Free NEET Chemistry multiple-choice questions on Law of Mass Action. Attempt each question and reveal the answer with a full explanation.
For the reaction H 2(g) + I 2(g) 2HI(g) , the equilibrium constant K p changes with: Temperature Total pressure Concentration of H 2 Catalyst Given the reaction NH 4HS(s) NH 3(g) + H 2S(g) , if the partial pressure of NH 3 is x atm at equilibrium, what is the value of K p ? x 2 2x x x/2 For the reaction N 2(g) + 3H 2(g) 2NH 3(g) , the equilibrium constant is K . The equilibrium constant for the reaction NH 3(g) 1/2 N 2(g) + 3/2 H 2(g) is: 1/ K K 1/K 1/K 2 If K 1 and K 2 are the equilibrium constants for the reactions (1) N 2 + O 2 2NO and (2) NO 1/2 N 2 + 1/2 O 2 , then: K 2 = 1/ K 1 K 1 = 1/K 2 K 2 = K 1 K 1 = K 2 For the reaction CO(g) + 1 2 O 2(g) CO 2(g) , the relationship between K p and K c is given by: K p = K c(RT) -1/2 K p = K c(RT) 1/2 K p = K c(RT) K p = K c(RT) -1 If the equilibrium constant for N 2(g) + O 2(g) 2NO(g) is K , what is the equilibrium constant for 1 2 N 2(g) + 1 2 O 2(g) NO(g) ? ∘K K/2 K 2 1/K The value of K p for the reaction H 2(g) + I 2(g) 2HI(g) is 50. What is the value of K c at the same temperature? 50 25 100 50/RT For the equilibrium C(s) + CO 2(g) 2CO(g) , the partial pressures of CO 2 and CO are 2.0 and 4.0 atm respectively. K p for the reaction is: 8.0 atm 4.0 atm 2.0 atm 16.0 atm A catalyst added to a reaction at equilibrium: Does not change the equilibrium constant Increases the equilibrium constant Decreases the equilibrium constant Shifts the equilibrium to the right The equilibrium constant for the reaction A + B C + D is 10. If at a certain instant the concentrations are [A]=[B]=[C]=[D]=1 M , in which direction will the reaction proceed? Forward direction Backward direction It is at equilibrium Cannot be predicted For the reaction CO(g) + Cl 2(g) COCl 2(g) , the value of K p / K c is equal to: (RT) -1 RT (RT) -2 1.0 Which of these is least likely to act as a Lewis base? BF 3 PCl 3 OH - NH 3 The reaction quotient Q for a reaction is 1.5 10 -2 and K c is 2.0 10 -4 . In which direction will the reaction proceed? Towards the reactants Towards the products Remains at equilibrium Direction cannot be predicted What is the unit of K p for the reaction: PCl 5(g) PCl 3(g) + Cl 2(g) ? atm atm -1 atm 2 Unitless In which of the following equilibrium systems is K p < K c ? N 2(g) + 3H 2(g) 2NH 3(g) H 2(g) + I 2(g) 2HI(g) PCl 5(g) PCl 3(g) + Cl 2(g) 2NO(g) N 2(g) + O 2(g) For the equilibrium N 2O 4(g) 2NO 2(g) , if the degree of dissociation is , the total number of moles at equilibrium starting with 1 mole of N 2O 4 is: 1 + 1 - 1 + 2 2 For the reaction 2NO(g) + Cl 2(g) 2NOCl(g) , the relation between the equilibrium constants K p and K c is: K p = K c(RT) -1 K p = K c(RT) K p = K c(RT) -2 K p = K c For a reaction to be in equilibrium, the Gibbs free energy change ( G ) must be: Zero Negative Positive Infinity For the reaction C(s) + H 2O(g) CO(g) + H 2(g) , the equilibrium constant K p is 2.0 at a certain temperature. If the equilibrium partial pressure of H 2O is 0.5 atm, and those of CO and H 2 are equal, their partial pressure is: 1.0 atm 2.0 atm 0.5 atm 1.414 atm For the physical equilibrium H 2 O(l) H 2 O(g) , the equilibrium constant K p at a specific temperature is equal to: Vapour pressure of water Density of water Total atmospheric pressure Surface tension of water The relationship between standard Gibbs free energy change ( G ) and the equilibrium constant ( K ) is: G = -2.303 RT K G = RT K G = -RT K K = e G / RT The unit of the equilibrium constant K c for the reaction N 2 (g) + 3H 2 (g) 2NH 3 (g) is: L 2 mol -2 mol 2 L -2 L mol -1 Dimensionless In the reaction AlCl 3 + Cl - [AlCl 4] - , AlCl 3 acts as a: Lewis acid Lewis base Bronsted acid Bronsted base For the heterogeneous equilibrium 2C(s) + O 2 (g) 2CO(g) , the expression for K c is: [CO] 2 / [O 2 ] [CO] 2 / ([C] 2 [O 2 ]) [CO] / [O 2 ] [O 2 ] / [CO] 2 For a reaction X + Y Z , the reaction quotient Q is 10 3 at a given time. If K c = 10 5 , in which direction will the reaction proceed? Forward direction Backward direction Remains at equilibrium Cannot be predicted In which of the following reactions, the equilibrium constant K p does not have any units? H 2(g) + I 2(g) 2HI(g) PCl 5(g) PCl 3(g) + Cl 2(g) N 2(g) + 3H 2(g) 2NH 3(g) 2SO 2(g) + O 2(g) 2SO 3(g) If the concentration of A is doubled in the equilibrium A + B C , what happens to the equilibrium constant? It remains unchanged. It is doubled. It is halved. It increases by four times. The correct relationship between G and the equilibrium constant K is: G = -RT K G = RT K K = e G / RT G = G + RT K Which of the following acts as a Lewis base but not as a Bronsted base? BF 3 NH 3 H 2O None of these For which of the following reactions is the value of K p greater than K c ? PCl 5(g) PCl 3(g) + Cl 2(g) N 2(g) + 3H 2(g) 2NH 3(g) H 2(g) + I 2(g) 2HI(g) 2SO 2(g) + O 2(g) 2SO 3(g) Given the reaction NH 4Cl(s) NH 3(g) + HCl(g) . If the equilibrium pressure is P , then K p for the reaction is: P 2 / 4 P 2 4 P 2 P / 2 Consider the equilibrium HgO(s) Hg(l) + 1 2 O 2(g) . The expression for K p is: P O 2 1/2 P O 2 [Hg] P O 2 1/2 / [HgO] P O 2 2 If the equilibrium constant for N 2(g) + 3H 2(g) 2NH 3(g) is K , what is the equilibrium constant for the reaction 1 2 N 2(g) + 3 2 H 2(g) NH 3(g) ? K 1/2 K K 2 1/K The equilibrium constant for the reaction A + B 2C is K 1 . What is the equilibrium constant for the reaction C 1 2 A + 1 2 B ? 1/ K 1 K 1 1/K 1 K 1 2 For which of the following reactions, K p = K c ? H 2(g) + Br 2(g) 2HBr(g) PCl 5(g) PCl 3(g) + Cl 2(g) N 2(g) + 3H 2(g) 2NH 3(g) 2SO 2(g) + O 2(g) 2SO 3(g) For which of the following reactions is the value of K p equal to the value of K c ? H 2(g) + I 2(g) 2HI(g) PCl 5(g) PCl 3(g) + Cl 2(g) N 2(g) + 3H 2(g) 2NH 3(g) 2SO 2(g) + O 2(g) 2SO 3(g) The equilibrium constant for the reaction CO(g) + H 2O(g) CO 2(g) + H 2(g) is K . If the volume of the reaction vessel is halved, the new equilibrium constant will be: K 2K K/2 K 2 For the reaction 4NH 3(g) + 5O 2(g) 4NO(g) + 6H 2O(g) , the relationship between K p and K c is: K p = K c(RT) K p = K c(RT) -1 K p = K c(RT) 2 K p = K c The reaction quotient Q for the reaction N 2(g) + 3H 2(g) 2NH 3(g) is given by Q = [NH 3] 2 [N 2][H 2] 3 . If at a certain time Q < K c , the reaction will: Proceed in the forward direction Proceed in the backward direction Stay in equilibrium Stop completely For the reaction CO(g) + Cl2(g) <=> COCl2(g) , K p K c is equal to (RT) 2 1 RT RT RT For the reaction 2A B + C , K c = 4 10 -3 . At a given time, the composition of reaction mixture is: [A] = [B] = [C] = 2 10 -3 M . Then, which of the following is correct? Reaction is at equilibrium. Reaction has a tendency to go in forward direction. Reaction has a tendency to go in backward direction. Reaction has gone to completion in forward direction. In which of the following equilibria, K p and K c are NOT equal? PCl5(g) <=> PCl3(g) + Cl2(g) H2(g) + I2(g) <=> 2HI(g) CO(g) + H2O(g) <=> CO2(g) + H2(g) 2BrCl(g) <=> Br2(g) + Cl2(g) Given below are certain reactions. Identify the reaction for which K P K C . N2(g) + O2(g) <=> 2NO(g) H2O(g) + CO(g) <=> H2(g) + CO2(g) N2(g) + 3H2(g) <=> 2NH3(g) H2(g) + I2(g) <=> 2HI(g) For the reaction 2SO 2(g) + O 2(g) 2SO 3(g) , the value of K c is 4.0 10 4 L mol -1 . The K c for the reaction SO 3(g) SO 2(g) + 1/2 O 2(g) is: 5 10 -3 2 10 -2 2.5 10 -4 4 10 -4 For the heterogeneous equilibrium: 3Fe(s) + 4H 2O(g) Fe 3O 4(s) + 4H 2(g) , the equilibrium constant K p is represented by: K p = P H 2 4 P H 2O 4 K p = P Fe 3O 4 P H 2 4 P Fe 3 P H 2O 4 K p = P H 2 P H 2O K p = P H 2 4 P H 2O 4 In the reaction A(g) + B(g) C(g) + D(g) , the initial concentrations of A and B were 0.8 M each. At equilibrium, the concentration of C was 0.6 M . The equilibrium constant K c for the reaction is: 9 6.75 3 0.33 For which of the following reactions is K p > K c ? PCl 5(g) PCl 3(g) + Cl 2(g) N 2(g) + 3H 2(g) 2NH 3(g) 2SO 2(g) + O 2(g) 2SO 3(g) H 2(g) + I 2(g) 2HI(g) Ammonium hydrogen sulphide dissociates according to the equation NH 4HS(s) NH 3(g) + H 2S(g) . If the total pressure at equilibrium is P , the value of K p is: P 2/4 P 2 P 2/2 2P 2 For the reaction 2NOCl(g) 2NO(g) + Cl 2(g) at 400 K , K c = 3.0 10 -6 mol L -1 . The value of K p at this temperature is ( R = 0.0821 L atm K -1 mol -1 ): 9.85 10 -5 1.09 10 -4 3.0 10 -6 2.44 10 -4 The dissociation constant K a of acetic acid is 1.8 10 -5 . The degree of dissociation ( ) of 0.01 M acetic acid is: 0.042 0.42 0.018 0.0018 For the dissociation of HI , 2HI(g) H 2(g) + I 2(g) , the degree of dissociation is 0.2 at a certain temperature. If we start with 2 moles of HI , the moles of H 2 at equilibrium will be: 0.2 0.4 0.1 0.8 If the equilibrium constant for the reaction N 2(g) + O 2(g) 2NO(g) is K 1 and for the reaction 2NO(g) + O 2(g) 2NO 2(g) is K 2 , the equilibrium constant for the reaction NO 2(g) 1 2 N 2(g) + O 2(g) is: 1 K 1 K 2 1 K 1 K 2 1 2K 1 K 2 K 1 K 2 Which of the following is the correct order of Lewis acid strength for boron halides? BI 3 > BBr 3 > BCl 3 > BF 3 BF 3 > BCl 3 > BBr 3 > BI 3 BCl 3 > BF 3 > BBr 3 > BI 3 BF 3 > BI 3 > BBr 3 > BCl 3 The equilibrium constant for the reaction SO 2(g) + 1 2 O 2(g) SO 3(g) is 5 10 -2 . The equilibrium constant for 2SO 3(g) 2SO 2(g) + O 2(g) will be: 400 100 200 20 Which of the following molecules acts as a Lewis acid due to the presence of vacant d-orbitals? SiCl 4 BF 3 NH 3 AlCl 3 If the degree of dissociation of a weak acid HA is in a solution of concentration C , then according to Ostwald's dilution law, for very small : = K a C = K a C = K a C = C K a For the equilibrium reaction N 2 (g) + 3H 2 (g) 2NH 3 (g) , which of the following relations between K c and K p is correct? K c = K p (RT) 2 K p = K c (RT) 2 K p = K c (RT) -1 K c = K p RT Which of the following is the correct order of Lewis acid strength for group 13 trihalides? BCl 3 > AlCl 3 > GaCl 3 AlCl 3 > BCl 3 > GaCl 3 GaCl 3 > AlCl 3 > BCl 3 BCl 3 = AlCl 3 = GaCl 3 If the reaction quotient Q c for a reaction is 2.0 and the equilibrium constant K c is 0.5 , then: The reaction will proceed in the backward direction The reaction will proceed in the forward direction The reaction is at equilibrium The reaction will stop The equilibrium constant for H 2 (g) + I 2 (g) 2HI(g) is 50 . The equilibrium constant for HI(g) 1 2 H 2 (g) + 1 2 I 2 (g) is: 0.141 0.02 25 7.07 Which of the following equations represents the variation of the equilibrium constant K with temperature T ? K 2 K 1 = H R ( 1 T 1 - 1 T 2 ) K 2 K 1 = H R ( 1 T 2 - 1 T 1 ) K 2 K 1 = - H R ( 1 T 1 + 1 T 2 ) K 1 K 2 = H R ( 1 T 1 - 1 T 2 ) Which of the following is correct regarding Lewis acid strength? BF 3 < BCl 3 < BBr 3 BF 3 > BCl 3 > BBr 3 BF 3 = BCl 3 = BBr 3 BCl 3 > BF 3 > BBr 3 Identify the correct plot of K versus 1/T for an exothermic reaction. Straight line with a positive slope Straight line with a negative slope Hyperbola Parabola For the reaction N 2(g) + O 2(g) 2NO(g) , the equilibrium constant is K 1 . For the reaction 2NO(g) + O 2(g) 2NO 2(g) , the equilibrium constant is K 2 . The equilibrium constant K for NO 2(g) 1 2 N 2(g) + O 2(g) is: 1 / K 1 K 2 K 1 K 2 1 / (K 1 K 2) K 1 / K 2 For a reaction A + B C + D , if the equilibrium constant is 10 2 at 300 K , the standard Gibbs free energy change ( G ) is approximately: -11.5 kJ mol -1 -20.3 kJ mol -1 +11.5 kJ mol -1 -5.7 kJ mol -1 At a certain temperature, the equilibrium constant K c for the reaction SO 2(g) + NO 2(g) SO 3(g) + NO(g) is 16 . If 1 mole of each of the four gases is taken in a 1 L container, the equilibrium concentration of NO would be: 1.6 M 0.4 M 1.0 M 0.8 M For the reaction 2SO 3(g) 2SO 2(g) + O 2(g) , the unit of the equilibrium constant K c is: mol L -1 L mol -1 mol 2 L -2 Dimensionless Ammonium hydrogen sulphide dissociates as NH 4HS(s) NH 3(g) + H 2S(g) . If the total pressure at equilibrium is 2.0 atm, the value of K p is: 1.0 4.0 0.5 2.0 Which indicator is most suitable for titration between a weak base ( NH 4OH ) and a strong acid ( HCl )? Methyl orange Phenolphthalein Thymol blue None of these The units of K c for the reaction SO 2(g) + 1 2 O 2(g) SO 3(g) are: L 1/2 mol -1/2 mol 1/2 L -1/2 mol L -1 Dimensionless For the decomposition reaction PCl 5(g) PCl 3(g) + Cl 2(g) , the degree of dissociation is related to initial vapour density D and equilibrium vapour density d as: = D-d d = d-D D = D-d D = d D-d Which of the following plots correctly represents the variation of concentration with time for the reversible reaction A B starting with pure A ? Diagram showing [A] decreasing and [B] increasing until both become constant and horizontal. Diagram showing both [A] and [B] increasing over time. Diagram showing [A] and [B] crossing each other and continuing to change. Diagram showing [A] remaining constant while [B] increases linearly. Which of the following behaves as a Lewis acid in the reaction with NH 3 ? SiF 4 CH 4 C 2H 6 PH 3 For an exothermic reaction, the plot of K vs 1/T is a straight line with a: Positive slope Negative slope Zero slope Curved line Which of the following describes the relationship between K p and K c for the reaction: 2NO(g) + Cl 2(g) 2NOCl(g) ? K p = K c(RT) -1 K p = K c(RT) K p = K c K p = K c(RT) -2 Equilibrium constants K 1 and K 2 for the following equilibria : NO(g) + 1/2 O2 <=> NO2(g) and 2NO2(g) <=> 2NO(g) + O2(g) are related as - K 2 = 1 K 1 K 2 = K 1 2 K 2 = 1 K 1 2 K 2 = K 1 2 For the reaction : CH4(g) + 2O2(g) <=> CO2(g) + 2H2O(l) H r = -170.8 kJ mol -1 Which of the following statements is not true:- At equilibrium, the concentrations of CO2(g) and H2O(l) are not equal The equilibrium constant for the reaction is given by K p = [ CO2 ] [ CH4 ][ O2 ] Addition of CH4(g) or O2(g) at equilibrium will cause a shift to the right The reaction is exothermic The relation between the equilibrium constant K and standard Gibbs free energy change G is: G = -RT K G = RT K G = -2.303 RT K Both A and C are correct The standard equilibrium constant, Kp at 298 K for the reaction, N2(g) + 3H2(g) <=> 2NH3(g) is 5.8 10 5 . The value of standard equilibrium constant, if the concentration of gases is expressed in terms of mol/L, will be : [Given : R = 0.08314 L bar K -1 mol -1 ] 3.99 10 9 3.51 10 6 3.84 10 7 3.56 10 8 3 O2 (g) 2 O3 (g) for the above reaction at 298 K, K c is found to be 3.0 10 -59 . If the concentration of O2 at equilibrium is 0.040 M then concentration of O3 in M is 1.9 10 -63 2.4 10 31 1.2 10 21 4.38 10 -32 Consider the following reaction in a sealed vessel at equilibrium with concentrations of N 2 = 3.0 10 -3 M , O 2 = 4.2 10 -3 M and NO = 2.8 10 -3 M . 2NO(g) <=> N2(g) + O2(g) If 0.1 mol L -1 of NO(g) is taken in a closed vessel, what will be degree of dissociation ( ) of NO(g) at equilibrium? 0.00889 0.0889 0.8889 0.717 For the reaction A(g) <=> 2B(g) , the backward reaction rate constant is higher than the forward reaction rate constant by a factor of 2500, at 1000 K. [Given : R = 0.0831 L atm mol -1 K -1 ] Kp for the reaction at 1000 K is 0.021 83.1 2.077 10 5 0.033 For the reaction PCl 5(g) PCl 3(g) + Cl 2(g) , the degree of dissociation is at equilibrium pressure P . The equilibrium constant K p is: 2 P 1 - 2 2 P 2 1 - 2 P 1 - 2 1 - 2 The reaction 2A(g) + B(g) 3C(g) + D(g) is begun with concentrations of A and B both at 1.00 M . When equilibrium is reached, [D] = 0.25 M . The value of K c is: 0.82 0.15 1.25 0.45 At a given temperature, the equilibrium constant for N 2O 4(g) ightleftharpoons 2NO 2(g) is K p . If the total pressure at equilibrium is P and the degree of dissociation is α , then K p is: 4α 2P 1-α 2 4α 2P 1-α α 2P 1-α 2α 2P 1-α 2 A plot of K vs 1/T for a reaction is a straight line with a positive slope. This indicates that the reaction is: Exothermic Endothermic Athermal Spontaneous at all temperatures Consider the equilibrium: CaCO 3(s) CaO(s) + CO 2(g) . If the volume of the container is halved at constant temperature, what happens to the equilibrium pressure of CO 2 ? Remains constant Becomes double Becomes half Increases four times A vessel at 1000 K contains CO 2 with a pressure of 0.5 atm. Some of the CO 2 is converted into CO on the addition of graphite. If the total pressure at equilibrium is 0.8 atm, the value of K p is: 1.8 atm 3 atm 0.3 atm 0.18 atm The reaction quotient Q c for the reaction A + B C + D is 100, while the equilibrium constant K c is 10. The reaction will: Proceed in the backward direction Proceed in the forward direction Be at equilibrium Stop completely For the decomposition of N 2O 4(g) to 2NO 2(g) , the degree of dissociation is and the initial pressure is P . The equilibrium constant K p in terms of and total pressure P t is: 4 2 P t 1- 2 4 P t 1- 2 P t 1- 2 4 2 P t 1- The relationship between the degree of dissociation and vapour density D (initial) and d (equilibrium) is given by: = D-d d(n-1) = d-D D(n-1) = D-d D(n-1) = d-D d(n-1) For the solid dissociation NH 2 COONH 4 (s) 2NH 3 (g) + CO 2 (g) , if the total pressure at equilibrium is P , then K p is: 4P 3 / 27 P 3 / 27 4P 2 / 9 P 2 / 3 The vapour density of N 2O 4 at a certain temperature is 30 . What is the percentage dissociation of N 2O 4 at this temperature? (Molecular weight of N 2O 4 = 92 ) 53.3 % 25.7 % 46.7 % 60.0 % For the reaction CO(g) + H 2O(g) CO 2(g) + H 2(g) , the equilibrium constant K is 5 . If 1 mole of each reactant is taken in a 1 L vessel, what is the equilibrium concentration of CO 2 ? 0.69 M 0.50 M 1.00 M 0.85 M A plot of K vs 1/T for an exothermic reaction is a straight line with: A positive slope A negative slope Zero slope An exponential curve The following equilibrium constants are given: N2 + 3H2 <=> 2NH3 ; K 1 N2 + O2 <=> 2NO ; K 2 H2 + 1/2 O2 <=> H2O ; K 2 The equilibrium constant for the oxidation of NH3 by oxygen to give NO is K 2 ,K 3 2 K 1 K 1 ,K 2 K 3 K 2 2 ,K 3 K 1 K 2 ,K 3 3 K 1