For students & instructors
Practice with a clear model.
This tool turns the lab-final review into repeatable practice: choose a topic, try the problem, compare your method with the worked steps, and try new values. It covers the review's calculation families and its final-slide concentration and Lewis-structure questions.
How to use your attempts
Complete each answer field and select Check my answer. A valid attempt unlocks the solution, including when your answer needs correction. Reveal one step at a time, revise your answer, or open the full worked solution. New problem generates fresh practice in the selected topic, or selects another topic when mixed review is active; Another like this stays with the current topic. Mixed review gives extra weight to unpracticed topics and topics whose latest recorded first attempt was incorrect.
Calculated quantities allow 1% relative rounding tolerance. Lewis electron and lone-pair counts require the exact integer count. Aim for three significant figures in calculated quantities and carry extra digits through intermediate steps; significant figures are not graded separately. Scientific notation such as 2.46e-3 works. A tiny nonzero answer is not accepted as zero. The units beside a field are the required units; enter the number alone.
Progress records the first valid attempt on each displayed problem. Rechecking that problem does not add another attempt. These counts are study feedback, not secure grades or a validated measure of mastery. Worked steps come from explicit equations and authored explanation templates. The tool does not interpret arbitrary written reasoning.
What you can practice
| Problem type | What the steps teach | Slides |
|---|---|---|
| Nonelectrolyte freezing point | Mass to moles, molality, ideal i = 1, positive ΔTf, and final aqueous freezing point. | 3–6, 11–14 |
| Electrolyte freezing point | Balanced ion dissociation, ideal particle count, and ΔTf = iKfm. | 7–10 |
| Ksp from solubility: 1:1 | Saturated AgCl, a dissolution ICE table, and Ksp = s². | 16–19 |
| Ksp from solubility: 1:2 | CaF₂ produces s of Ca²⁺ and 2s of F⁻; Ksp = 4s³. | 20–23 |
| Ksp from solubility: 2:1 | Ag₂CO₃ produces 2s of Ag⁺ and s of CO₃²⁻ in the stated simplified model; Ksp = 4s³. | 24–27 |
| Ksp with an initial common ion | AgCl dissolution adds s to the initial Ag⁺ concentration: Ksp = (c₀ + s)s. | 28–30 |
| Solubility with a common ion | Solve the positive quadratic root and test the stated s/c₀ < 0.05 approximation criterion. | 31–34 |
| KOH titrated with HCl | 1:1 neutralization, matching volume units, and original KOH molarity. | 36–39 |
| Acetic acid titrated with NaOH | 1:1 equivalence stoichiometry and the acid's original analytical molarity. | 40–42 |
| H₂SO₄ titrated with KOH | Complete neutralization: 2 mol KOH per 1 mol H₂SO₄. | 43–45 |
| Ba(OH)₂ titrated with HCl | 2 mol HCl per 1 mol Ba(OH)₂; formula-unit concentration differs from hydroxide concentration. | 46–48 |
| Molarity | Definition and calculations: moles of solute per liter of final solution. | 49 |
| Molality | Definition and calculations: moles of solute per kilogram of solvent. | 49 |
| Lewis structures & partial charges | Electron counts, lone pairs, local geometry, partial charges, and a model drawing for self-check. | 49 |
Read the model before calculating
Freezing: the tool uses water, Kf = 1.86 °C·kg/mol, and a pure-water freezing point of 0.00 °C. The depression ΔTf is a positive magnitude; subtract it from the pure-solvent temperature. Nonelectrolytes have ideal i = 1. Electrolyte exercises assume the stated ideal dissociation; real particle effects can deviate from that approximation. Read about colligative properties in OpenStax.
Solubility: every exercise assumes a saturated solution at equilibrium with excess solid at a fixed temperature. Generated solubilities and Ksp values are hypothetical teaching data, not literature measurements for the named salts. The model treats ions as ideal and neglects secondary equilibria. The thermodynamic constant is dimensionless: concentrations are normalized by c° = 1 mol/L. The familiar classroom shorthand uses the numerical concentrations in M. Read about saturation, ion products, and common ions.
In the Ag₂CO₃ model, carbonate protonation/hydrolysis and silver complex formation are neglected, so free [CO₃²⁻] is set equal to s. The same general neglect of side reactions also applies to the other solubility exercises. Those assumptions matter when relating the algebra to real aqueous chemistry. Read about coupled equilibria.
Titration: measured endpoints are treated as equivalence points, using balanced-reaction mole ratios. The requested molarity is the original sample concentration. Sulfuric-acid problems specify full neutralization of both protons. Acetic-acid equivalence stoichiometry does not imply that its equivalence-point pH is 7. The tool does not calculate titration curves or pH. Read about titration stoichiometry.
Molecular drawings: draw the molecule on paper and compare it with the solution. The tool grades structured checkpoints, not your sketch. Its finite bank contains H₂O, HCl, NH₃, HBr, CH₃OH, and CH₃CH₂MgBr; repeated molecules are expected. Partial charges describe bond polarity and differ from formal charges. For C–Mg, C is δ− and Mg is δ+. The Grignard picture is a simplified covalent bookkeeping representation, not a complete account of aggregation or solvation. Read about the electron-rich carbon of Grignard reagents.
For more background, review OpenStax's solubility rules and balanced chemical reactions.
Your work stays in your browser
No student account, API key, or external generation service is needed. This app sends no answers or scratchpad working to a server and includes no analytics. It saves only per-topic practice counts and the most recent recorded first-attempt outcome in this browser. It does not save your answer text, scratchpad, name, or student identifier. Reset clears those local practice records; if browser storage is unavailable, counts last only for the current session. The hosting provider may keep ordinary website request logs.
A copied problem link contains a topic, generator version, and random seed. With the same generator version and unchanged code, that link reproduces the same problem. It includes no student answers or working. New problems draw from bounded teaching data, so values or molecular variants can repeat.