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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 1s (A) less than the rate of condensation. (B) greater than the rate of condensation. (C) equal to the rate of condensation and equal to zero. (D) equal to the rate of condensation but not equal to zero
QUESTION 2 Mg(s) + 2Ag (aq) > 2Ag(s) + Mg* (aq) Determine which of the following statements 1s true for the chemical reaction. (A) (B) (C) (D) Silver ions are reduced and act as a reducing agent. Silver ions are oxidised and act as a reducing agent. Magnesium atoms are reduced and act as a reducing agent. Magnesium atoms are oxidised and act as a reducing agent
QUESTION 5 The equilibrium constants of four different reactions are given. In which reaction does the equilibrium lie furthest to the left? PCIs(e) + Ch(g) = PCIe) AgI0;(s) = Agt (aq) + IO; (aq) s0 x fo Cl (g) + H O() = HOCI(aq) + Cl(aq) + H*(aq) HSO; (aq) + H O(1) = H30* (aq) + SO37(aq)
QUESTION 6 Calculate the cell potential produced by a Zn(s) | Zn7*(aq) || Cu**(aq) | Cu(s) galvanic cell under standard conditions. (A) -L10V (B) -0.42V (C) +0.34V (D) +110V
QUESTION 7 oe a Analyse the experimental data to determine the relative strength of the acids from strongest to weakest. (A) H SO > H3PO > HCN > CH;COOH (B) H SO >H3PO > CH ;COOH > HCN (C) HCN > CH3COOH > H SO > H3PO 4 (D) HCN > CH3COOH > H3PO > H SO
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) (B) (C) (D) Removing Cl (g) will increase the yield of phosgene and keep the K value constant. Adding a catalyst will increase the yield of phosgene and keep the K value constant. Increasing the pressure will increase the yield of phosgene and keep the K value constant. Decreasing the temperature will decrease the yield of phosgene and keep the K value constant
QUESTION 10 Voltage source Fork (cathode) Which of the following is true for the electrochemical cell? |Reaction |Anode =| Flow |Flowofelectrons = electrons Ss ÔøΩÔøΩÔøΩ From ÔøΩÔøΩÔøΩÔøΩÔøΩ negative terminal of the power pack through the wire to the negative electrode. spontaneous positive electrode From the positive terminal of the power pack through the wire and the electrolyte to the negative electrode. (C) | non-spontaneous | negative electrode | From the negative terminal of the power pack through the wire and the electrolyte to the positive terminal. (D) | non-spontaneous | oxidation From the negative terminal of the power pack through the wire to the negative electrode.
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
QUESTION 13 14.00 12.00 10.00 8.00 6.00 pH of solution 4.00 Ill 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) I (D) IV
QUESTION 14 Ammonia gas reacts with oxygen gas in the following equilibrium reaction. 4NH (g) + 302(g) = 2N2(g) + 6H20(g) The equilibrium expression for the reaction is (A) (B) (C) (D) [NH3][05] a N ][H0] [N>][H 0] [NH3][05] [NH3]*[0 ]ÔøΩ [N2]ÔøΩ[H0]? [N2}ÔøΩ[H20]ÔøΩ [NH3]*[03}ÔøΩ
QUESTION 17 Which of the following represents a spontaneous redox reaction with the correct standard electrode potential? Eerie EY) (A) | 2NaÔøΩ(aq) + 2Br (aq) > 2Na(s) + Br>(aq) (B) | Sn**(aq) + 2Ag(s) > Sn(s) + 2AgÔøΩ(aq) (C) | Zn(s) + Cl (g) > Zn**(aq) + 2Cl (aq) 2.12 (D) | 2Al(s) + 3Sn**(aq) > 2A1ÔøΩ*(aq) + 3Sn(s)
QUESTION 18 Solution A has a pH of 3 and solution B has a pH of 6. This indicates that solution A 1s (A) (B) (C) (D) less acidic and has 0.5 times the concentration of hydrogen ions in solution B. more acidic and has 2 times the concentration of hydrogen ions in solution B. less acidic and has 0.001 times the concentration of hydrogen ions in solution B. more acidic and has 1000 times the concentration of hydrogen ions in solution B
QUESTION 20 This stimulus has not been published for copyright reasons. View electrochemical cell Figure 17.3 in OpenStax Galvanic Cells https://openstax.org/books/chemistry-2e/pages/17-2-galvanic-cells. Determine which of the following statements 1s true for the electrochemical cell. (A) Copper ions are reduced. (B) Copper is the positive electrode. (C) Electrons flow through the salt bridge. (D) Oxidation occurs on the surface of the copper
![Question-Image](https://examinsightsimages.syd1.cdn.digitaloceanspaces.com/Chemistry/Chemistry_2020_Paper_1_Question_20.webp)
Difficulty: C
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Paper 1
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2020
QUESTION 22 (7 marks) The structures of phenol red when in either an acidic or a basic solution are shown in the equation. on 0 OHÔøΩ OO am & OTs Ht Se se Yellow Red 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 equation and use the additional equation provided on page 13 of this question and response book. b) A solution of phenol red at equilibrium and 50 ÔøΩC was found to contain 2.0 x 10-4 M of the conjugate base and 0.034 M of the acid. Determine the pK for the system assuming all the protons present come from dissociation of the acid. [3 marks] (to two significant figures) c) Explain the relationship between the pH range of phenol red and its pK value. [3 marks]
QUESTION 23 (6 marks) a) Identify the products of the electrolysis of 1) molten sodium chloride: [1 mark] 1) 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]
QUESTION 24 (5 marks) This table shows the effect of temperature on the pH of pure water. Temperature (ÔøΩC) Temperature CO a) Analyse the data to explain whether the self-ionisation of water is endothermic or exothermic. Explain your reasoning. [3 marks] b) Calculate the K of pure water at 50 ÔøΩC. Show your working. [2 marks] (to three significant figures)
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. 0.120 0.100 fl = 0.080 + je) ÔøΩ & ÔøΩ 0.060 E 3 0.040 = fe) Y 0.020 0 20 40 60 80 100 120 140 160 180 200 220 Time (s) a) Determine the balanced chemical equation for the reaction in this system. [1 mark] b) Identify the time at which equilibrium is reached. [1 mark] c) Iftemperature is held constant predict the effect that doubling the volume at 100 seconds would have on the closed system by sketching the change that would occur and the approximate position of the new equilibrium on the graph. [3 marks] Note: If you make a mistake draw a line through this graph and use the additional graph provided on page 13 of this question and response book
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(NO;) solution | X(NO3) solution | Z(NO3) solution | A(NO3) solution Coating formed Coating formed Coating formed Coating formed Coating formed Not tested coating bet Poet a) Identify the species oxidised in the reaction between Z and X(NO3)p. [1 mark] b) Identify the oxidising agent in the reaction between Z and Q(NO;) . [1 mark] c) Determine the products formed from the reaction between Z and A(NO;) . [1 mark] d) Predict the standard reduction potential table for the metals Q X Z and A by listing their reduction half-equations from strongest to weakest reducing agent. Explain your reasoning. [4 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 collected and reacted with concentrated nitric acid copper(II) nitrate solution and nitrogen dioxide gas formed. Cu(s) + 4 HNO; (aq) ÔøΩ Cu(NO;) (aq) + 2 NO (g) + 2H O(1) EÔøΩ = +0.46 V 1) Determine the reduction half-equation for this reaction. [2 marks] 11) Determine the standard reduction potential EÔøΩ for the reduction half-equation. [1 mark] c) Apply your understanding of standard reduction potentials to explain why: 1) copper can dissolve in concentrated nitric acid but does not dissolve in concentrated hydrochloric acid. [3 marks] 11) NO is the gaseous product rather than H when copper dissolves in nitric acid. [3 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. a) b) Cc) d) e) O On i O C CH /&ÔøΩ CH 3 7 ÔøΩ + CÔøΩOH As = CH-CÔøΩOH I ee: CÔøΩOH 3 O salicylic acid ethanoic anhydride acetylsalicylic acid ethanoic acid (C H 05) (C H 03) (C H O0 ) (C H 0 ) Identify the type of chemical reaction used to produce aspirin. [1 mark] Write the equilibrium expression K for the reaction. [1 mark] At 20 ÔøΩC the equilibrium constant (K ) for the reaction is 2 x 10ÔøΩ. Determine whether the concentration of the reactants or products is greater at equilibrium at this temperature. [2 marks] Calculate the minimum mass of salicylic acid required to produce 500.0 mg of aspirin if the yield of aspirin 1s 45.0%. Show your working. [4 marks] mg (to three significant figures) When the reaction is heated to 40 ÔøΩC and equilibrium is re-established the concentration of acetylsalicylic acid and ethanoic acid increases. Apply Le ChatelierÔøΩs principle to predict if the forward reaction is exothermic or endothermic. Explain your reasoning. [4 marks]
QUESTION 5 (17 marks) Compound A reacts with water to produce compound B and hydroxide ions. a) b) c) d) e) CH CH NH (aq) +H O(l) f C HsNH{ (aq) + OH (aq) A B Apply IUPAC rules to name compound A. Identify the Brensted-Lowry acids in the equation. A small amount of hydrochloric acid is added to the equilibrium mixture. Predict the effect of this on the concentration of compound A in the mixture. Explain your reasoning. Calculate the pH of a 2.0 M solution of compound A. State any assumptions. Show your working. (K =5.6x10-*) (to one decimal place) Describe using a balanced chemical equation how Compound A could be made from bromomethane. Include relevant conditions and reagents in your response. [1 mark] [2 marks] [3 marks] [6 marks] [5 marks]
QUESTION 1 Melting is a (A) physical change that is reversible. (B) chemical change that is reversible. (C) physical change that is irreversible. (D) chemical change that is irreversible
QUESTION 3 Predict which product is formed at the positive electrode when a 0.1 M aqueous solution of copper(II) sulfate is electrolysed using carbon electrodes. (A) Cu(s) (B) H (g) (C) O (g) (D) SO (g)
QUESTION 5 A 10.0 M solution of ethanoic acid is best described as a (A) dilute solution of a weak acid. (B) dilute solution of a strong acid. (C) concentrated solution of a weak acid. (D) concentrated solution of a strong acid.
QUESTION 6 Which type of atoms would be more likely to gain electrons based on its position in the periodic table? (A) halogens (B) noble gases (C) alkali metals (D) alkaline earth metals
QUESTION 10 Determine which system at equilibrium will shift to the right (products) if the total pressure on the system is increased. (A) N O0 (g) = 2NO (g) (B) 2H O0(g) = 2H(g) + O2(g) (C) 2S02(g) + O(g) = 2803(g) (D) CO(g)+H O(g) = CO (g) + Hp(g)
QUESTION 14 Acid K value Nitrous acid K =4.00 x 1074 Ethanoic acid K =1.76x 10ÔøΩ Hydrofluoric acid K = 7.20 X 10-4 Chloroethanoic acid K =140x 1073 Analyse the data to determine the relative strengths of acids from strongest to weakest. (A) chloroethanoic ethanoic nitrous hydrofluoric (B) chloroethanoic hydrofluoric nitrous ethanoic (C) ethanoic nitrous hydrofluoric chloroethanoic (D) ethanoic hydrofluoric nitrous chloroethanoic
QUESTION 17 Determine the concentration of hydrogen ions (H*) in an aqueous solution containing 1.2 x 10ÔøΩ M hydroxide ions (OH ). (A) 12x10! (B) 83x10? (C) 83x10 (D) 1.2x 10ÔøΩ!ÔøΩ
QUESTION 21 ( marks) Calculate the pH of a 0.1 M aqueous solution of Ba(OH) assuming complete dissociation. Show your working. pH= (to one decimal place)
QUESTION 24 (6 marks) The cell diagram represents a voltaic cell at standard conditions. The copper solution is blue because of the presence of Cu*(aq) ions. The acidified permanganate solution is purple because of the presence of MnO (aq) ions. Half-cell Half-cell ÔøΩÔøΩÔøΩ_ ÔøΩÔøΩ____ Cu(s) | Cu** (aq) | | MnO (aq) | Pt(s) Salt bridge a) Predict which direction the electrons will flow in the voltaic cell by comparing the relative strength of the oxidising agents. Explain your reasoning. [3 marks] b) Determine the standard reduction potential EÔøΩ for the cell. [1 mark] c) Predict two qualitative observations associated with the flow of electrons and the movement of ions in the voltaic cell. [2 marks]
QUESTION 25 (5 marks) An equilibrium is formed between two differently coloured cobalt species Co(H 0) 2 * (aq) which is pink and CoCÔøΩ ~(aq) which is blue. The equation for this equilibrium is shown. a) b) Co(H 0) * (aq) + 4CI (aq) = CoC ÔøΩ (aq) + 6H 0(1) Apply Le ChatelierÔøΩs principle to predict the visible epee of adding AgNO; to an aqueous blue-coloured solution containing Co(H 0) 7* and CoClyÔøΩ ions. Explain your reasoning. When a sample of the equilibrium mixture is put into hot water the mixture turns more blue. Determine whether the forward reaction of the equation is exothermic or endothermic. Explain your reasoning. [3 marks] [2 marks]
QUESTION 26 (5 marks) The graph represents changes in concentration over time for three gaseous molecules (X Y and XY) in a closed system at constant temperature and pressure. X +Y = 2XY Concentration (mol L) Time a) Identify whether XY is the reactant or the product. [1 mark] b) Calculate the equilibrium constant (K ) value. [2 marks] (to two significant figures) c) Determine whether the position of equilibrium favours the reactants or products. Explain your reasoning. [2 marks]
QUESTION 27 (6 marks) Arsenous acid H;AsO3 reacts with nitrate ions to form arsenic acid H;AsQOy 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]
QUESTION 28 (3 marks) Sketch the titration curve formed when 20 mL of 0.1 M butylamine (pK = 10.0) is titrated with 0.1 M hydrochloric acid. 14 13 pH 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 and use the additional response space on page 17 of this question and response book
QUESTION 1 (11 marks) Phosphoric acid (H3PO ) is a common triprotic acid that dissociates fully in three stages. The dissociation equations are shown in the table. to H;PO (aq) +H 0(1) = H PO (aq) +H30*(aq) 71 x103 20 H PO (aq) +H 0(1) = HPO 2-(aq) + H30* (aq) 6.5x10ÔøΩ8 HPO 2 (aq) +H 0(1) = PO 2-(aq)-+ Hy0*(aq) 45x 1073 a) Use the information to determine the strongest Brensted-Lowry acid and its conjugate base. Explain your reasoning. [3 marks] Acid: Conjugate base: Reasoning: b) Identify an amphiprotic species from the dissociation reactions. Explain your reasoning. = /2 marks] c) Determine the Aj value for the strongest conjugate base formed when H3PO has fully dissociated. Show your working. [2 marks] Ky = (to two significant figures) d) Calculate the pH of a 0.05 M solution of dihydrogen phosphate (H PO ). Show your working and state any assumptions made. [4 marks] pH = (to one decimal place)
QUESTION 4 (9 marks) 5.00 x 1074 moles of hydrogen gas 1s mixed with 1.00 x 10> moles of iodine vapour in a sealed 1.00 L vessel at 455.0 ÔøΩC. The concentration of hydrogen iodide gas formed at equilibrium is 9.30 x 104+ M. The balanced equation for the reaction is shown. H (g)+ L(g) = 2HI(g) a) Write the equilibrium law expression for the reaction. [1 mark] b) Calculate the equilibrium constant (K ) for the reaction at 455.0 ÔøΩC. Show your working. [5 marks] (to three significant figures) c) Predict the effect that adding a catalyst would have on the reaction rates position of the equilibrium and value of K . [3 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 Fe2t (aq) Titrated with a | p 3+ ore sample H SO (aq) KMnO (aq) eed) All the iron (Fe) in the sample was converted to Fe** (aq) by reacting it with H SO (aq) forming hydrogen gas. The solution made up to a final volume of 500.0 mL. A 25.00 mL aliquot of the Fe** aqueous solution was titrated with a standardised solution of 0.0500 M KMnO . An average titre of 16.40 mL was obtained. a) Write a balanced chemical equation for the reaction between the iron (Fe) in the ore sample and sulfuric acid. [1 mark] b) Identify the species oxidised in the reaction in Question 5a). Explain your reasoning. [2 marks] c) Apply your understanding of half-equations to balance the redox equation. [2 marks] MnO (aq) + H (aq) + Fe (aq) > Mn? (aq) + H O()) + Fe? *(aq) d) Calculate the percentage of iron (Fe) in the ore sample. Show your working. [5 marks] Percentage iron (Fe) in ore sample = % (to one decimal place)
QUESTION 3 Which option is true for the redox equation? Fe(s) + CuCl (aq) ÔøΩ FeCl (aq) + Cu(s) (A) Fe is oxidised and Cu is the oxidising agent (B) Fe is oxidised and Cu? is the oxidising agent (C) Fe is oxidised and Cu is the oxidising agent (D) Fe** is oxidised and Cu?ÔøΩ is the oxidising agent
QUESTION 6 The equilibrium concentration of A is 2.8 x 10* Mand Bis 1.2 x 107 M. A(g)=B(g) AH >0 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 molecules of A and 7 molecules of B (D) 2 molecules of A and 8 molecules of B
QUESTION 8 Predict how the system shown will respond when a small amount of aqueous sodium hydroxide is added. (A) (B) (C) (D) CH;COOH(aq) + H O0(1) = CH;COOÔøΩ (aq) + H30* (aq) Equilibrium shifts to the left and the pH decreases. Equilibrium shifts to the right and the pH increases. Equilibrium shifts to the left and the pH remains the same. Equilibrium shifts to the right and the pH remains the same
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 ]
QUESTION Il Determine the species that travels through the salt bridge towards the reduction half-cell in the electrochemical cell at standard conditions. Salt bridge (A) zinc ions (B) nitrate ions (C) copper ions (D) potassium ions
QUESTION 12 The zinc electrode Cu electrode (v) KNO Salt bridge Cp \ Cu*(aq) NO; (aq) (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 to the copper ions. ET / \ ÔøΩ \ 7 S 7 2 - u- ZnÔøΩ*(aq) Zn electrode NO; (aq)
QUESTION 13 Determine the K of an unknown weak acid (HA) with an aqueous concentration of 0.12 M and a pH of 3.2. (A) 5.2x10ÔøΩ (B) 63x 107 (C) 33x 10ÔøΩ (D) 4.0x 107
QUESTION 16 Determine the oxidation state of manganese in MnO . (A) (B) (C) (D) +] +2 +7 +8
QUESTION 17 Identify the redox reaction. (A) CaCO (s) > CaO(s) + CO (g) (B) CaO(s) + H 0(1) > Ca(OH) (s) (C) CL(g) + H 0() > HCl(aq) + HC1O(aq) (D) NaOH(aq) + HCl(aq) ÔøΩ NaCl(aq) + H O(1)
QUESTION 18 Determine the K expression for the weak base shown in the equilibrium equation. NH; (aq) + HO(I) = NH (aq) + OHÔøΩ (aq) (A) x = NHaIlH20) [NH4 ] (By x ÔøΩ NUSIHO1 ÔøΩ (OH [NH *][OHÔøΩ] C) K =ÔøΩWÔøΩ OK [NH; ] (Dp) = NH IOH] [H 0]
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)/Q**(aq) | R*(aq)/ R(s) 1.18 Q(s)/Q**(aq) | S?*(aq) / S(s) 0.72 3 T(s)/T**(aq) | Q?*(aq) / Q(s) 0.95 The relative strength of the reducing agents from strongest to weakest is (A) T>Q>S>R (B) S>Q>T>R (C) R>Q>S>T (D) Q>R>T>S
QUESTION 22 (2 marks) Calculate the concentration of HF (hydrogen fluoride) in an aqueous solution with a pH of 4.00 (K =7.2 x 10). Show your working. Concentration = mol L7! (to two significant figures)
QUESTION 24 (7 marks) This electrochemical cell was constructed using copper and platinum electrodes. Cu(s) | CuÔøΩ*(aq) (1M) || Fe**(aq) (1M) Fe**(aq) (1M) | Pt(s) a) Compare the standard electrode potential (ÔøΩÔøΩ) of the two half-cells. Similarity: Difference: Significance: b) Write a balanced redox equation for the electrochemical cell. c) Determine the cell potential (in volts) for the electrochemical cell. Cell potential = V (to two significant figures) d) Determine the oxidising agent. Explain your reasoning
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;3(g) 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 reactants if the molar concentrations at equilibrium are 3.4 mol L! for A> 1.8 mol L! for X> and 4.2 mol L! for XA. Explain your reasoning. [2 marks]
QUESTION 26 (4 marks) Three unknown 0.1 M solutions A B and C are found to have the following properties. Seiten | HT mett) | pH | pOH a) Determine the pH of solution A. [1 mark] pH= (to one decimal place) b) Determine the concentration of hydrogen ions [HÔøΩ] in solution B. [1 mark] [HÔøΩ] in solution B = mol L ` (to two significant figures) c) Calculate the pOH of solution C. Show your working. [2 marks] pOH = (to one decimal place)
QUESTION 27 (5 marks) Five colourless 0.1 M solutions of NH3 HCl KOH H SO and CH;CH COOH 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 ec es ee Identify the five solutions. Explain your reasoning
QUESTION 2 (8 marks) The reaction shows part of the contact process used to produce sulfuric acid. 280; (g) +O; = 280; (g) The equilibrium constant (X ) for this reaction at different temperatures is shown. Temperature (K) | Equilibrium constant K (mol L) 298 9.77 x 107ÔøΩ 500 8.61 x 10!! a) Deduce if the forward reaction is exothermic or endothermic. Explain your reasoning. [2 marks] b) Calculate the equilibrium concentration of SO; at 500 K given the equilibrium concentrations. [SO ] = 0.860 M; [O ] = 0.330 M [2 marks] Concentration = M (to three significant figures) c) Apply Le ChatelierÔøΩs principle to explain whether halving the reaction vesselÔøΩs volume at 500 K would affect the position of the equilibrium or the value of the equilibrium constant. [4 marks]
QUESTION 3 (9 marks) A 50.0 mL solution of ethanoic acid (CH;COOH) was titrated with 15.0 mL of 0.10 M sodium hydroxide (NaOH) solution to reach the equivalence point (pK ethanoic acid = 4.76). a) b) Cc) d) Write a balanced chemical equation to indicate how ethanoic acid acts as a Bronsted-Lowry acid during the titration and identify its conjugate base. Determine the Ky of the conjugate base of ethanoic acid. (to two decimal places) Calculate the concentration of the conjugate base at the equivalence point. Show your working. Concentration = M (to three significant figures) Calculate the pH at the equivalence point. Show your working. (to one decimal place) [2 marks] [1 mark] [2 marks] [4 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 marks] b) Ifthe copper anodes contain silver and zinc impurities determine whether either metal could be produced as a by-product of the electrolytic refining of copper. Explain your reasoning. [4 marks]
QUESTION 3 Two 0.1 M acidic solutions X and Y are 100% dissociated. Solution X has an electrical conductivity approximately twice that of solution Y. Identify solutions X and Y. (A) | HCl CH ;COOH (B) | HNO H SO
QUESTION 2 Determine which expression represents the hydrogen ion (H‘) concentration at a pH of 8.4. (A) 1x 10*%*4 (B) 1x 10>° (Cc) 1x 10°? (D) 1x 10°°8
QUESTION 8 Identify the species being reduced in the equation. Br (l) + Sn**(aq) — Sn**(aq) + 2Br (aq) (A) Br (1) (B) Br (aq) (C) Sn°*(aq) (D) Sn**(aq)
QUESTION 11 The plating of silver is conducted during the operation of the electrochemical cell shown. | Voltage | _ source AgNO (aq) Determine which statement is true for this electrochemical cell. (A) The spoon acts as the cathode. (B) The silver electrode has a negative charge. (C) The silver ions in the solution are oxidised at the spoon. (D) The electrons flow from the spoon to the silver electrode.
QUESTION 5 Determine the equilibrium expression (K ) for the reaction. 2HI(g) = Hg) + L(g) Colourless Colourless Purple _ [Fo I[b] (B) K _[Ho|[h] [Hy _ 2[8)2{1) (C) K = 2[HI] » x -2HEE AH = +53.6 kJ mol!
QUESTION 21 (4 marks) CO(g) reacts with O (g) in a sealed container producing CO (g) to reach equilibrium. 2CO(g) + On(g) == 2CO2(g) Apply collision theory to explain how increasing the concentration of O at equilibrium will affect the concentration of CO if the temperature and volume are held constant.
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 oe Zn(NO3) Mg(NO3) Cu(NO3) AgNO -@[ Nocoing | Nocening | —Coving | Coming A second experiment was conducted to determine the potential difference produced by electrochemical cells constructed using metals R and Q as the electrodes. Electrochemical cell | Cathode Voltage (V) ee ee Determine the identity of metals R and Q. Explain your reasoning.
QUESTION 4 Identify which change would shift the system from light purple to dark purple. 2HI(g) = Hg) + L(g) AH = +53.6kJ mol! Colourless Colourless Purple (A) adding HI(g) (B) adding a catalyst (C) decreasing the temperature (D) increasing the concentration of H (g)
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) = H (g) + L(g) AH = +53.6kJ mol! a POD Coma On Equilibrium concentration a L 1) (mol L) K cm fn [er fm Tt [| Experiment P80 fom 900 [om fa [a0 Fons [06 [ae [oa aoe (a) Determine the concentration of HI(g) and I (g) at equilibrium for experiment 1. [2 marks] [HI]: [In]: (b) Calculate the equilibrium constant (K ) for experiment 2. Show your working. [2 marks] (c) Determine which experiment was conducted at a higher temperature. Explain your reasoning. [3 marks]
QUESTION 9 (4 marks) Aspirin (Cy)HgO ) can be produced from a reaction between salicylic acid (Cj;H O3) and acetic anhydride (C H O3) with ethanoic acid being a minor product. C7H6O03(s) + CyHe¢O3(aq) — CoHgOq(s) + C H4O>(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 your working.
QUESTION 7 (4 marks) When heated in a sealed container solid mercury(II) oxide (HgO) decomposed to form metallic mercury (Hg) and oxygen gas (O ). 2HgO(s) = 2Hg(l) + 0 (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 established. [3 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. graphite Cell 1 graphite Cell 2 graphite Cell 3 (a) Predict which cell produced the highest voltage. Explain your reasoning. [3 marks] (b) Determine the maximum voltage that could be produced by a fourth galvanic cell constructed from any of the components used in the first three cells. Use oxidation and reduction half-equations to justify your answer. [4 marks]
QUESTION 7 Determine which half-cell produces the largest potential difference when joined with a Zn(s) | Zn7*(aq) half-cell to form a galvanic cell. (A) Mg(s) | Mg**(aq) (B) Cu’*(aq) | Cu(s) (C) H*(aq) | H (g) (D) F (g)|F (aq)
QUESTION 26 (5 marks) The table shows a series of reactions that were performed to produce organic compounds A B and C. conc. H SO (aq) / heat compound A and water H O(g) / heat compound B and propanol (4) KN (a) Determine the IUPAC name for compound A. [1 mark] IUPAC name: (b) Explain one structural difference between compound B and propanol. [2 marks] (c) Deduce the structural formula of compound C. [1 mark] (d) Describe one qualitative observation that would be expected for reaction 3. [1 mark]
QUESTION 15 Predict how a buffer solution consisting of carbonic acid (H CO;) and hydrogen carbonate ions (HCO ) would react to resist a change in pH when a small amount of hydrochloric acid is added. HCO3(aq) = HCO; (aq) + H” (aq) = CO” (aq) + 2H (aq) (A) Equilibrium shifts to the right and the [H ](aq) increases. (B) Equilibrium shifts to the left and the [CO;* ](aq) increases. (C) Equilibrium shifts to the left and the [H CO; ](aq) increases. (D) Equilibrium shifts to the right and the [HCO3 ](aq) increases.
QUESTION 5 (13 marks) The table gives the properties of four monoprotic acids. (a) (b) (Cc) (d —_ (e) a 0.100 4.20 x 102 1.80 x 1074 CH COOH(aq) 0.100 ae 1.78 x 107° HCl(aq) 0.010 1.00 x 102 Determine the relative strength of acids 1 and 2 by contrasting their K values. Write a balanced chemical equation for the dissociation of ethanoic acid (CH ; COOH) in water. Identify whether the conjugate base of ethanoic acid (CH;COOH(aq)) is amphiprotic. Explain your reasoning. Calculate the pH of the aqueous solution of ethanoic acid (CH;COOH). Show your working. Determine the volume of water that would need to be added to 100.0 mL of HCl(aq) to change the pH from 2.00 to 3.00. Explain your reasoning. [3 marks] [2 marks] [2 marks] [3 marks] [3 marks]
QUESTION 10 Determine the concentration of the unknown acid. (A) (B) (C) (D) 0.05 M 0.10 M 0.20 M 0.30 M 0.10 M NaOH added (mL)
QUESTION 1 In a chemical equation at equilibrium a reversible arrow (=) symbolises that (A) the forward reaction has stopped but can be reversed. (B) the moles of reactants and products present are equal. (C) half of the reactants have been converted into products. (D) the concentration of reactants and products remains constant.
QUESTION 27 (6 marks) An unknown monoprotic acid solution was titrated with 0.1 M NaOH(aq). 0.0 2.0 4.0 6.0 8.0 10.0 0.10 M NaOH added (mL) (a) Use Le Chatelier’s principle to explain why phenolphthalein is a suitable indicator for this titration. (b) Predict whether the pH of the equivalence point and the volume of NaOH required to neutralise the acid would change if the concentration of NaOH was doubled to 0.2 M. [4 marks] [2 marks]
QUESTION 25 (7 marks) During the contact process for manufacturing sulfuric acid sulfur dioxide (SO ) and oxygen (O ) are passed over a vanadium oxide catalyst to produce sulfur trioxide (SO3). In the process the vanadium oxide undergoes the following reactions. Reaction 1: SO (g) + V 0;(s) > SO3(g) + V»O (s) Reaction 2: 2V 0 (s) + O (g) — 2V 0;(s) Overall reaction: 2SO3(g) + 05(g) —225 5 280 (g) (a) Determine the oxidation state of vanadium in V 0 (s). [1 mark] (b) Determine if vanadium in V O (s) in reaction | is acting as an oxidising or reducing agent. Explain your reasoning. [2 marks] (c) Use the reactions provided to explain why V O (s) 1s a catalyst for the overall reaction. [4 marks]
QUESTION 9 Compared to 0.10 M NaOH the unknown monoprotic acid is more 0 10 20 30 40 50 60 0.10 M NaOH added (mL) (A) dilute and weak. (B) dilute and strong. (C) concentrated and weak. (D) concentrated and strong.
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