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 5 of 16

  1. Q22 · 2023 QCAA · Paper 1 · 4 marks
    QUESTION 22  (4 marks) (a) Write a balanced chemical equation to describe how polytetrafluorethene (PTFE) is produced from its monomer. [2 marks] (b) Determine whether polytetrafluorethene is an addition or condensation polymer. Explain your reasoning. [2 marks]
    Polymers and biomolecules
  2. Q23 · 2023 QCAA · Paper 1 · 6 marks
    QUESTION 23  (6 marks) The diagram represents a hydrogen fuel cell with an acid electrolyte. Anode Cathode Proton exchange membrane (−) (+) H2(g) O2(g) Product Z (a) Determine the redox half-equation occurring at the anode and cathode. [2 marks] Anode half-equation: Cathode half-equation: (b) Identify product Z. [1 mark] (c) Compare the movement of electr…
    Chemical synthesis
  3. Q24 · 2023 QCAA · Paper 1 · 5 marks
    QUESTION 24  (5 marks) R and Q are unknown transition metals from period 4 of the periodic table. Pieces of R and Q were placed separately into four 0.1 M aqueous solutions. The results are shown. 0.1 M aqueous solution Unknown metal Zn(NO3)2 Mg(NO3)2 Cu(NO3)2 AgNO3 R Coating No coating Coating Coating Q No coating No coating Coating Coating A second experim…
    Redox and electrochemistry
  4. Q25 · 2023 QCAA · Paper 1 · 7 marks
    QUESTION 25  (7 marks) During the contact process for manufacturing sulfuric acid, sulfur dioxide (SO2) and oxygen (O2) are passed over a vanadium oxide catalyst to produce sulfur trioxide (SO3). In the process, the vanadium oxide undergoes the following reactions. Reaction 1: SO2(g)  +  V2O5(s)  →  SO3(g)  +  V2O4(s) Reaction 2: 2V2O4(s)  +  O2(g)  →  2V2O5…
    Chemical synthesis
  5. Q26 · 2023 QCAA · Paper 1 · 5 marks
    QUESTION 26  (5 marks) The table shows a series of reactions that were performed to produce organic compounds A, B and C. Reaction Reactant Reagents/conditions Products 1 propanol conc. H2SO4(aq) / heat compound A and water 2 compound A H2O(g) / heat compound B and propanol H+(aq) / KMnO4(aq) / heat 3 compound B compound C (a) Determine the IUPAC name for c…
    Organic chemistry
  6. Q27 · 2023 QCAA · Paper 1 · 6 marks
    QUESTION 27  (6 marks) An unknown monoprotic acid solution was titrated with 0.1 M NaOH(aq). 14.0 12.0 10.0 8.0 pH 6.0 4.0 2.0 0.0 0.0 2.0 4.0 6.0 8.0 10.0 0.10 M NaOH added (mL) (a) Use Le Châtelier’s principle to explain why phenolphthalein is a suitable indicator for this titration. [4 marks] (b) Predict whether the pH of the equivalence point and the v…
    Acids, bases and titration
  7. Q1 · 2023 QCAA · Paper 2 · 2 marks
    QUESTION 1  (2 marks) Polylactic acid (PLA) and low-density polyethylene (LDPE) are both used to produce plastic wrapping film. Plastic Composition Density Tensile stress Elongation (%) Degradation rate (g/cm3) (MPa) PLA plant-based 1.24 60 6 slow LDPE petrochemical-based 0.92 12 148 none Analyse the data to discuss one advantage and one disadvantage of usin…
    Polymers and biomolecules
  8. Q2 · 2023 QCAA · Paper 2 · 3 marks
    QUESTION 2  (3 marks) Compare the structure of α-helix and β-pleated sheets in the secondary structure of proteins. Similarity: Difference: Significance:
    Polymers and biomolecules
  9. Q3 · 2023 QCAA · Paper 2 · 7 marks
    QUESTION 3  (7 marks) An experiment was conducted at standard state conditions to investigate the potential difference (V) produced by different galvanic cells. The three cells used in the experiment are shown. V Ag(s) graphite Salt bridge Cell 1 AgNO3 Cu(NO3)2 V graphite Mg(s) Salt bridge Cell 2 Cu(NO3)2 Mg(NO3)2 V graphite Cu(s) Salt bridge Cell 3 Cu(NO3)2…
    Redox and electrochemistry
  10. Q4 · 2023 QCAA · Paper 2 · 8 marks
    QUESTION 4  (8 marks) Compound C has the molecular formula C4H10O and is either an alcohol, an aldehyde or a carboxylic acid. Compound C infrared spectrum 0.8 Transmittance 0.6 0.4 0.2 3000 2000 1000 Wavenumber (cm–1) (a) Deduce the class of compound C. Explain your reasoning. [4 marks] (b) Deduce the structural formula and IUPAC name of two isomers of com…
    Organic analysis
  11. Q5 · 2023 QCAA · Paper 2 · 13 marks
    QUESTION 5  (13 marks) The table gives the properties of four monoprotic acids. Concentration (mol L-1) [H +] (mol L-1) Acid pH Ka 7.90 × 10-5 1 0.200 4.20 × 10-3 1.80 × 10-4 2 0.100 2.34 1.78 × 10-5 CH3COOH(aq) 0.100 1.00 × 10-2 HCl(aq) 0.010 2.00 >1 (a) Determine the relative strength of acids 1 and 2 by contrasting their Ka values. [3 marks] (b) Write a…
    Acids, bases and titration
  12. Q6 · 2023 QCAA · Paper 2 · 6 marks
    QUESTION 6  (6 marks) The reaction shows the base hydrolysis (saponification) of a triglyceride to produce glycerol and a soap. O CH2 OH CH2 O (CH2)14 CH3 C O O + + CH O (CH2)14 CH3 3NaOH CH OH 3H3C (CH2)14 ONa C C O CH2 O (CH2)14 CH3 C CH2 OH Triglyceride Soap Glycerol (a) Identify which compound in the reaction is an ester. [1 mark] (b) Contrast the stru…
    Organic chemistry
  13. Q7 · 2023 QCAA · Paper 2 · 4 marks
    QUESTION 7  (4 marks) When heated in a sealed container, solid mercury(II) oxide (HgO) decomposed to form metallic mercury (Hg) and oxygen gas (O2). 2HgO(s) 2Hg(l) O2(g) +  Orange Silver Colourless (a) Identify whether the reaction occurs in an open or closed system. [1 mark] (b) Explain why the colour of the system does not change once equilibrium is est…
    Chemical equilibrium
  14. Q8 · 2023 QCAA · Paper 2 · 7 marks
    QUESTION 8  (7 marks) Two experiments were conducted to investigate the effect of temperature on the equilibrium formed during the decomposition of hydrogen iodide (HI). 2HI(g)    H2(g) + I2(g) ∆H  =  + 53.6 kJ mol-1 Initial concentration Equilibrium concentration (mol L-1) (mol L-1) Experiment Kc [HI] [H2] [I2] [HI] [H2] [I2] 2.78 × 10−2 1 0.0…
    Chemical equilibrium
  15. Q9 · 2023 QCAA · Paper 2 · 4 marks
    QUESTION 9  (4 marks) Aspirin (C9H8O4) can be produced from a reaction between salicylic acid (C7H6O3) and acetic anhydride (C4H6O3) with ethanoic acid being a minor product. C7H6O3(s)  +  C4H6O3(aq)  →  C9H8O4(s)  +  C2H4O2(aq) Calculate the mass of salicylic acid required to produce 8.25 g of aspirin if the percentage yield of the reaction is 60%. Show you…
    Chemical synthesis
  16. Q1 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 1 Identify the type of reaction that occurs when ethene undergoes polymerisation to form polyethene. (A) addition (B) elimination (C) substitution (D) condensation
    Polymers and biomolecules
  17. Q2 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 2 Structural isomers are compounds with the same molecular formula but a different (A) molar mass. (B) molecular mass. (C) empirical formula. (D) arrangement of atoms.
    Organic chemistry
  18. Q3 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 3 Which option is true for the redox equation? Fe(s) + CuCl2(aq) → FeCl2(aq) + Cu(s) (A) Fe is oxidised and Cu is the oxidising agent (B) Fe is oxidised and Cu2+ is the oxidising agent (C) Fe2+ is oxidised and Cu is the oxidising agent (D) Fe2+ is oxidised and Cu2+ is the oxidising agent
    Redox and electrochemistry
  19. Q4 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 4 Which pair of reagents would react to form a glycosidic bond? (A) lysine and aniline (B) glucose and galactose (C) methanol and butanoic acid (D) glycerol and sodium hydroxide
    Polymers and biomolecules
  20. Q5 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 5 Phosphorus pentoxide is prepared by burning phosphorus in oxygen. P4(s) + 5O2(g) → P4O10(s) Calculate the percentage yield if 10.0 g of P4O10 is produced when 0.200 mol of P4 and 0.200 mol of O2 are reacted. (A) 2.0% (B) 3.5% (C) 17.6% (D) 88.0%
    Chemical synthesis
  21. Q6 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 6 The equilibrium concentration of A is 2.8 × 10-4 M and B is 1.2 × 10-4 M.   A g B g > 0 H Which option represents the ratio of molecules present in a sample of the gaseous mixture when the temperature is decreased and a new equilibrium established? (A) 8 molecules of A and 2 molecules of B (B) 5 molecules of A and 5 molecules of B (C) 3 mo…
    Chemical equilibrium
  22. Q7 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 7 Alcohol Compound X Compound X Amine Ester Amide Compound X in these reaction pathways is (A) a ketone. (B) an alkene. (C) an aldehyde. (D) a carboxylic acid.
    Organic chemistry
  23. Q8 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 8 Predict how the system shown will respond when a small amount of aqueous sodium hydroxide is added. + - CH COOH(aq) + H O(l) CH COO (aq) + H O (aq)  3 2 3 3 (A) Equilibrium shifts to the left and the pH decreases. (B) Equilibrium shifts to the right and the pH increases. (C) Equilibrium shifts to the left and the pH remains the same. (D) Equi…
    Chemical equilibrium
  24. Q9 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 9 H3C CH3 C C H H F Cl The IUPAC name for this molecule is (A) 2-chloro-3-fluorobutane. (B) 2-fluoro-3-chlorobutane. (C) 2-dimethyl-1-chloro-2-fluoroethane. (D) 1,2-dimethyl-1-fluoro-2-chloroethane.
    Organic chemistry