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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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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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