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 3 of 16

1. Q11 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 11 A BrØnsted–Lowry acid (A) accepts a proton to form its base. (B) donates a proton to form its base. (C) accepts a proton to form its conjugate base. (D) donates a proton to form its conjugate base.
   Acids, bases and titration
2. Q12 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 12 The following equilibrium law expression is given for a specific reaction. Determine which of the following is a product of this reaction. (A) CO2(g) (B) C3H8(l) (C) H2O(l) (D) O2(g)
   Chemical equilibrium
3. Q13 · 2024 QCAA · Paper 1 · 1 mark
   QUESTIONS 13–14 Questions 13–14 refer to the reactions below. Reaction 1: l4 Reaction 2: QUESTION 13 Determine the type of reaction that produced compound X. (A) addition (B) oxidation (C) substitution (D) esterification
   Organic chemistry
4. Q14 · 2024 QCAA · Paper 1 · 1 mark
   QUESTIONS 13–14 Questions 13–14 refer to the reactions below. Reaction 1: l4 Reaction 2: QUESTION 14 Identify compound Y. (A) CH3CH2CN (B) CH3CONHCH3 (C) CH3CH2CH2NH2 (D) H2NCH(CH3)COOH
   Organic chemistry
5. Q15 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 15 Identify the single displacement reaction. (A) (B) (C) (D)
   Redox and electrochemistry
6. Q16 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 16 The simplified mass spectrum for an organic compound C5HxO is shown. 43 Relative abundance 86 71 0 10 20 30 40 50 60 70 80 90 Mass-to-charge ratio (m/z) Determine which compound the mass spectrum belongs to. (A) pentan-2-one (B) pentan-3-one (C) pentan-1-ol (D) pentanal
   Organic analysis
7. Q17 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 17 Identify the product produced at the cathode when a concentrated aqueous solution of NaCl undergoes electrolysis. (A) Cl2(g) (B) Na(l) (C) O2(g) (D) H2(g)
   Redox and electrochemistry
8. Q18 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 18 The electrode and electrolyte solutions of four half-cells are shown. Half-cell Electrode Electrolyte solution (1.0 M) 1 Cu CuNO3(aq) 2 Fe Fe(NO3)2(aq) 3 Al Al(NO3)3(aq) 4 Pt Fe(NO3)3(aq) Determine which two half-cells would produce the largest potential difference (V) under standard conditions when combined to construct a voltaic cell. (A) 4 an…
   Redox and electrochemistry
9. Q19 · 2024 QCAA · Paper 1 · 1 mark
   QUESTION 19 Esters undergo hydrolysis to form a carboxylic acid and (A) water. (B) an amine. (C) an alcohol. (D) an aldehyde.
   Organic chemistry
10. Q20 · 2024 QCAA · Paper 1 · 1 mark
    QUESTION 20 Identify the polyprotic acid. (A) NH3(aq) (B) H3PO4(aq) (C) (NH4)3PO4(aq) (D) CH3COOH(aq)
    Acids, bases and titration
11. Q21 · 2024 QCAA · Paper 1 · 3 marks
    QUESTION 21  (3 marks) Reactants A and B are placed in a 1.00 L container and react to form product C. The reaction then reaches equilibrium. a) Explain why a reversible arrow ( ) is used to symbolise this reaction. [1 mark] b) Deduce whether the equilibrium for the reaction lies towards the reactants or products. Explain your reasoning. [2 marks]
    Chemical equilibrium
12. Q22 · 2024 QCAA · Paper 1 · 3 marks
    QUESTION 22  (3 marks) a) Describe the type of reaction that occurs when amino acid monomers are joined to form polypeptides. [2 marks] b) Identify the bond formed when amino acid monomers join to form a dipeptide. [1 mark]
    Polymers and biomolecules
13. Q23 · 2024 QCAA · Paper 1 · 5 marks
    QUESTION 23  (5 marks) An aqueous solution of sodium hydroxide (NaOH) was titrated against a 30.0 mL aliquot of a 0.012 M potassium hydrogen phthalate (KHP) standard aqueous solution. The balanced chemical equation for the reaction is shown. The results are shown in the titration curve. 14 12 10 8 pH 6 4 2 0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 Volume…
    Acids, bases and titration
14. Q24 · 2024 QCAA · Paper 1 · 4 marks
    QUESTION 24  (4 marks) The pKw of pure water at various temperatures was determined, to investigate the effect of temperature on the equilibrium position of self-ionisation of water. The results are shown. 15.0 14.5 14.0 13.5 pKw 13.0 12.5 12.0 11.5 11.0 0 50 100 150 200 250 Temperature (°C) Explain the effect of increasing the temperature on the pH of water…
    Acids, bases and titration
15. Q25 · 2024 QCAA · Paper 1 · 3 marks
    QUESTION 25  (3 marks) Maltose is a disaccharide formed when two monomers of α-glucose are joined. a) Identify whether α-glucose is an aldose or ketose monosaccharide. [1 mark] b) Distinguish between α-glucose and β-glucose. [2 marks]
    Polymers and biomolecules
16. Q26 · 2024 QCAA · Paper 1 · 5 marks
    QUESTION 26  (5 marks) Aqueous potassium iodate (KIO3) reacts with aqueous potassium iodide (KI) in the presence of dilute HCl(aq) to form solid iodine (I2). The overall balanced equation is shown. a) Identify the reducing agent. Explain your reasoning. [2 marks] b) Determine the reduction half-equation. [3 marks]
    Redox and electrochemistry
17. Q27 · 2024 QCAA · Paper 1 · 8 marks
    QUESTION 27  (8 marks) A series of experiments was performed to investigate the optimum reaction conditions to produce biodiesel from seed oils using a two-step process. Step 1: acid esterification using an acid catalyst (H2SO4) Step 2: transesterification using ethanol as a solvent and magnesium oxide as a nanocatalyst The experiments measured the effect of…
    Organic chemistry
18. Q28 · 2024 QCAA · Paper 1 · 4 marks
    QUESTION 28  (4 marks) One structural isomer of C4H9Cl is shown. CH3 CH3 CH2 CH Cl a) Explain why the isomer is a saturated compound. [1 mark] b) Identify whether the isomer is a primary or secondary haloalkane. [1 mark] c) Determine the structural formula of another isomer of C4H9Cl that is a tertiary haloalkane, and apply IUPAC rules to name this isome…
    Organic chemistry
19. Q29 · 2024 QCAA · Paper 1 · 3 marks
    QUESTION 29  (3 marks) Methylamine is a weak base that forms a buffer solution when mixed with methylammonium +)(aq). (CH3NH3 a) Describe, using a diagram, the structural formula of methylamine. [1 mark] Note: If you make a mistake, cancel it by ruling a single diagonal line through your work and use the
    Acids, bases and titration
20. Q1 · 2024 QCAA · Paper 2 · 3 marks
    QUESTION 1  (3 marks) A 30.00 mL aliquot of aqueous hydrochloric acid (HCl) with a pH of 2.00 was diluted with 2970.00 mL of water to make up a final volume of 3.00 L of aqueous HCl solution. a) Determine the concentration of hydrogen ions in the original 30.00 mL aliquot of HCl(aq). [1 mark] b) Calculate the pH of the final 3.00 L solution of HCl(aq). Sho…
    Acids, bases and titration
21. Q2 · 2024 QCAA · Paper 2 · 6 marks
    QUESTION 2  (6 marks) Phenol red (HIn) is a weak acid that acts as an indicator as shown. a) Identify the conjugate base of phenol red. [1 mark] b) Determine the dissociation constant (Ka) of phenol red. [1 mark] c) Explain the relationship between the pH range of colour change for phenol red and its pKa value. [4 marks]
    Acids, bases and titration
22. Q3 · 2024 QCAA · Paper 2 · 9 marks
    QUESTION 3  (9 marks) The concentration, pH and dissociation constant (Ka) of aqueous solutions of ethanoic acid and two unknown monoprotic acids, I and II, are shown. Acid Concentration (M) pH Ka 1.8 × 10−5 CH3COOH(aq) 0.2 6.6 × 10−4 I 0.2 1.9 1.3 × 106 II 0.1 1.1 a) Compare the relative strength of an aqueous solution of acid I and CH3COOH(aq). [3 marks]…
    Acids, bases and titration
23. Q4 · 2024 QCAA · Paper 2 · 11 marks
    QUESTION 4  (11 marks) Bioethanol can be synthesised from plants rich in starch. Amylose and amylopectin in the starch are converted to glucose, which then undergoes fermentation to produce ethanol. a) Explain the role of enzymes in converting the amylose and amylopectin in starch to glucose. [2 marks] b) Describe the structure of amylose and amylopectin…
    Polymers and biomolecules
24. Q5 · 2024 QCAA · Paper 2 · 8 marks
    QUESTION 5  (8 marks) The diagram shows a galvanic cell with a cell potential of 2.55 V under standard conditions. 2.55 V Cl− Na+ Metal Q electrode Mg(s) electrode Salt bridge MgSO4(aq) QSO4(aq) a) Describe the movement of electrons in the galvanic cell. [3 marks] b) Determine the half-equation and standard electrode potential for the half-cell that conta…
    Redox and electrochemistry