflect later learning and is not a locked record of prior understanding.
A reviewer should examine the explanations alongside the unknown-sample project and a fresh task with changed evidence. Check calculations, causal reasoning and alternatives separately. Public practice does not establish laboratory technique, independent investigation or AP readiness.
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