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 9 of 16

1. Q16 · 2020 QCAA · Paper 1 · 1 mark
   QUESTION 16 CH,CN + 2H, “ CH,CH,NH, The reaction shows (A) an addition reaction that converts an amine to a nitrile. (B) areduction reaction that converts a nitrile to an amine. (C) an oxidation reaction that converts an amine to a nitrile. (D) asubstitution reaction that converts a nitrile to an amine.
   Organic chemistry
2. Q17 · 2020 QCAA · Paper 1 · 1 mark
   QUESTION 17 Which of the following represents a spontaneous redox reaction with the correct standard electrode potential? Reaction E° (Vv) (A) | 2Na‘(aq) + 2Br (aq) > 2Na(s) + Bro(aq) | 3.79 (B) | Sn?*(aq) + 2Ag(s) > Sn(s) + 2Ag*(aq) -0.94 (C) | Zn(s) + CL(g) > Zn?*(aq) + 2CI (aq) 2.12 (D)_ | 2Al(s) + 3Sn?*(aq) > 2A1**(aq) + 3Sn(s)_ | 1.82
   Redox and electrochemistry
3. Q18 · 2020 QCAA · Paper 1 · 1 mark
   QUESTION 18 Solution A has a pH of 3 and solution B has a pH of 6. This indicates that solution A is (A) _ less acidic and has 0.5 times the concentration of hydrogen ions in solution B. (B) more acidic and has 2 times the concentration of hydrogen ions in solution B. (C) less acidic and has 0.001 times the concentration of hydrogen ions in solution B. (D) m…
   Acids, bases and titration
4. Q19 · 2020 QCAA · Paper 1 · 1 mark
   QUESTION 19 Dispersion forces, hydrogen bonding, disulfide bridges and ionic bonding all contribute to the (A) primary structure of proteins. (B) secondary structure of proteins. (C) tertiary structure of proteins. (D) quaternary structure of proteins.
   Polymers and biomolecules
5. Q20 · 2020 QCAA · Paper 1 · 1 mark
   Determine which of the following statements is true for the electrochemical cell shown.
   Redox and electrochemistry
6. Q21 · 2020 QCAA · Paper 1 · 5 marks
   QUESTION 21  (5 marks) a) Glucose is an example of which type of carbohydrate? [1 mark] b) Starch and cellulose are both polymers of glucose. Compare the structure of starch and cellulose in terms of their glycosidic links. [4 marks]
   Polymers and biomolecules
7. Q22 · 2020 QCAA · Paper 1 · 7 marks
   QUESTION 22  (7 marks) The structures of phenol red when in either an acidic or a basic solution are shown in the equation. p h t l r f s ed ru e n c o w hen in an acidic and a basic solution ture o the a) Identify the species that acts as the conjugate base by circling it in the equation. [1 mark] Note: If you make a mistake, draw a line through this equat…
   Acids, bases and titration
8. Q23 · 2020 QCAA · Paper 1 · 6 marks
   QUESTION 23  (6 marks) a) Identify the products of the electrolysis of i) molten sodium chloride: [1 mark] ii) dilute aqueous sodium chloride solution: [1 mark] b) Explain how the nature of the electrolyte affects the products generated when a dilute aqueous solution of sodium chloride undergoes electrolysis. [4 marks]
   Redox and electrochemistry
9. Q24 · 2020 QCAA · Paper 1 · 5 marks
   QUESTION 24  (5 marks) This table shows the effect of temperature on the pH of pure water. Temperature (°C) pH 10 7.27 15 7.17 20 7.08 25 7.00 30 6.92 50 6.63 a) Analyse the data to explain whether the self‑ionisation of water is endothermic or exothermic. Explain your reasoning. [3 marks] b) Calculate the Kw of pure water at 50 °C. Show your working. [2 m…
   Acids, bases and titration
10. Q25 · 2020 QCAA · Paper 1 · 5 marks
    QUESTION 25  (5 marks) This graph depicts the changes in concentration over time for a nitrogen dioxide / dinitrogen tetroxide gaseous equilibrium in a closed system at constant temperature. ibrium in a closed system at constant temperature ime equil in concentration over t eous e gas for roxid n tet n a it ro ge n d iox ide / din itr oge changes a) Determ…
    Chemical equilibrium
11. Q26 · 2020 QCAA · Paper 1 · 5 marks
    QUESTION 26  (5 marks) The mass and infrared spectra for an organic compound, X, with the empirical formula C5H10O, are shown. compound or f ra ct pe mas s s an o rg an ic Infrared spectrum 1.0 0.8 Relative transmittance 0.6 0.4 0.2 3000 2000 1000 Wavenumber (cm –1) Analyse the spectra to deduce the structural formula of X. Explain your reasoning.
    Organic analysis
12. Q27 · 2020 QCAA · Paper 1 · 7 marks
    QUESTION 27  (7 marks) Four unknown metals Q, X, Z and A were placed into separate test tubes containing a 0.1 M solution of their respective nitrate solutions. The results are shown in the table. Metal Q(NO3)2 solution X(NO3)2 solution Z(NO3)2 solution A(NO3)2 solution Q Not tested No reaction No reaction No reaction X Coating formed Not tested No reaction…
    Redox and electrochemistry
13. Q1 · 2020 QCAA · Paper 2 · 12 marks
    QUESTION 1  (12 marks) When zinc metal was placed into a blue solution of copper(II) nitrate, the solution became colourless and a red‑brown deposit of copper formed on the bottom of the beaker. a) Identify if the reaction that occurred can be classified as a redox reaction. Explain your reasoning. [3 marks] b) When the copper deposited in the reaction was…
    Redox and electrochemistry
14. Q2 · 2020 QCAA · Paper 2 · 12 marks
    QUESTION 2  (12 marks) Salicylic acid reacts with ethanoic anhydride in an aqueous solution to produce acetylsalicylic acid, as shown in the equation. Acetylsalicylic acid is commonly known as aspirin. O O OH CH3 C O O C CH3 H+ + + O C OH CH3 C OH CH3 C C OH O O O salicylic acid ethanoic anhydride acetylsalicylic acid ethanoic acid (C7H6O3) (C4H6O3) (C9H8O4)…
    Chemical synthesis
15. Q3 · 2020 QCAA · Paper 2 · 9 marks
    QUESTION 3  (9 marks) Ethanol can be produced by the fermentation of glucose or the hydration of ethene. a) Describe the production of ethanol by fermentation of glucose by writing a balanced equation and indicating if a catalyst is required. [3 marks] b) Calculate the atom economy for the production of ethanol by fermentation of glucose. [2 marks] Atom e…
    Chemical synthesis
16. Q4 · 2020 QCAA · Paper 2 · 10 marks
    QUESTION 4  (10 marks) Consider the organic molecule shown. H3C C CH2 H3C a) Identify the molecule as saturated or unsaturated. [1 mark] b) Apply IUPAC rules to name this molecule. [1 mark] c) Write an equation to show the products formed by the hydration of this molecule. [2 marks] d) Predict which is the major product formed in c). [1 mark] e) Identif…
    Organic chemistry
17. Q5 · 2020 QCAA · Paper 2 · 17 marks
    QUESTION 5  (17 marks) Compound A reacts with water to produce compound B and hydroxide ions. + – CH CH NH (aq) + H O(l) ƒ C H NH (aq) + OH (aq) 3 2 2 2 2 5 3 A B a) Apply IUPAC rules to name compound A. [1 mark] b) Identify the Brønsted-Lowry acids in the equation. [2 marks] c) A small amount of hydrochloric acid is added to the equilibrium mixture. Pred…
    Acids, bases and titration
18. Q1 · Original practice · 1 mark
    A sealed flask contains the equilibrium $\mathrm{N_2O_4(g)\rightleftharpoons 2NO_2(g)}$ at constant temperature. Its colour remains constant. Which statement is correct?
    Chemical equilibrium
19. Q2 · Original practice · 1 mark
    The volume of a flask containing $\mathrm{N_2(g)+3H_2(g)\rightleftharpoons2NH_3(g)}$ is suddenly halved at constant temperature. After re-equilibration, which change occurs?
    Chemical equilibrium
20. Q3 · Original practice · 1 mark
    For $\mathrm{H_2(g)+I_2(g)\rightleftharpoons2HI(g)}$, $K_c=64$. A mixture has $[\mathrm{H_2}]=0.10$, $[\mathrm{I_2}]=0.10$ and $[\mathrm{HI}]=0.40\ \mathrm{mol\,L^{-1}}$. It will initially
    Chemical equilibrium
21. Q4 · Original practice · 1 mark
    Which expression represents $K_c$ for $\mathrm{CaCO_3(s)\rightleftharpoons CaO(s)+CO_2(g)}$?
    Chemical equilibrium
22. Q5 · Original practice · 1 mark
    For $\mathrm{AgCl(s)\rightleftharpoons Ag^+(aq)+Cl^-(aq)}$, $K_{sp}=1.8\times10^{-10}$. Its molar solubility in pure water is closest to
    Chemical equilibrium
23. Q6 · Original practice · 1 mark
    At a particular temperature, $K_w=2.5\times10^{-14}$. A neutral solution at this temperature has a pH closest to
    Acids, bases and titration
24. Q7 · Original practice · 1 mark
    Which species can both accept and donate a proton in aqueous solution?
    Acids, bases and titration