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 6 of 16

1. Q10 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 10 The midpoint of the colour change of a weak acid indicator occurs when (A) [In- ] = [H+] (B) [In- ] = [HIn] (C) [H+] = [OH- ] (D) [HIn] = [OH- ]
   Acids, bases and titration
2. Q11 · 2022 QCAA · Paper 1 · 1 mark
   QUESTIONS 11–12 These questions refer to the diagram shown. V Cu electrode Zn electrode KNO3 Salt bridge Cu2+(aq) Zn2+(aq) −(aq) NO3 −(aq) NO3 QUESTION 11 Determine the species that travels through the salt bridge towards the reduction half-cell in the electrochemical cell at standard conditions. (A) zinc ions (B) nitrate ions (C) copper ions (D) potassi…
   Redox and electrochemistry
3. Q12 · 2022 QCAA · Paper 1 · 1 mark
   QUESTIONS 11–12 These questions refer to the diagram shown. V Cu electrode Zn electrode KNO3 Salt bridge Cu2+(aq) Zn2+(aq) −(aq) NO3 −(aq) NO3 QUESTION 12 The zinc electrode (A) gains electrons and acts as the anode. (B) acts as the cathode and has a positive charge. (C) undergoes reduction and has a negative charge. (D) is oxidised and donates electrons…
   Redox and electrochemistry
4. Q13 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 13 Determine the Ka of an unknown weak acid (HA) with an aqueous concentration of 0.12 M and a pH of 3.2. (A) 5.2 × 10-3 (B) 6.3 × 10-4 (C) 3.3 × 10-6 (D) 4.0 × 10-7
   Acids, bases and titration
5. Q14 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 14 The mass spectrum for Compound X is found to have signals at the following m/z values. Mass spectrum 100 80 Relative intensity (%) 60 40 20 0 10 20 30 40 50 60 70 80 m/z Compound X is (A) butanal. (B) butanol. (C) butanone. (D) butanoic acid.
   Organic analysis
6. Q15 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 15 The structure of an amino acid is shown. O N OH NH2 HN This molecule contains an amine group and a (A) carboxyl group. (B) hydroxy group. (C) methyl group. (D) ketone group.
   Polymers and biomolecules
7. Q16 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 16 -. Determine the oxidation state of manganese in MnO4 (A) +1 (B) +2 (C) +7 (D) +8
   Redox and electrochemistry
8. Q17 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 17 Identify the redox reaction. (A) CaCO3(s) → CaO(s) + CO2(g) (B) CaO(s) + H2O(l) → Ca(OH)2(s) (C) Cl2(g) + H2O(l) → HCl(aq) + HClO(aq) (D) NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)
   Redox and electrochemistry
9. Q18 · 2022 QCAA · Paper 1 · 1 mark
   QUESTION 18 Determine the Kb expression for the weak base shown in the equilibrium equation. + - NH (aq) + H O(l) NH (aq) + OH (aq)  3 2 4 [NH ][H O] 3 2 (A) K = b + [NH ] 4 [NH ][H O] 3 2 (B) K = b - [OH ] + - [NH ][OH ] 4 (C) K = b [NH ] 3 + - [NH ][OH ] 4 (D) K = b [H O] 2
   Acids, bases and titration
10. Q19 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 19 Three voltaic cells are constructed with metal Q as one electrode and metals R, S or T as the other electrode. The potential differences for the cells are shown in the table. Voltaic cell Half-cell Half-cell Potential difference (V) Q(s) / Q2+(aq) R+(aq) / R(s) 1 1.18 Q(s) / Q2+(aq) S2+(aq) / S(s) 2 0.72 T(s) / T3+(aq) Q2+(aq) / Q(s) 3 0.95 The r…
    Redox and electrochemistry
11. Q20 · 2022 QCAA · Paper 1 · 1 mark
    QUESTION 20 CH3 CH3 ( ( 1 CH2 CH CH2 CH CH2 CH CH2 CH CH2 CH CH3 CH3 CH3 CH3 CH3 CH3 ( ( 2 CH2 CH CH2 CH CH2 CH CH2 CH CH2 CH CH3 CH3 The two forms of polypropene shown are 1 2 (A) syntactic atactic (B) isotactic atactic (C) isotactic syntactic (D) atactic syntactic
    Polymers and biomolecules
12. Q21 · 2022 QCAA · Paper 1 · 4 marks
    QUESTION 21  (4 marks) a) Identify whether 2-bromopropane is a saturated or unsaturated compound. Explain your reasoning. [2 marks] b) Determine whether 2-bromopropane is a primary, secondary or tertiary halogenoalkane. Explain your reasoning. [2 marks]
    Organic chemistry
13. Q22 · 2022 QCAA · Paper 1 · 2 marks
    QUESTION 22  (2 marks) Calculate the concentration of HF (hydrogen fluoride) in an aqueous solution with a pH of 4.00 (Ka = 7.2 × 10-4). Show your working. mol L-1 (to two significant figures) Concentration =
    Acids, bases and titration
14. Q23 · 2022 QCAA · Paper 1 · 4 marks
    QUESTION 23  (4 marks) Ibuprofen is manufactured using two different processes. Process Number Reagents Ibuprofen Waste products of Atoms Mr Atoms Mr Atoms Mr reagents used 1 7 C20H42NO10ClNa 514.5 C13H18O2 206.0 C7H24NO8ClNa 308.5 2 4 C15H22O4 266.0 C13H18O2 206.0 C2H4O2 60.0 Calculate the atom economy for each process and draw conclusions about the economi…
    Chemical synthesis
15. Q24 · 2022 QCAA · Paper 1 · 7 marks
    QUESTION 24  (7 marks) This electrochemical cell was constructed using copper and platinum electrodes. Cu(s) | Cu2+(aq) (1M) || Fe3+(aq) (1M), Fe2+(aq) (1M) | Pt(s) a) Compare the standard electrode potential (E°) of the two half-cells. [3 marks] Similarity: Difference: Significance: b) Write a balanced redox equation for the electrochemical cell. [1 mark]…
    Redox and electrochemistry
16. Q25 · 2022 QCAA · Paper 1 · 5 marks
    QUESTION 25  (5 marks) Three unknown gases are combined in a sealed flask and allowed to reach equilibrium as shown by the equation. ( ) ( ) ( ) 3A g X g 2XA g + 2 2 3 a) Determine whether the gases reach a state of dynamic equilibrium. Explain your reasoning. [3 marks] b) Determine if the relative position of equilibrium lies towards the products or react…
    Chemical equilibrium
17. Q26 · 2022 QCAA · Paper 1 · 4 marks
    QUESTION 26  (4 marks) Three unknown 0.1 M solutions, A, B and C, are found to have the following properties. [H+] (mol L-1) Solution pH pOH A 0.0001 10.0 B 2.0 C 0.063 a) Determine the pH of solution A. [1 mark] pH = (to one decimal place) b) Determine the concentration of hydrogen ions [H+] in solution B. [1 mark] mol L-1 (to two significant figures) [H+…
    Acids, bases and titration
18. Q27 · 2022 QCAA · Paper 1 · 5 marks
    QUESTION 27  (5 marks) Five colourless 0.1 M solutions of NH3, HCl, KOH, H2SO4 and CH3CH2COOH have lost their labels. The substances are randomly relabelled A, B, C, D and E. The conductivity of each solution and the colour of the solution when phenol red was added are shown. Solution Conductivity (S/m) Colour with phenol red A 4.1 yellow B 0.14 red C 0.08 y…
    Acids, bases and titration
19. Q1 · 2022 QCAA · Paper 2 · 8 marks
    QUESTION 1  (8 marks) The diagram shows a series of different reactions starting with compound A, which has the empirical formula C4H10O. H2O / H+ C and A B (alkene) H2SO4 (catalyst) at a temperature > 170 °C 2− / H+ 2− / H+ Cr2O7 Cr2O7 D E (butanoic acid) A CH3COOH / H+ F (ester) a) Identify the class of organic compounds that compound A belongs to. [1 mar…
    Organic chemistry
20. Q2 · 2022 QCAA · Paper 2 · 8 marks
    QUESTION 2  (8 marks) The reaction shows part of the contact process used to produce sulfuric acid. V O 2 5 ( ) ( ) 2SO g O 2SO g + 2 2 3 The equilibrium constant (Kc) for this reaction at different temperatures is shown. Equilibrium constant, Kc  (mol L-1) Temperature (K) 9.77 × 1025 298 8.61 × 1011 500 a) Deduce if the forward reaction is exothermic or en…
    Chemical equilibrium
21. Q3 · 2022 QCAA · Paper 2 · 9 marks
    QUESTION 3  (9 marks) A 50.0 mL solution of ethanoic acid (CH3COOH) was titrated with 15.0 mL of 0.10 M sodium hydroxide (NaOH) solution to reach the equivalence point (pKa ethanoic acid = 4.76). a) Write a balanced chemical equation to indicate how ethanoic acid acts as a Brønsted-Lowry acid during the titration and identify its conjugate base. [2 marks]…
    Acids, bases and titration
22. Q4 · 2022 QCAA · Paper 2 · 8 marks
    QUESTION 4  (8 marks) Bioethanol is a renewable energy source made from biomasses such as starch and cellulosic materials. The two-step process for the conversion of starch and cellulose to bioethanol is shown. Process Step 1 Step 2 Conversion Production to glucose process Starch Enzymatic hydrolysis Fermentation of glucose to Easier Faster (α–amylase) of st…
    Chemical synthesis
23. Q5 · 2022 QCAA · Paper 2 · 8 marks
    QUESTION 5  (8 marks) One step in the electrolytic refining of copper uses impure copper anodes and high purity copper cathodes in an electrolyte solution of copper(II) sulfate. a) Predict whether the concentration of the copper(II) sulfate solution will change during the purification process. Provide appropriate half-equations to support your reasoning. [4…
    Redox and electrochemistry
24. Q6 · 2022 QCAA · Paper 2 · 8 marks
    QUESTION 6  (8 marks) Polypeptides and proteins are formed by condensation reactions of amino acids. a) Identify the type of bond formed when three amino acids are joined to form a tripeptide and state any other product/s formed. [2 marks] b) Determine the total number of tripeptides that can be formed containing histidine, lysine and glycine and use the t…
    Polymers and biomolecules