CSCA Chemistry Practice Questions: 8 Worked Answers
Practice eight original CSCA Chemistry-style questions with worked answers on moles, solutions, pH, redox, equilibrium and laboratory chemistry.
CSCA Chemistry practice questions are most useful when you can explain each choice, not only calculate the final number. The published syllabus covers chemical calculations, properties and reactions, chemical theory, and experiments. These eight original multiple-choice examples show a repeatable solution method. They are not official CSCA questions or past papers; use them to diagnose gaps before a timed practice set.
What does the CSCA Chemistry paper cover?
- Format: 48 single-answer multiple-choice questions in 60 minutes, scored from 0 to 100.
- Language: Chemistry is available in Chinese or English, subject to your target university’s requirements.
- Syllabus modules: basic chemical concepts and calculations; properties and reactions of substances; chemical theories and laws; chemical experiments and applications.
- The following are original learning examples, not a sample of the official paper’s exact difficulty or topic weighting.
Start with the official CSCA syllabus and our Chemistry syllabus guide. A short worked set cannot replace the full topic checklist. When you review a wrong answer, decide whether the cause was a definition, a chemical equation, a unit conversion or a mistaken assumption. That diagnosis determines what to practice next.
How do mole and solution-concentration questions work?
Original practice question — molar concentration. A solution contains 0.50 mol of dissolved solute in a final solution volume of 250 mL. What is its concentration?
- A. 0.125 mol/L
- B. 0.50 mol/L
- C. 2.0 mol/L
- D. 125 mol/L
Worked answer: C — 2.0 mol/L
Choose the relationship
Molar concentration c = n/V, with solution volume V in liters. Convert 250 mL to 0.250 L before dividing.
Calculate and check
c = 0.50 mol ÷ 0.250 L = 2.0 mol/L. The answer describes the final solution, not the solvent volume before mixing.
Avoid the common trap
Using 250 without converting milliliters to liters gives a result smaller by a factor of 1,000. Write the units into the calculation.
Original practice question — dilution. How much 2.0 mol/L stock solution is needed to prepare 100 mL of a 0.50 mol/L solution by dilution?
- A. 20 mL
- B. 25 mL
- C. 50 mL
- D. 400 mL
Worked answer: B — 25 mL
Choose the relationship
Dilution keeps the amount of solute constant: c₁V₁ = c₂V₂. Here the stock is c₁ and the target solution is c₂.
Calculate and check
V₁ = (0.50 mol/L × 100 mL) ÷ 2.0 mol/L = 25 mL. Add solvent until the final solution volume is 100 mL.
Avoid the common trap
Do not add 100 mL of solvent to 25 mL of stock; that would make more than 100 mL of final solution.
Concentration problems often hide a unit or wording trap. “Final volume” means the volume after the solution is made, and dilution changes volume while conserving solute amount. For more calculations, use free Chemistry practice and revisit this guide only for the steps you miss. The CSCA exam overview explains the broader test context.
How do pH and gas-calculation questions work?
Original practice question — strong-acid pH. Assume a fully dissociated monoprotic strong acid has concentration 0.001 mol/L at 25 °C. What is the approximate pH?
- A. 1
- B. 3
- C. 7
- D. 11
Worked answer: B — pH 3
Choose the relationship
A fully dissociated monoprotic acid gives [H⁺] approximately equal to the stated acid concentration: 10⁻³ mol/L.
Calculate and check
pH = −log₁₀[H⁺] = −log₁₀(10⁻³) = 3. This approximation fits the conditions stated in the question.
Avoid the common trap
Do not use this shortcut automatically for weak acids or solutions with other important sources of hydrogen ions. Check the assumptions first.
Original practice question — ideal gas volume. An ideal gas sample contains 0.10 mol at 300 K and 100 kPa. Using R = 8.31 kPa·L/(mol·K), what is its approximate volume?
- A. 0.249 L
- B. 2.49 L
- C. 24.9 L
- D. 249 L
Worked answer: B — 2.49 L
Choose the relationship
Use PV = nRT. The provided gas constant uses kPa and liters, so the stated pressure can be used directly.
Calculate and check
V = nRT/P = (0.10 × 8.31 × 300)/100 L = 2.493 L, approximately 2.49 L.
Avoid the common trap
A different value of R may require pascals and cubic meters. Never mix unit systems without conversion, and use kelvin for temperature.
How do stoichiometry and redox questions work?
Original practice question — limiting reactant. For 2H₂ + O₂ → 2H₂O, 4.0 mol of H₂ reacts with 1.0 mol of O₂. What is the maximum amount of H₂O formed?
- A. 1.0 mol
- B. 2.0 mol
- C. 4.0 mol
- D. 8.0 mol
Worked answer: B — 2.0 mol
Choose the relationship
The balanced equation uses 2 mol H₂ for each 1 mol O₂ and produces 2 mol H₂O. Compare the available amounts with that ratio.
Calculate and check
1.0 mol O₂ consumes only 2.0 mol H₂, so O₂ is limiting and produces 2.0 mol H₂O. Some H₂ remains unused.
Avoid the common trap
Do not assume that all 4.0 mol of H₂ react just because they are present. Identify the limiting reactant before applying product ratios.
Original practice question — oxidation and reduction. In Zn + Cu²⁺ → Zn²⁺ + Cu, which statement is correct?
- A. Zn gains two electrons
- B. Cu²⁺ loses two electrons
- C. Zn is oxidized
- D. No electrons are transferred
Worked answer: C — Zn is oxidized
Choose the relationship
Track oxidation states or write half-reactions. Zinc changes from 0 to +2, while copper changes from +2 to 0.
Calculate and check
Zn → Zn²⁺ + 2e⁻ is electron loss, so zinc is oxidized. Cu²⁺ + 2e⁻ → Cu is electron gain, so copper ions are reduced.
Avoid the common trap
The names oxidation and reduction refer to electron loss and gain respectively. A rising oxidation state signals oxidation.
Balanced coefficients describe mole ratios, but they do not tell you which reagent limits a particular mixture. In redox, write electrons on the correct side of each half-reaction. These two checks prevent many errors even when the substances are unfamiliar. The published syllabus also includes ionic reactions, organic basics and common inorganic substances, so continue beyond these examples.
How do equilibrium and laboratory questions work?
Original practice question — pressure and equilibrium. For gaseous N₂ + 3H₂ ⇌ 2NH₃ at fixed temperature, which side is favored at equilibrium if pressure is increased by reducing volume?
- A. Reactants, with four gas moles
- B. Products, with two gas moles
- C. Neither side
- D. The reaction stops
Worked answer: B — products
Choose the relationship
Count gaseous moles on each side of the balanced equation: four on the left and two on the right.
Calculate and check
Increasing pressure by reducing volume favors the side with fewer gas molecules, so the equilibrium composition shifts toward NH₃ under these stated conditions.
Avoid the common trap
A shift in equilibrium position does not mean the reaction has stopped or that every practical process instantly reaches the new equilibrium. Temperature changes need separate analysis.
Original practice question — chloride-ion test. A solution gives a white precipitate when aqueous silver nitrate is added. Which ion is supported by this observation in this simplified test?
- A. Cl⁻
- B. NO₃⁻
- C. Na⁺
- D. H⁺
Worked answer: A — chloride ion
Choose the relationship
The relevant ionic reaction is Ag⁺(aq) + Cl⁻(aq) → AgCl(s). Silver chloride is a white precipitate.
Calculate and check
The observation supports chloride under the simplified conditions of this question. In real analysis, follow the full laboratory procedure and confirmatory steps before identifying an unknown sample.
Avoid the common trap
Do not infer that any white precipitate always proves chloride. Other precipitates and interfering ions are possible; context and confirmation matter.
How should you prepare for a timed Chemistry paper?
A practical review loop
Map your topics
Check the current syllabus and mark calculations, reactions, theory and experiments as strong, uncertain or new.
Solve before reading
Try every question above without the answer steps, then write one sentence naming the governing principle.
Redo wrong answers
Keep a small log of unit conversions, balancing errors, assumptions and definitions. Retry after a day or two.
Mix and time
Move from topic drills to mixed questions and a full-length 60-minute practice session.
The published format averages 75 seconds per question across 48 items in 60 minutes. Some calculations take longer and some concept questions take seconds, so train for overall pacing rather than forcing a rigid limit on every item. Use a mock-test practice routine, then check official instructions for what tools and working materials are allowed in your specific session.
Frequently asked questions
CSCA FAQ
Are these official CSCA Chemistry past-paper questions?
No. They are original educational questions aligned with published syllabus topics, not official samples, recalled questions or past papers.
How many Chemistry questions are on the CSCA?
The published format lists 48 single-answer multiple-choice questions in 60 minutes, with a score from 0 to 100.
Can I take CSCA Chemistry in English?
The published format offers Chemistry in Chinese or English. Follow your intended university’s language requirement.
Does this page cover the entire syllabus?
No. It samples calculations, reactions, theory and experiments. Review the full official syllabus and practice additional subtopics before your exam.
CSCA.ai is an independent preparation platform. Confirm dates, fees and requirements on the official site, csca.cn.
