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 8 of 16

1. Q25 · 2021 QCAA · Paper 1 · 5 marks
   QUESTION 25  (5 marks) 2+(aq), An equilibrium is formed between two differently coloured cobalt species, Co(H2O)6 2‒(aq), which is blue. The equation for this equilibrium is shown. which is pink, and CoCl4 2+(aq) + 4Cl–(aq)  ⇌  CoCl4 2–(aq) + 6H2O(l) Co(H2O)6 a) Apply Le Châtelier’s principle to predict the visible effect of adding AgNO3 to an 2+ and CoCl4…
   Chemical equilibrium
2. Q26 · 2021 QCAA · Paper 1 · 5 marks
   QUESTION 26  (5 marks) The graph represents changes in concentration over time for three gaseous molecules (X2, Y2 and XY) in a closed system at constant temperature and pressure. X2 + Y2 ⇌ 2XY 4 3 XY Concentration (mol L–1) X2 2 Y2 1 0 Time a) Identify whether XY is the reactant or the product. [1 mark] b) Calculate the equilibrium constant (Kc) value.…
   Chemical equilibrium
3. Q27 · 2021 QCAA · Paper 1 · 6 marks
   QUESTION 27  (6 marks) Arsenous acid, H3AsO3, reacts with nitrate ions to form arsenic acid, H3AsO4, and nitrogen dioxide. a) Determine the oxidation number of arsenic in arsenous acid. [1 mark] b) Use half-equations to balance the reaction. [4 marks] c) Determine which species is reduced in this reaction. [1 mark]
   Redox and electrochemistry
4. Q28 · 2021 QCAA · Paper 1 · 3 marks
   QUESTION 28  (3 marks) Sketch the titration curve formed when 20 mL of 0.1 M butylamine (pKa = 10.0) is titrated with 0.1 M hydrochloric acid. 14 13 12 11 10 9 8 7 pH 6 5 4 3 2 1 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 Volume (mL) Note: If you make a mistake in the sketch, cancel it by ruling a single diagonal line through your work
   Acids, bases and titration
5. Q1 · 2021 QCAA · Paper 2 · 11 marks
   QUESTION 1  (11 marks) Phosphoric acid (H3PO4) is a common triprotic acid that dissociates fully in three stages. The dissociation equations are shown in the table. Ka Stage Dissociation equation 7.1  × 10–3 1 H3PO4(aq) + H2O(l)    ⇌   H2PO4 –(aq) + H3O+(aq) 2–(aq) + H3O+(aq) 6.5 × 10–8 2 H2PO4 –(aq) + H2O(l)  ⇌  HPO4 2–(aq) + H2O(l)  ⇌  PO4 3–(aq) + H3O+(aq…
   Acids, bases and titration
6. Q2 · 2021 QCAA · Paper 2 · 10 marks
   QUESTION 2  (10 marks) Polypropene (PP) is a polymer formed from propene. Polyethylene terephthalate (PET) is a polymer formed from monomers of carboxylic acid and alcohol. A section of the PET polymer is shown. O O C C O O CH2 CH2 n a) Draw the structural formulas of the monomers used to form PET. [2 marks] i) Carboxylic acid monomer ii) Alcohol monomer N…
   Polymers and biomolecules
7. Q3 · 2021 QCAA · Paper 2 · 11 marks
   QUESTION 3  (11 marks) Four colourless liquids, A, B, C and D, are known to be butane, 1-butene, 2-butanol and 1-propanol. Reactions are carried out to identify the liquids. The results are shown. Test 1 A B C D Bromine (Br2) water No reaction No reaction No reaction Decolourised Test 2 A B C Excess acidified potassium Decolourised, Decolourised, No reaction…
   Organic chemistry
8. Q4 · 2021 QCAA · Paper 2 · 9 marks
   QUESTION 4  (9 marks) 5.00 × 10–4 moles of hydrogen gas is mixed with 1.00 × 10–3 moles of iodine vapour in a sealed 1.00 L vessel at 455.0 °C. The concentration of hydrogen iodide gas formed at equilibrium is 9.30 × 10–4 M. The balanced equation for the reaction is shown. H2(g) + I2(g)  ⇌  2HI(g) a) Write the equilibrium law expression for the reaction. [1…
   Chemical equilibrium
9. Q5 · 2021 QCAA · Paper 2 · 10 marks
   QUESTION 5  (10 marks) A sample of iron ore was tested for its iron content using the experimental procedure outlined. 8.00 g of iron Reacted with Titrated with Fe2+(aq) Fe3+(aq) ore sample H2SO4(aq) KMnO4(aq) All the iron (Fe) in the sample was converted to Fe2+(aq) by reacting it with H2SO4(aq), forming hydrogen gas. The solution made up to a final volume…
   Redox and electrochemistry
10. Q1 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 1 A partly filled water bottle is sealed and left on a bench in a room with a constant temperature. After several minutes, it is noted that the water level in the bottle remains constant. In the water bottle, the rate of evaporation is (A) less than the rate of condensation. (B) greater than the rate of condensation. (C) equal to the rate of condens…
    Chemical equilibrium
11. Q2 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 2 Mg(s) + 2Ag (aq) > 2Ag(s) + Mg”*(aq) Determine which of the following statements is true for the chemical reaction. (A) Silver ions are reduced and act as a reducing agent. (B) Silver ions are oxidised and act as a reducing agent. (C) Magnesium atoms are reduced and act as a reducing agent. (D) Magnesium atoms are oxidised and act as a reducing ag…
    Redox and electrochemistry
12. Q3 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 3 D4 N—O—* This general chemical equation represents the following type of reaction. (A) addition (B) hydrolysis (C) esterification (D) condensation
    Organic chemistry
13. Q4 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 4 Oil of wintergreen is a chemical compound with the following chemical structure. O OH Identify the functional groups present in oil of wintergreen. (A) alcohol and ester (B) alcohol and ketone (C) alcohol and aldehyde (D) alcohol and carboxylic acid
    Organic chemistry
14. Q5 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 5 The equilibrium constants of four different reactions are given. In which reaction does the equilibrium lie furthest to the left? Reaction Ke (A) | PC1,(g) + Cl,(g) = PCI,(g) 2.4 x 10! (B) | AgiO,(s) = Agt(aq) + 103 (aq) 5 1 14 1 3 9 1090 585 38 23 96.034164 3.0 5 1 14 1 3 10 1142 591 12 13 94.427597 x 5 1 14 1 3 11 1170 578 54 29 28.200943 1078 4…
    Chemical equilibrium
15. Q6 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 6 Calculate the cell potential produced by a Zn(s) | Zn**(aq) || Cu**(aq) | Cu(s) galvanic cell under standard conditions. (A) -L10V (B) -0.42V (C) +0.34V (D) +110V
    Redox and electrochemistry
16. Q7 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 7 Acid Concentration (M) pH HPO, 2.0 x 107 19 HCN 1.5 x 107 5.0 H,SO, 9.0 x 10° 1.0 CH;COOH 1.0 x 107 2.8 Analyse the experimental data to determine the relative strength of the acids from strongest to weakest. (A) H,SO, > H;PO, > HCN > CH,;,COOH (B) H,SO,> HPO, > CH,COOH > HCN (C) HCN >CH;COOH > H2SO, > H3PO, (D) HCN > CH;COOH > H;PO, > H,SO,
    Acids, bases and titration
17. Q8 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 8 An organic compound, X, reacts with sodium hydrogen carbonate to form carbon dioxide gas. Compound X is (A) an amine. (B) ahaloalkane. (C) acarboxylic acid. (D) aprimary alcohol.
    Organic chemistry
18. Q9 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 9 Phosgene gas (COCI,) is formed by the following reaction. CO(g) + Cl(g) = COCL(g) AH =-110 kJ mol! Which of the following statements is true for the system at equilibrium? (A) Removing Cl,(g) will increase the yield of phosgene and keep the K, value constant. (B) Adding a catalyst will increase the yield of phosgene and keep the K, value constant.…
    Chemical equilibrium
19. Q10 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 10 Voltage source -— Fork (cathode) Which of the following is true for the electrochemical cell? Reaction Anode Flow of electrons (A) | spontaneous oxidation From the negative terminal of the power pack, through the wire to the negative electrode. (B) | spontaneous positive electrode From the positive terminal of the power pack, through the wire and…
    Redox and electrochemistry
20. Q11 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 11 Determine the colour of a solution with a pH of 9.6 containing bromocresol green indicator. (A) pink (B) blue (C) green (D) yellow
    Acids, bases and titration
21. Q12 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 12 HN _ _/CH,— CH, H~ NH Apply IUPAC rules to name the molecule. (A) cis—2—pentene (B) trans—2—pentene (C) cis—l—ethyl-2—methylethene (D) trans—\-ethyl—2—methylethene
    Organic chemistry
22. Q13 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 13 14.00 12.00 10.00 pH of solution 8.00 IV 6.00 4.00 Il 2.00 II 0.00 0.00 0.50 1.00 1.50 2.00 Volume of NaOH added (mL) Identify the equivalence point on the titration curve. (A) I (B) I (C) Il (D) IV
    Acids, bases and titration
23. Q14 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 14 Ammonia gas reacts with oxygen gas in the following equilibrium reaction. 4NH(g) + 30(g) = 2N2(g) + 6H20(g) The equilibrium expression for the reaction is so (NHEIOS () TNgIEO] a DNallthol (®) INEJIOJ NH3}‘[03) © INPTH.0F NoP{HZO}° ©) INE OF
    Chemical equilibrium
24. Q15 · 2020 QCAA · Paper 1 · 1 mark
    QUESTION 15 HH AH HA WR WH WA A WW A AW A OR Gg a a 7 H—C—C—C—C— C—C—C—C—C=C— C—C—C—C—C—C—C—C If | | to tt df | | | | t | L ‘ow H H H H HHH 4H H H H HH HUH This compound is an unsaturated fatty acid because it contains a (A) double bond and a carboxylic acid group. (B) long carbon chain and a carboxylic acid group. (C) double bond, an aldehyde group and a hy…
    Organic chemistry