QCEVault

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 4 of 16

  1. Q6 · 2024 QCAA · Paper 2 · 9 marks
    QUESTION 6  (9 marks) Six molecules were selected to investigate functional groups and the arrangement of atoms. O H H H H H H H O H C C H H C C H C C Cl C C C O H H H H H H H H Molecule 1 Molecule 2 Molecule 3 H H H H H3C H H C N H C N C C C C H Cl H H H H Molecule 4 Molecule 5 Molecule 6 a) Identify a molecule that contains a carbonyl functional group. [1…
    Organic chemistry
  2. Q7 · 2024 QCAA · Paper 2 · 4 marks
    QUESTION 7  (4 marks) Polylactic acid (PLA) is a biodegradable plastic that can be decomposed by microorganisms into carbon dioxide (CO2), water and biomass. O CH3 CH3 OH O O n HO CH3 O O Polylactic acid a) Explain how the biodegradability of polylactic acid is related to its structure. [2 marks] b) Describe, using a diagram, the structural formula of lact…
    Polymers and biomolecules
  3. Q8 · 2024 QCAA · Paper 2 · 2 marks
    QUESTION 8  (2 marks) In the aqueous solution of a chromate salt, an equilibrium exists between the yellow chromate ions and the orange dichromate ions. This equilibrium can be represented by the equation shown. 2− Explain, at an atomic level, why no colour change occurs once the chromate–dichromate solution has established equilibrium.
    Chemical equilibrium
  4. Q1 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 1 In a chemical equation at equilibrium, a reversible arrow ( ) symbolises that (A) the forward reaction has stopped but can be reversed. (B) the moles of reactants and products present are equal. (C) half of the reactants have been converted into products. (D) the concentration of reactants and products remains constant.
    Chemical equilibrium
  5. Q2 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 2 Determine which expression represents the hydrogen ion (H+) concentration at a pH of 8.4. (A) 1 × 10-8.4 (B) 1 × 10-5.6 (C) 1 × 10-0.9 (D) 1 × 10-0.8
    Acids, bases and titration
  6. Q3 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 3 Two 0.1 M acidic solutions, X and Y, are 100% dissociated. Solution X has an electrical conductivity approximately twice that of solution Y. Identify solutions X and Y. Solution X Solution Y (A) HCl CH3COOH (B) HNO3 H2SO4 (C) H3PO4 HNO3 (D) H2SO4 HCl
    Acids, bases and titration
  7. Q4 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 4–5 Questions 4–5 refer to the decomposition of hydrogen iodide gas (HI) to produce hydrogen gas (H2) and iodine gas (I2) in a sealed 1-litre container. ∆H  =  + 53.6 kJ mol-1 2HI(g) H2(g) I2(g) + Colourless Colourless Purple QUESTION 4 Identify which change would shift the system from light purple to dark purple. (A) adding HI(g) (B) adding a ca…
    Chemical equilibrium
  8. Q5 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 4–5 Questions 4–5 refer to the decomposition of hydrogen iodide gas (HI) to produce hydrogen gas (H2) and iodine gas (I2) in a sealed 1-litre container. ∆H  =  + 53.6 kJ mol-1 2HI(g) H2(g) I2(g) + Colourless Colourless Purple QUESTION 5 Determine the equilibrium expression (Kc ) for the reaction. [ ][ ] H I 2 2 (A) K = c [ ] 2 HI [ ][ ] H I 2 2 (B)…
    Chemical equilibrium
  9. Q6 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 6 Identify the reactants that undergo a condensation reaction to produce the molecule shown. O H3C CH2 CH2 CH2 CH2 CH3 C N H (A) 1-butanol and propanamine (B) 1-propanol and butanamine (C) butanoic acid and propanamine (D) propanoic acid and butanamine
    Organic chemistry
  10. Q7 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 7 Determine which half-cell produces the largest potential difference when joined with a Zn(s) | Zn2+(aq) half-cell to form a galvanic cell. (A) Mg(s) | Mg2+(aq) (B) Cu2+(aq) | Cu(s) (C) H+(aq) | H2(g) (D) F2(g) | F-(aq)
    Redox and electrochemistry
  11. Q8 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 8 Identify the species being reduced in the equation. Br2(l) + Sn2+(aq)  →  Sn4+(aq) + 2Br-(aq) (A) Br2(l) (B) Br-(aq) (C) Sn2+(aq) (D) Sn4+(aq)
    Redox and electrochemistry
  12. Q9 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 9–10 Questions 9–10 refer to the titration curve shown, which is produced when 60.00 mL of an unknown monoprotic acid solution is titrated with 0.10 M NaOH(aq). 14.0 12.0 10.0 8.0 Equivalence point pH = 7 pH 6.0 4.0 2.0 0.0 0 10 20 30 40 50 60 0.10 M NaOH added (mL) QUESTION 9 Compared to 0.10 M NaOH, the unknown monoprotic acid is more (A) dilute…
    Acids, bases and titration
  13. Q10 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 9–10 Questions 9–10 refer to the titration curve shown, which is produced when 60.00 mL of an unknown monoprotic acid solution is titrated with 0.10 M NaOH(aq). 14.0 12.0 10.0 8.0 Equivalence point pH = 7 pH 6.0 4.0 2.0 0.0 0 10 20 30 40 50 60 0.10 M NaOH added (mL) QUESTION 10 Determine the concentration of the unknown acid. (A) 0.05 M (B) 0.10…
    Acids, bases and titration
  14. Q11 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 11 The plating of silver is conducted during the operation of the electrochemical cell shown. Voltage + − source Ag+ Spoon Ag+ Silver AgNO3(aq) Determine which statement is true for this electrochemical cell. (A) The spoon acts as the cathode. (B) The silver electrode has a negative charge. (C) The silver ions in the solution are oxidised at the…
    Redox and electrochemistry
  15. Q12 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 12 Enzymes are classified as (A) carbohydrates. (B) proteins. (C) starches. (D) lipids.
    Polymers and biomolecules
  16. Q13 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 13 Identify the reaction used to produce methanol and triglycerides. (A) oxidation (B) substitution (C) saponification (D) transesterification
    Organic chemistry
  17. Q14 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 14 Identify which molecule has the lowest boiling point. (A) butanone (B) hexanone (C) pentanone (D) propanone
    Organic chemistry
  18. Q15 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 15 - , (HCO ) Predict how a buffer solution, consisting of carbonic acid (H2CO3) and hydrogen carbonate ions 3 would react to resist a change in pH when a small amount of hydrochloric acid is added. + 2 + - - H CO (aq) HCO (aq) + H (aq) CO (aq) + 2H (aq)   2 3 3 3 (A) Equilibrium shifts to the right and the [H +](aq) increases. 2 - [CO ](aq) (B)…
    Acids, bases and titration
  19. Q16 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 16 Haloalkanes undergo a substitution reaction with cyanide (CN- ) in ethanol to produce (A) alkanes. (B) amines. (C) nitriles. (D) esters.
    Organic chemistry
  20. Q17 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 17–18 Questions 17–18 refer to the reaction shown. O H+ R C O H H O R H O H Product X + + Carboxylic acid Alcohol Water QUESTION 17 Determine the functional group present in Product X. (A) ester (B) ketone (C) alcohol (D) aldehyde
    Organic chemistry
  21. Q18 · 2023 QCAA · Paper 1 · 1 mark
    QUESTIONS 17–18 Questions 17–18 refer to the reaction shown. O H+ R C O H H O R H O H Product X + + Carboxylic acid Alcohol Water QUESTION 18 Identify the reaction used to produce X. (A) addition (B) hydration (C) condensation (D) hydrogenation
    Organic chemistry
  22. Q19 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 19 Identify the polymer shown. CH3 CH CH2 n (A) polyethene (B) polypeptide (C) polypropene (D) polysaccharide
    Polymers and biomolecules
  23. Q20 · 2023 QCAA · Paper 1 · 1 mark
    QUESTION 20 The structural formula for a polypeptide is shown. O O H N H H O N H H N O H O O S H Identify the three amino acids present from left to right. (A) Arg, Cys, Met (B) Asp, Cys, Ala (C) Glu, Cys, Asp (D) Ile, Cys, Gly
    Polymers and biomolecules
  24. Q21 · 2023 QCAA · Paper 1 · 4 marks
    QUESTION 21  (4 marks) CO(g) reacts with O2(g) in a sealed container producing CO2(g) to reach equilibrium. 2CO(g) + O2(g) 2CO2(g) Apply collision theory to explain how increasing the concentration of O2 at equilibrium will affect the concentration of CO2 if the temperature and volume are held constant.
    Chemical equilibrium