Chemistry questions and solutions

Browse original practice and official past-paper questions. Each question has its own link, with its source and worked solution.

364 questions · Page 1 of 16

1. Q1 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 1 Which species is produced at the cathode during the electrolysis of an aqueous copper sulfate (CuSO4) solution using platinum electrodes? (A) Cu(s) (B) H2(g) (C) O2(g) (D) SO2(aq)
   Redox and electrochemistry
2. Q2 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 2 Determine the tertiary haloalkane. (A) 2,2-dibromobutane (B) 2,3,3-tribromobutane (C) 2-bromo-2-methylbutane (D) 2-bromo-3-methylbutane
   Organic chemistry
3. Q3 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 3 Identify the amphiprotic species. +(aq) (A) NH4 (B) H3O+(aq) 2−(aq) (C) CO3 −(aq) (D) HCO3
   Acids, bases and titration
4. Q4 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 4 Which type of reaction occurs when an alcohol reacts with a carboxylic acid to form an ester? (A) addition (B) hydrolysis (C) condensation (D) polymerisation
   Organic chemistry
5. Q5 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 5 A 25.00 mL aliquot of aqueous potassium hydroxide (KOH) solution was titrated against an aqueous solution of 0.100 M hydrochloric acid (HCl). It took 17.45 mL of HCl to reach the equivalence point. Determine the concentration of the KOH(aq) solution. (A) 2.29 × 10−1 M (B) 1.43 × 10−1 M (C) 6.98 × 10−2 M (D) 4.36 × 10−5 M
   Acids, bases and titration
6. Q6 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 6 Determine which statement is true for an electrolytic cell used for electroplating. (A) The redox reaction is spontaneous. (B) The anode is the object to be plated. (C) The cathode is reduced to replenish the metal ions. (D) The electrolyte contains the metal ions that plate the object.
   Redox and electrochemistry
7. Q7 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 7 Which of the following is exchanged with the surroundings when a chemical reaction reaches dynamic equilibrium? (A) gases (B) matter (C) energy (D) products
   Chemical equilibrium
8. Q8 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 8 Which is the most concentrated weak base? (A) 2.0 M KOH(aq) (B) 0.2 M NaOH(aq) (C) 2.0 M NH4OH(aq) (D) 0.2 M Al(OH)3(aq)
   Acids, bases and titration
9. Q9 · 2025 QCAA · Paper 1 · 1 mark
   QUESTION 9 Which protein structure contains two or more protein chains bonded together to form subunits? (A) primary (B) secondary (C) tertiary (D) quaternary
   Polymers and biomolecules
10. Q10 · 2025 QCAA · Paper 1 · 1 mark
    QUESTION 10 Methane (CH4) reacts with water to produce carbon monoxide (CO) and hydrogen (H2). CH4(g) + H2O(g) → CO(g) + 3H2(g) Determine the reducing agent. (A) H in H2 (B) C in CH4 (C) H in CH4 (D) O in H2O
    Redox and electrochemistry
11. Q11 · 2025 QCAA · Paper 1 · 1 mark
    QUESTION 11 Yeasts are used in the production of ethanol by fermentation to (A) increase the rate of the reaction. (B) act as a reactant in the overall reaction. (C) increase the yield of ethanol and ensure its purity. (D) produce green ethanol by preventing the production of carbon dioxide.
    Chemical synthesis
12. Q12 · 2025 QCAA · Paper 1 · 1 mark
    QUESTION 12 Predict the colour change that occurs when 1-propanol is oxidised to propanoic acid using acidified potassium dichromate (VI). (A) red to yellow (B) orange to green (C) purple to brown (D) pink to colourless
    Organic chemistry
13. Q13 · 2025 QCAA · Paper 1 · 1 mark
    QUESTION 13 Which monosaccharide undergoes a condensation reaction with glucose to form sucrose? (A) galactose (B) fructose (C) glucose (D) maltose
    Polymers and biomolecules
14. Q14 · 2025 QCAA · Paper 1 · 1 mark
    QUESTION 14 Increasing the pH of an aqueous solution of hydrochloric acid (HCl) from 2 to 4 (A) reduces the strength of the acid. (B) increases the acidity of the solution. (C) increases the concentration of H+ ions by a factor of 2. (D) reduces the concentration of H+ ions by a factor of 100.
    Acids, bases and titration
15. Q15 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 15–16 Questions 15–16 refer to the galvanic cell shown. Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s) V Salt bridge Zn Ag QUESTION 15 Calculate the cell potential for the galvanic cell under standard conditions. (A) +0.04 V (B) +0.84 V (C) +1.56 V (D) +2.36 V
    Redox and electrochemistry
16. Q16 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 15–16 Questions 15–16 refer to the galvanic cell shown. Zn(s) | Zn2+(aq) || Ag+(aq) | Ag(s) V Salt bridge Zn Ag QUESTION 16 Deduce the reaction occurring at the anode for the galvanic cell. (A) Zn2+(aq) + 2e−  Zn(s) (B) Zn(s)  Zn2+(aq) + 2e− (C) Ag(s)  Ag+(aq) + e− (D) Ag+(aq) + e−  Ag(s)
    Redox and electrochemistry
17. Q17 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 17–18 Questions 17–18 refer to the relationship between the concentration of nitrogen (N2), hydrogen (H2) and ammonia (NH3) in a closed system, as shown. N2(g) + 3H2(g)  2NH3(g) + heat NH3 Concentration (mol L−1) H2 N2 t1 Time (min)

    QUESTION 17 Determine the equilibrium law expression (Kc) for the reaction. [ ] 2 NH 3 (A) K = c [ ] [ ] N 3 H 2 2…
    Chemical equilibrium
18. Q18 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 17–18 Questions 17–18 refer to the relationship between the concentration of nitrogen (N2), hydrogen (H2) and ammonia (NH3) in a closed system, as shown. N2(g) + 3H2(g)  2NH3(g) + heat NH3 Concentration (mol L−1) H2 N2 t1 Time (min)

    QUESTION 18 Determine the change applied to the system at t1. (A) N2(g) was added. (B) Pressure was increased. (C…
    Chemical equilibrium
19. Q19 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 19–20 Questions 19–20 refer to the reversible chemical reaction and enthalpy level diagram shown. 2AB2(g) + B2(g)  2AB3(g) 100 80 Energy (kJ mol−1) 60 40 20 0 Progress of forward reaction QUESTION 19 Which statement is true for the forward reaction? (A) Energy is a product. (B) The reaction is endothermic. (C) Enthalpy change (ΔH) is positive.…
    Chemical equilibrium
20. Q20 · 2025 QCAA · Paper 1 · 1 mark
    QUESTIONS 19–20 Questions 19–20 refer to the reversible chemical reaction and enthalpy level diagram shown. 2AB2(g) + B2(g)  2AB3(g) 100 80 Energy (kJ mol−1) 60 40 20 0 Progress of forward reaction QUESTION 20 Determine the activation energy (Ea) of the reverse reaction. (A) 20 kJ mol−1 (B) 40 kJ mol−1 (C) 60 kJ mol−1 (D) 80 kJ mol−1
    Chemical equilibrium
21. Q21 · 2025 QCAA · Paper 1 · 2 marks
    QUESTION 21  (2 marks) An unknown acid, HA, undergoes 1.3% ionisation in an aqueous solution. HA(aq) + H2O(l)  H3O+(aq) + A−(aq) a) Classify HA as a strong or weak acid. [1 mark] b) Explain whether HA is a monoprotic or polyprotic acid. [1 mark]
    Acids, bases and titration
22. Q22 · 2025 QCAA · Paper 1 · 2 marks
    QUESTION 22  (2 marks) Determine the oxidation state of manganese in Mn2O3 and name the ionic compound. Oxidation state (Mn): Name of ionic compound (Mn2O3):
    Redox and electrochemistry
23. Q23 · 2025 QCAA · Paper 1 · 2 marks
    QUESTION 23  (2 marks) Identify two limitations associated with standard electrode (reduction) potentials (E°). 1: 2:
    Redox and electrochemistry
24. Q24 · 2025 QCAA · Paper 1 · 4 marks
    QUESTION 24  (4 marks) Citronellol is a common ingredient used in the fragrance industry and a component of citronella oil, an insect repellant. Its structure is shown. CH3 CH3 CH3 CH3 CH3 CH3 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 C CH CH CH CH OH OH a) Classify citronellol as saturated or unsaturated. Explain your reasoning. [2 marks] b) Describe a chemical tes…
    Organic chemistry