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Chemistry Grade 11 Unit 5: CHEMICAL EQUILIBRIUM

national exam questions have come from this unit. It runs 43 pages; one careful study pass takes about 5.5 hours, and its difficulty is harder among Chemistry units. Each section below lists the questions set from it, with the year, and opens the page that teaches it.

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5.1 Introduction · read p. 222
Not asked in a national paper yet.
5.2 Chemical Equilibrium · read p. 223
Not asked in a national paper yet.
5.2.1 Reversible and Irreversible Reactions · read p. 223
  • 2017 E.C., Q5 – Which of the following factors does NOT affect the rate of a chemical reaction having solid reactants?
  • 2017 E.C., Q58 – Which statement below CORRECTLY describes the characteristics of chemical equilibrium?
  • 2016 E.C., Q8 – Which of the following explanations about reversible and irreversible reactions is CORRECT?
  • 2015 E.C., Q41 – A forward and reverse reaction continues to take place at equal rate in microscopic level without change in composition at macroscopic level. This statement is the definition of
  • 2014 E.C., Q1 – What is the difference between reversible and irreversible reactions?
  • 2012 E.C., Q12 – Which one of the following best describes chemical equilibrium?
  • 2011 E.C., Q50 – Which one of the following statements regarding a dynamic equilibrium is FALSE?
  • 2009 E.C., Q24 – Which one of the following is correct when a reaction reaches equilibrium?
  • 2006 E.C., Q6 – In a reaction, A + B product, the rate is doubled when the concentration of B is doubled, and the rate increases by a factor of 8 when the concentrations of both the reactants (A and B) are doubled, the rate law for the
  • 2006 E.C., Q21 – Which statement is true about chemical reactions at equilibrium?
  • 2005 E.C., Q26 – Which of the following statements is TRUE about equilibrium reaction?
5.2.2 Attainment and Characteristics of Chemical Equilibria · read p. 225
Not asked in a national paper yet.
5.2.3 Conditions for Attainment of Chemical Equilibria · read p. 226
Not asked in a national paper yet.
5.2.4 Equilibrium Expression and Equilibrium Constant · read p. 229
  • 2018 E.C., Q27 – If Kc1 and Kc2 are the equilibrium constants for the two reactions: XeF₆(g) + H₂O(g) ⇌ XeOF₄(g) + 2HF(g) … Kc1 and XeF₄(g) + XeF₆(g) ⇌ XeOF₄(g) + XeO₃F₂(g) … Kc2. What is the equilibrium constant for the reaction: XeF₄(g
  • 2018 E.C., Q50 – The dye bromothymol blue (HBb) is a weak acid whose ionization can be represented as follows: HBb(aq) ⇌ H⁺(aq) + Bb⁻(aq). Which way will the equilibrium shift when NaOH is added?
  • 2018 E.C., Q28 – How is the reaction quotient (Qc) related to equilibrium constant (Keq)?
  • 2017 E.C., Q25 – Consider the following equilibrium: . Which of the following changes will shift the equilibrium to the left?
  • 2017 E.C., Q57 – Consider the following equilibrium reaction at 298 K: 2NO₂(g) ⇌ N₂O₄(g) + O₂(g) P(NO₂) = 0.75 atm, P(N₂O₄) = 2.5 × 10⁻³ atm, P(O₂) = 3.5 × 10⁻⁵ atm Calculate the actual equilibrium constant, Kₚ, for this reaction. (Corre
  • 2017 E.C., Q7 – At a particular temperature, the equilibrium constant, $K_c = 0.36$ for the reaction $\mathrm{SO_3(g)} \rightleftharpoons \mathrm{SO_2(g)} + \mathrm{O_2(g)}$. Which of the following predictions can be drawn from the give
  • 2017 E.C., Q65 – Given the reaction: $\mathrm{C(s)+CO_2(g)\rightleftharpoons 2CO(g)}$ What is the equilibrium constant expression for the reaction?
  • 2016 E.C., Q39 – At a certain temperature the following reaction has an equilibrium constant Kc = 12.4. N 2 (g) + 3H 2 (g) ⇌ 2NH 3 (g) If [N 2 ] = 2.0 M, [H 2 ] = 2.0 M and [NH 3 ] = 10.0 M, to which direction will the reaction proceed t
  • 2016 E.C., Q69 – Given the following heterogeneous reaction: CaCO 3 (s) ⇌ CaO (s) + CO 2 (g) What is the equilibrium constant expression for the above reaction?
  • 2016 E.C., Q38 – Consider the following reaction: N 2 (g) + O 2 (g) = 2NO(g) The equilibrium concentrations of gaseous nitrogen, oxygen and nitrogen monoxide in a sealed container are as follows: [N 2 ] = 1 x 10 -3 M, [O 2 ] = 2 x 10 -5
  • 2015 E.C., Q36 – When a system at equilibrium is disturbed by a change of variable, the system shifts the equilibrium position in a way that tends to counteract this change of variable. This is a statement for
  • 2015 E.C., Q5 – In a kinetic experiment, a student placed crystals of iodine in a closed reaction vessel, introduced a given quantity of hydrogen gas, and collected data to calculate the rate of formation of hydrogen iodide. What would
  • 2015 E.C., Q7 – Consider this equilibrium system: CO (g) + Fe O 4 (s) ⇌ CO O 2 (g) + 3 FeO (s) Which of the following disturbances shift the equilibrium position to the right?
  • 2014 E.C., Q2 – Consider the reactions all given below are in gaseous state. For which of the following reactions is K p less than K c ?
  • 2014 E.C., Q29 – The half-life of a reaction is the time taken for the
  • 2013 E.C., Q5 – The equilibrium constant K p for the reaction 2SO 2 (g) ⇌ 2SO 3 (g) + O 2 (g) is 3.8 × 10 -3 K p at 227 °C. What is the value of K c for the reaction at the same temperature?
  • 2013 E.C., Q4 – For the reaction between gaseous NO and O 2 to for NO 2 (g), what will be the equilibrium constant expression, 2NO(g) + O 2 (g)↔ 2NO 2 (g)
  • 2013 E.C., Q36 – In the production of NH3 by the Haber process according to the equation N2(g)+3H2(g) ⇌ 2NH3(g) ΔH=-92KJ mol-1 What are the favorable conditions for the production of high yield of NH3?
  • 2013 E.C., Q65 – For a first order reaction, the concentration versus time of the reaction mixture is given by the following graph If a is the initial concentration of the reactant and if the half-life is the 1hr, after how many hours wo
  • 2013 E.C., Q3 – The law of mass action states that
  • 2013 E.C., Q1 – From the magnitude of the equilibrium constant, Keq one can deduce that
  • 2013 E.C., Q2 – The statement 'If a system at equilibrium is subjected to a stress, the system will readjust itself to reduce the effects of the stress' is known as
  • 2013 E.C., Q39 – In the production of NH3 by the Haber process according to the equation N 2 (g)+3H 2 (g) ⇌ 2NH 3 (g) ΔH=-92KJ mol -1 What are the favorable conditions for the production of high yield of NH 3 ?
  • 2012 E.C., Q39 – Under what conditions can we absolutely say a system is at equilibrium at constant temperature and pressure?
  • 2012 E.C., Q36 – Which statement is correct about the effect of adding a catalyst to a system at equilibrium? I. The rate of the forward reaction increases. II. The rate of reverse reaction increases. III. The yield of the products incre
  • 2012 E.C., Q33 – Which one is the function of iron in the Haber process?
  • 2012 E.C., Q35 – For the reaction: H2(g) + I2(g) ⇌ 2HI(g), at a certain temperature the equilibrium concentrations in mol/L are [H2]=0.2, [I2]=0.2, [HI]=2.0. Then based on this data, which one is the equilibrium constant Kc?
  • 2012 E.C., Q37 – For the reaction: N2O4(g) ⇌ 2NO2(g), Kc = 8×10^4 mol/cm^3? Actually units: 8×10^4 mol/cm^3? That is huge; likely 8×10^{-4}? Given options: [N2O4]=8×10^{-2} mol/cm^3, find [NO2]. Kc = [NO2]^2 / [N2O4] = 8×10^4? That would
  • 2011 E.C., Q35 – Which one of the following reactions at equilibrium would be unaffected by an increase in pressure? (I) N₂ (g) + ⇌ ⇌ ⇌ ⇌ 3H₂ (g) 2NH₃ (g) (II) 2H₂ (g) + O₂ (g) 2H₂O (g) (III) N₂ (g) + O₂ (g) 2NO (g) (IV) 2CO (g) + O₂ (g)
  • 2011 E.C., Q25 – $2\mathrm{X}_{(g)} \rightleftharpoons 3\mathrm{Y}_{(g)} + \mathrm{Z}_{(g)}\quad \Delta H_{(\text{forward rxn})}>0$ The molar equilibrium concentrations for the reaction mixture represented above at 298 K are $[\mathrm{X}
  • 2011 E.C., Q49 – The proposed reaction mechanism between nitrogen monoxide and bromine is give below. $\mathrm{NO}+\mathrm{Br_2}\rightleftharpoons\mathrm{NOBr_2}\ \text{(fast)}$ $\mathrm{NOBr_2}+\mathrm{NO}\to2\mathrm{NOBr}\ \text{(slow)
  • 2011 E.C., Q74 – In three different experiments the following results were obtained for the reaction A → products: [A]ₒ = 1.00 M, t₁/₂ = 50 min; [A]ₒ = 2.00 M, t₁/₂ = 25 min; [A]ₒ = 0.50 M, t₁/₂ = 100 min. What is the value of the rate c
  • 2011 E.C., Q58 – A sample of solid ammonium carbamate is heated in a closed container at 298 K and allowed to reach equilibrium. $\mathrm{NH_4CO_2NH_2\ (s) \rightleftharpoons 2\ NH_3\ (g) + CO_2\ (g)}$ If the total pressure of the system
  • 2011 E.C., Q36 – A sealed isothermal container initially contained 2 moles of CO gas and 3 moles of H₂ gas. The following reversible reaction occurred: ⇌ CO(g) + 2 H₂(g) CH₃OH(g) At equilibrium, there was 1 mole of CH₃OH in the container
  • 2011 E.C., Q66 – The reaction below takes place with all of the reactants and products in the gaseous phase. Which of the following is true of the relative rates of disappearance the reactants and appearance of the products? 2 NOCl → 2 N
  • 2010 E.C., Q32 – Given the equilibrium constant values: What is the value of for + 2 3O (g) ⇌ 2 2N (g) 2 4 O the following reaction? 1.2 ? × 10−6 2.4 × 10−6
  • 2010 E.C., Q35 – If a reaction is zero order in A, tripling the concentration of A will cause the reaction rate to:
  • 2010 E.C., Q64 – Consider the following equilibrium: $\mathrm{Cl_2(g)} + 2\mathrm{NO(g)} \rightleftharpoons 2\mathrm{NOCl(g)}$ $K_{\mathrm{eq}} = 5.0$ At equilibrium, $[\mathrm{Cl_2}] = 1.0\mathrm{M}$ and $[\mathrm{NO}] = 2.0\mathrm{M}$.
  • 2010 E.C., Q40 – For a certain gas phase reaction Which of the 25 C 0 200 C 0 following would be true if the temperature was increased from to ? I. The value of k would be smaller. II. The concentration of A(g) would be increased III. Th
  • 2010 E.C., Q30 – The equilibrium constant for the ionization of HCN is Which of the following statements is true regarding this equilibrium? (I) The reaction is product favoured. (II) The reaction is reactant favoured. (III) Equilibrium
  • 2010 E.C., Q39 – Consider the following equilibrium: $2\mathrm{CO(g)} + \mathrm{O_2(g)} \rightleftharpoons 2\mathrm{CO_2(g)}$ $K_{\mathrm{eq}} = 4.0 \times 10^{-10}$ What is the value of $K_{\mathrm{eq}}$ for $2\mathrm{CO_2(g)} \rightlef
  • 2009 E.C., Q21 – Consider the reaction What is the equilibrium constant expression if the initial concentration of , is 0.1M and the equilibrium concentration of A is expressed by x? (Assume the initial concentrations of A and B are both
  • 2009 E.C., Q54 – The second step in the production of sulphuric acid is given by the reaction: Which conditions would increase the yield of this reaction?
  • 2009 E.C., Q22 – Consider the following reaction at equilibrium. $2\mathrm{CO_2}\,(\mathrm{g}) \rightleftharpoons 2\mathrm{CO}\,(\mathrm{g}) + \mathrm{O_2}\,(\mathrm{g})\ \Delta H^0 = -514\mathrm{KJ}$ What does Le Chatelier's principle p
  • 2009 E.C., Q29 – Consider the following reactions: At a certain temperature, the rate of decomposition of is mol/s. What will be the rate of formation of ?
  • 2009 E.C., Q69 – Use the following equilibrium reaction for questions 81 What is the equilibrium expression? (M) 2[CO] K = h [C] [O ] 2 2 [CO]2
  • 2008 E.C., Q58 – In which direction will the following equilibrium shift, if a solution of is added?
  • 2008 E.C., Q36 – The rate law of the overall reaction is rate = which of the following will not increase the rate of the reaction?
  • 2008 E.C., Q52 – In which of the following systems will the position of equilibrium shift to the left upon an increase in pressure, but to the right upon an increase in temperature?
  • 2008 E.C., Q1 – A drug decomposes by zero-order kinetics with a rate constant of $2\,\mathrm{mg\,mL^{-1}\,month^{-1}}$. If the initial concentration is $100\,\mathrm{mg\,mL^{-1}}$, how long will it take for the drug to decompose by 10%?
  • 2008 E.C., Q2 – The value of for the following reaction is 0.25. What is the value of Keq at the same (g) + 2NO (g) 2 2 3 (g) + 2NO (g) ⇌2SO temperature for the reaction below?
  • 2008 E.C., Q46 – At high pressure, the following reaction is zero order, Which of the following options is (are) correct for this reaction? I. Rate of reaction = rate constant. II. Rate of reaction depends on the concentration of ammonia
  • 2008 E.C., Q53 – The hydrogen used in the Haber process is made by the following reaction $\mathrm{CH_4(g)+H_2O(g)\rightleftharpoons CO(g)+3H_2(g)}$, $\Delta H^0=+206\mathrm{KJ}$ Which of the following sets of conditions will favour the
  • 2008 E.C., Q60 – So the concentration is steady, drops sharply at time t, and settles at a lower steady value.] CH COO 3 −
  • 2007 E.C., Q66 – At 298 K the following two gaseous equilibrium involving and are established. SO (g) + 1/2 O (g) ⇌SO ; K1 2 2 3 2SO (g) ⇌2SO (g) + O (g); K2 3 2 2 Which of the following equilibrium expression is correct? 2 K = K 1 2 K =
  • 2007 E.C., Q26 – In the reaction ($2\mathrm{SO_2} + \mathrm{O_2} \rightleftharpoons 2\mathrm{SO_3}, K_{\mathrm{eq}} = 100$). What will be the concentration of $\mathrm{O_2}$, if the concentration of $\mathrm{SO_2}$ is the same as that of
  • 2007 E.C., Q25 – For the gas phase reaction $\mathrm{N_2 + O_2 \rightleftharpoons 2NO}\quad \Delta H = +180\,\mathrm{KJmol^{-1}}$ the value of K changes with the
  • 2007 E.C., Q37 – The connectional equilibrium constant expression ( ) for the system 2ICl (s) ⇌I (s) + Cl (g) 2 2 is [I ] [Cl ]/[ICl] 2 2 2 [I ][Cl ]/2[ICl] 2 2 [Cl ] 2 ([I ] + 2 [Cl ]/2[ICl] 2
  • 2007 E.C., Q58 – At , Kc for the following reaction is 0.020. 2HI (g) ⇌H (g) + I (g) 2 2 H 2 I 2 445 C 0 [H ] 2 [I ] 2 Q c A mixture of , , and HI in a vessel at has the following concentrations: [HI] = 2.0M, = 0.5M and = 0.10M, which on
  • 2006 E.C., Q34 – What is the equilibrium constant expression for the following reaction? 2 2 2
  • 2006 E.C., Q31 – Which changes will increase the amount of at equilibrium? −197kJ I. Increasing the temperature II. Decreasing the volume III. Adding a catalyst
  • 2005 E.C., Q9 – Which of the following gases is manufactured using the Haber process?
  • 2005 E.C., Q36 – Given the following equilibria and equilibrium constant: ( I ) ; K = 1.80 × 10 a −5 H CO + H O ⇌H O + HCO 2 3 2 3 + −3 K = 4.20 × 10 a −7 ( II ) ; ( III ) NH + H O ⇌H O + NH 4 + 2 3 + 3 K = 5.6 × 10 a −10 HCOOH + H O ⇌H
  • 2005 E.C., Q27 – Three gases are in equilibrium in a closed chamber sealed with a piston. The following equilibrium is established: $2\mathrm{NH_3}(\mathrm{g}) \rightleftharpoons \mathrm{N_2}(\mathrm{g}) + 3\mathrm{H_2}(\mathrm{g})$ What
  • 2005 E.C., Q68 – Which of the following reactions is expected to have negative value of entropy change ($\Delta S$)?
5.2.5 Applications of Equilibrium Constant · read p. 239
Not asked in a national paper yet.
5.2.6 Changing Equilibrium Conditions: Le-Chatelier’s Principle · read p. 245
Not asked in a national paper yet.
5.2.7 Equilibrium and Industry · read p. 253
Not asked in a national paper yet.