IB Questionbank Chemistry11.The equilibrium between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4, is shown below.2NO2(g) N2O4(g)Kc = 0.01What happens when the volume of a mixture at equilibrium is decreased at a constant temperature?I.The value of Kc increasesII.More N2O4 is formedIII.The ratio of decreasesA.I and II onlyB.I and III onlyC.II and III onlyD.I, II and III(Total 1 mark) 2.Which statement about chemical equilibria implies they are dynamic?A.The position of equilibrium constantly changes.B.The rates of forward and backward reactions change.C.The reactants and products continue to react.D.The concentrations of the reactants and products continue to change.(Total 1 mark) 3.Methanol may be produced by the exothermic reaction of carbon monoxide gas and hydrogen gas.CO(g) + 2H2(g) CH3OH(g)HO = 103 kJ(a)State the equilibrium constant expression, Kc, for the production of methanol.............................................................................................................................................................................................................................................................................(1) (b)State and explain the effect of changing the following conditions on the amount of methanol present at equilibrium:(i)increasing the temperature of the reaction at constant pressure.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (ii)increasing the pressure of the reaction at constant temperature.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (c)The conditions used in industry during the production of methanol are a temperature of 450 C and pressure of up to 220 atm. Explain why these conditions are used rather than those that could give an even greater amount of methanol.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(d)A catalyst of copper mixed with zinc oxide and alumina is used in industry for this production of methanol. Explain the function of the catalyst.............................................................................................................................................................................................................................................................................(1)(Total 8 marks) 4.Which is the correct relationship between enthalpy of vaporization, intermolecular forces and boiling point?Enthalpy of vaporizationIntermolecular forcesBoiling pointA.smallweakhighB.smallstronglowC.largeweakhighD.largestronghigh(Total 1 mark) .................................................................................................................................................................................................................................................................................................................................................................................(2)(c)The conditions used in industry during the production of methanol are a temperature of 450 C and pressure of up to 220 atm. Explain why these conditions are used rather than those that could give an even greater amount of methanol.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (d)A catalyst of copper mixed with zinc oxide and alumina is used in industry for this production of methanol. Explain the function of the catalyst.............................................................................................................................................................................................................................................................................(1)(Total 8 marks) 5.For the following reaction Kc = 1.0 105 at 30 C.2NOCl(g) 2NO(g) + Cl2(g)Which relationship is correct at equilibrium at this temperature?A.The concentration of NO equals the concentration of NOCl.B.The concentration of NOCl is double the concentration of Cl2.C.The concentration of NOCl is much greater than the concentration of Cl2.D.The concentration of NO is much greater than the concentration of NOCl.(Total 1 mark)6.The reaction below represents the Haber process for the industrial production of ammonia.N2(g) + 3H2(g) 2NH3(g)HO = 92 kJThe optimum conditions of temperature and pressure are chosen as a compromise between those that favour a high yield of ammonia and those that favour a fast rate of production. Economic considerations are also important.Which statement is correct?A.A higher temperature would ensure higher yield and a faster rate.B.A lower pressure would ensure a higher yield at a lower cost.C.A lower temperature would ensure a higher yield and a faster rate.D.A higher pressure would ensure a higher yield at a higher cost.(Total 1 mark) 7.An example of a homogeneous reversible reaction is the reaction between hydrogen and iodine.H2(g) + I2(g) 2HI(g)(i)Outline the characteristics of a homogeneous chemical system that is in a state of equilibrium.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (ii)Deduce the expression for the equilibrium constant, Kc.............................................................................................................................................................................................................................................................................(1)(iii)Predict what would happen to the position of equilibrium and the value of Kc if the pressure is increased from 1 atm to 2 atm.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (iv)The value of Kc at 500 K is 160 and the value of Kc at 700 K is 54. Deduce what this information tells us about the enthalpy change of the forward reaction.............................................................................................................................................................................................................................................................................(1) (v)The reaction can be catalysed by adding platinum metal. State and explain what effect the addition of platinum would have on the value of the equilibrium constant.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 8 marks)8.Which statement is correct for a crystal of iron(II) sulfate in a state of equilibrium with a saturated solution of iron(II) sulfate?A.The colour of the solution darkens as the crystal continues to dissolve.B.The concentration of the iron(II) sulfate solution increases as the water evaporates.C.The shape of the iron(II) sulfate crystal does not change.D.The colour of the solution does not change but the shape of the crystal may change.(Total 1 mark) 9.(i)A state of equilibrium can exist when a piece of copper metal is placed in a solution of copper(II) sulfate. Outline the characteristics of a chemical system in dynamic equilibrium.(2) (ii)For an exothermic reaction state how an increase in temperature would affect both Kc and the position of equilibrium.(2)(Total 4 marks)10.Consider the equilibrium between methanol, CH3OH(l), and methanol vapour, CH3OH(g).CH3OH(l) CH3OH(g)What happens to the position of equilibrium and the value of Kc as the temperature decreases?Position of equilibriumValue of KcA.shifts to the leftdecreasesB.shifts to the leftincreasesC.shifts to the rightdecreasesD.shifts to the rightincreases(Total 1 mark) 11.(a)The production of ammonia is an important industrial process.N2(g) + 3H2(g) 2NH3(g) (i)Using the average bond enthalpy values in Table 10 of the Data Booklet, determine the standard enthalpy change for this reaction.(3) (ii)The standard entropy values, S, at 298 K for N2(g), H2(g) and NH3(g) are 193, 131 and 192 JK1 mol1 respectively. Calculate SO for the reaction and with reference to the equation above, explain the sign of SO.(4) (iii)Calculate GO for the reaction at 298 K.(1) (iv)Describe and explain the effect of increasing temperature on the spontaneity of the reaction.(2) (b)The reaction used in the production of ammonia is an equilibrium reaction. Outline the characteristics of a system at equilibrium.(2) (c)Deduce the equilibrium constant expression, Kc, for the production of ammonia.(1) (d)(i)0.20 mol of N2(g) and 0.20 mol of H2(g) were allowed to reach equilibrium in a 1dm3 closed container. At equilibrium the concentration of NH3(g) was 0.060moldm3. Determine the equilibrium concentrations of N2(g) and H2(g) and calculate the value of Kc.(3) (ii)Predict and explain how increasing the temperature will affect the value of Kc.(2) (e)Describe how increasing the pressure affects the yield of ammonia.(2) (f)In practice, typical conditions used in the Haber process are a temperature of 500 C and a pressure of 200 atmospheres. Outline why these conditions are used rather than those that give the highest yield.(2) (g)A catalyst of iron is used in the Haber process. State and explain how the catalyst affects Kc and the position of equilibrium.(3)(Total 25 marks)12.What is the equilibrium constant expression, Kc, for the following reaction?N2O4(g) 2NO2(g)A.Kc = B.Kc = C.Kc = D.Kc = [NO2][N2O4]2(Total 1 mark) ??800(ii)Predict and explain how increasing the temperature will affect the value of Kc.(2) (e)Describe how increasing the pressure affects the yield of ammonia.(2) (f)In practice, typical conditions used in the Haber process are a temperature of 500 C and a pressure of 200 atmospheres. Outline why these conditions are used rather than those that give the highest yield.(2) (g)A catalyst of iron is used in the Haber process. State and explain how the catalyst affects Kc and the position of equilibrium.(3)(Total 25 marks)13.Consider the endothermic reaction below.5CO(g) + I2O5(g) 5CO2(g) + I2(g)According to Le Chateliers principle, which change would result in an increase in the amount of CO2?A.Increasing the temperatureB.Decreasing the temperatureC.Increasing the pressureD.Decreasing the pressure(Total 1 mark) B.Kc = ??800(ii)Predict and explain how increasing the temperature will affect the value of Kc.(2) (e)Describe how increasing the pressure affects the yield of ammonia.(2) (f)In practice, typical conditions used in the Haber process are a temperature of 500 C and a pressure of 200 atmospheres. Outline why these conditions are used rather than those that give the highest yield.(2) (g)A catalyst of iron is used in the Haber process. State and explain how the catalyst affects Kc and the position of equilibrium.(3)(Total 25 marks)14.In carbonated drinks containing dissolved carbon dioxide under high pressure, the following dynamic equilibrium exists.CO2(aq) CO2(g)Describe the effect of opening a carbonated drink container and outline how this equilibrium is affected.(Total 2 marks) 15.0.50 mol of I2(g) and 0.50 mol of Br2(g) are placed in a closed flask. The following equilibrium is established.I2(g) + Br2(g) IBr(g)The equilibrium mixture contains 0.80 mol of IBr(g). What is the value of Kc?A.0.64B.1.3C.2.6D.64(Total 1 mark)008 T 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.Kc = 16.The Haber process enables the large-scale production of ammonia needed to make fertilizers.The equation for the Haber process is given below.N2(g) + 3H2 2NH3(g)The percentage of ammonia in the equilibrium mixture varies with temperature. (i)Use the graph to deduce whether the forward reaction is exothermic or endothermic and explain your choice.(2) (ii)State and explain the effect of increasing the pressure on the yield of ammonia.(2)(iii)Explain the effect of increasing the temperature on the rate of reaction.(2)(Total 6 marks) 17.What is the effect of an increase of temperature on the yield and the equilibrium constant for the following reaction?2H2(g) + CO(g) CH3OH(l)HO = 128 kJYieldEquilibriumconstantA.IncreasesIncreasesB.IncreasesDecreasesC.DecreasesIncreasesD.DecreasesDecreases(Total 1 mark) 18.Which statements about a liquid are correct?I.When the temperature of a liquid in a closed container increases, its vapour pressure increases.II.When the pressure on a liquid increases, its boiling point increases.III.When the pressure on a liquid increases, its vapour pressure increases.A.I and II onlyB.I and III onlyC.II and III onlyD.I, II and III(Total 1 mark)19.Consider the following equilibrium reaction.2SO2(g) + O2(g) 2SO3(g)Ho = 197 kJWhich change in conditions will increase the amount of SO3 present when equilibrium is re-established?A.Decreasing the concentration of SO2B.Increasing the volumeC.Decreasing the temperatureD.Adding a catalyst(Total 1 mark) 20.Biodiesel makes use of plants ability to fix atmospheric carbon by photosynthesis.Many companies and individuals are now using biodiesel as a fuel in order to reduce their carbon footprint. Biodiesel can be synthesized from vegetable oil according to the following reaction. (a)Identify the organic functional group present in both vegetable oil and biodiesel.......................................................................................................................................(1)(b)For part of her extended essay investigation into the efficiency of the process, a student reacted a pure sample of a vegetable oil (where R = C17H33) with methanol.The raw data recorded for the reaction is below.Mass of oil=1013.0 gMass of methanol=200.0 gMass of sodium hydroxide=3.5 gMass of biodiesel produced=811.0 gThe relative molecular mass of the oil used by the student is 885.6. Calculate the amount (in moles) of the oil and the methanol used, and hence the amount (in moles) of excess methanol...............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3) (c)The reversible arrows in the equation indicate that the production of biodiesel is an equilibrium process.(i)State what is meant by the term dynamic equilibrium.......................................................................................................................................................................................................................................................(1) (ii)Using the abbreviations [vegetable oil], [methanol], [glycerol] and [biodiesel] deduce the equilibrium constant expression (Kc) for this reaction.(1) (iii)Suggest a reason why excess methanol is used in this process.......................................................................................................................................................................................................................................................(1) (iv)State and explain the effect that the addition of the sodium hydroxide catalyst will have on the position of equilibrium..................................................................................................................................................................................................................................................................................................................................................................................(2) (d)The reactants had to be stirred vigorously because they formed two distinct layers in the reaction vessel. Explain why they form two distinct layers and why stirring increases the rate of reaction.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (e)Calculate the percentage yield of biodiesel obtained in this process.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (f)When biodiesel is combusted it produces carbon dioxide. Explain why the use of biodiesel as a fuel does not significantly contribute to global warming.............................................................................................................................................................................................................................................................................(1)(Total 14 marks)21.Consider the following reversible reaction.Cr2O72(aq) + H2O(l) 2CrO42(aq) + 2H+(aq)What will happen to the position of equilibrium and the value of Kc when more H+ ions are added at constant temperature?Position of equilibriumValue of KcA.shifts to the leftdecreasesB.shifts to the rightincreasesC.shifts to the rightdoes not changeD.shifts to the leftdoes not change(Total 1 mark) 22.Consider this equilibrium reaction in a sealed container:H2O(g) H2O(l)What will be the effect on the equilibrium of increasing the temperature from 20 C to 30 C?A.More of the water will be in the gaseous state at equilibrium.B.More of the water will be in the liquid state at equilibrium.C.At equilibrium the rate of condensation will be greater than the rate of evaporation.D.At equilibrium the rate of evaporation will be greater than the rate of condensation.(Total 1 mark)23.What effect will an increase in temperature have on the Kc value and the position of equilibrium in the following reaction?N2(g) + 3H2(g) 2NH3(g)H = 92 kJKcEquilibrium positionA.increasesshifts to the rightB.decreasesshifts to the leftC.increasesshifts to the leftD.decreasesshifts to the right(Total 1 mark) 24.Which statement is always correct for a chemical reaction at equilibrium?A.The rate of the forward reaction equals the rate of the reverse reaction.B.The amounts of reactants and products are equal.C.The concentration of the reactants and products are constantly changing.D.The forward reaction occurs to a greater extent than the reverse reaction.(Total 1 mark) 25.Consider the following equilibrium.2SO2(g) + O2(g) 2SO3(g)Ho = 198 kJ mol1 (i)Deduce the equilibrium constant expression, Kc, for the reaction.(1) (ii)State and explain the effect of increasing the temperature on the yield of sulfur trioxide.(2) (iii)State the effect of a catalyst on the value of Kc.(1) (iv)State and explain the effect of a catalyst on the position of equilibrium.(2)(Total 6 marks) 26.Which statement is correct for the equilibrium H2O(l) H2O(g) in a closed system at 100C?A.All the H2O(l) molecules have been converted to H2O(g).B.The rate of the forward reaction is greater than the rate of the reverse reaction.C.The rate of the forward reaction is less than the rate of the reverse reaction.D.The pressure remains constant.(Total 1 mark) (ii)State and explain the effect of increasing the temperature on the yield of sulfur trioxide.(2) (iii)State the effect of a catalyst on the value of Kc.(1) (iv)State and explain the effect of a catalyst on the position of equilibrium.(2)(Total 6 marks)27.When a mixture of 0.100 mol NO, 0.051 mol H2 and 0.100 mol H2O were placed in a 1.0 dm3 flask at 300 K, the following equilibrium was established.2NO(g) + 2H2(g) N2(g) + H2O(g)At equilibrium, the concentration of NO was found to be 0.062 mol dm3. Determine the equilibrium constant, Kc, of the reaction at this temperature.(Total 4 marks) 28.An increase in temperature increases the amount of chlorine present in the following equilibrium.PCl5(s) PCl3(l) + Cl2(g)What is the best explanation for this?A.The higher temperature increases the rate of the forward reaction only.B.The higher temperature increases the rate of the reverse reaction only.C.The higher temperature increases the rate of both reactions but the forward reaction is affected more than the reverse.D.The higher temperature increases the rate of both reactions but the reverse reaction is affected more than the forward.(Total 1 mark) 29.What will happen when at a constant temperature, more iodide ions, I, are added to the equilibrium below?I2(s) + I(aq) I3(aq)A.The amount of solid iodine decreases and the equilibrium constant increases.B.The amount of solid iodine decreases and the equilibrium constant remains unchanged.C.The amount of solid iodine increases and the equilibrium constant decreases.D.The amount of solid iodine increases and the equilibrium constant remains unchanged.(Total 1 mark)30.Consider the following reaction taking place at 375 C in a 1.00 dm3 closed container.Cl2(g) + SO2(g) SO2Cl2(g)HO = 84.5 kJ (i)Deduce the equilibrium constant expression, Kc, for the reaction.(1) (ii)If the temperature of the reaction is changed to 300 C, predict, stating a reason in each case, whether the equilibrium concentration of SO2Cl2 and the value of Kc will increase or decrease.(3) (iii)If the volume of the container is changed to 1.50 dm3, predict, stating a reason in each case, how this will affect the equilibrium concentration of SO2Cl2 and the value of Kc.(3) (iv)Suggest, stating a reason, how the addition of a catalyst at constant pressure and temperature will affect the equilibrium concentration of SO2Cl2.(2)(Total 9 marks) 31.Which affects the equilibrium vapour pressure of a liquid in a sealed container, assuming that there is always some of the liquid present?A.The temperature of the liquidB.The surface area of the liquidC.The volume of the liquidD.The volume of the container(Total 1 mark)32.Consider the following equilibrium reaction.Cl2(g) + SO2(g) SO2Cl2(g)HO = 84.5 kJIn a 1.00 dm3 closed container, at 375 C, 8.60 103 mol of SO2 and 8.60 103 mol of Cl2 were introduced. At equilibrium, 7.65 104 mol of SO2Cl2 was formed. (i)Deduce the equilibrium constant expression, Kc, for the reaction.(1) (ii)Determine the value of the equilibrium constant, Kc.(3)(iii)If the temperature of the reaction is changed to 300 C, predict, stating a reason in each case, whether the equilibrium concentration of SO2Cl2 and the value of Kc will increase or decrease.(3) (iv)If the volume of the container is changed to 1.50 dm3, predict, stating a reason in each case, how this will affect the equilibrium concentration of SO2Cl2 and the value of Kc.(3) (v)Suggest, stating a reason, how the addition of a catalyst at constant pressure and temperature will affect the equilibrium concentration of SO2Cl2.(2)(Total 12 marks)33.The sequence of diagrams represents the system as time passes for a gas phase reaction in which reactant X is converted to product Y. Which statement is correct?A.At t = 5 days the rate of the forward reaction is greater than the rate of the backward reaction.B.At t = 7 seconds the reaction has reached completion.C.At t = 10 minutes the system has reached a state of equilibrium.D.At t = 5 days the rate of the forward reaction is less than the rate of the backward reaction.(Total 1 mark)34.What changes occur when the temperature is increased in the following reaction at equilibrium?Br2(g) + Cl2(g) 2BrCl(g)H = +14 kJ mol1Position of equilibriumValue of equilibrium constantA.Shifts towards the reactantsDecreasesB.Shifts towards the reactantsIncreasesC.Shifts towards the productsDecreasesD.Shifts towards the productsIncreases(Total 1 mark) 35.The diagrams below represent equilibrium mixtures for the reaction Y + X2 XY + X at 350K and 550 K respectively. Deduce and explain whether the reaction is exothermic or endothermic.(Total 2 marks) 36.The equation for the main reaction in the Haber process is:N2(g) + 3H2(g) 2NH3(g)H is negative (i)Determine the equilibrium constant expression for this reaction.(1) (ii)State and explain the effect on the equilibrium yield of ammonia with increasing the pressure and the temperature.(4) (iii)In practice, typical conditions used in the Haber process involve a temperature of 500C and a pressure of 200 atm. Explain why these conditions are used rather than those that give the highest yield.(2) (iv)At a certain temperature and pressure, 1.1 dm3 of N2(g) reacts with 3.3 dm3 of H2(g). Calculate the volume of NH3(g), that will be produced.(1) (v)Suggest why this reaction is important for humanity.(1) (vi)A chemist claims to have developed a new catalyst for the Haber process, which increases the yield of ammonia. State the catalyst normally used for the Haber process, and comment on the claim made by this chemist.(2)(Total 11 marks)37.For the reaction below:H2(g) + I2(g) 2HI(g)at a certain temperature, the equilibrium concentrations, in mol dm3, are[H2(g)] = 0.30, [I2(g)] = 0.30, [HI(g)] = 3.0What is the value of Kc?A.1.0102B.10C.33D.1.0102(Total 1 mark) 38.A liquid and its vapour are at equilibrium inside a sealed container. Which change will alter the equilibrium vapour pressure of the liquid in the container?A.Adding more liquidB.Adding more vapourC.Decreasing the volume of the containerD.Decreasing the temperature(Total 1 mark)