Free NEET Chemistry multiple-choice questions on Rate Law & Order. Attempt each question and reveal the answer with a full explanation.
For an elementary reaction M N , the rate of disappearance of M increases by a factor of 8 when the concentration of M is doubled. The order of the reaction with respect to M is: 3 2 1 0 For a reaction X Y , the rate of reaction becomes 27 times when the concentration of X is tripled. The order of the reaction is: 3 2 1 0 For a reaction A + B products , doubling the concentration of A the rate becomes 4 times and doubling the concentration of B has no effect on the rate. The rate equation is: Rate = k[A] 2[B] 0 Rate = k[A] 1[B] 0 Rate = k[A] 2[B] 1 Rate = k[A] 1[B] 1 Which of the following represents the unit of the rate constant for a reaction of the n th order? (mol L -1 ) 1-n s -1 (mol L -1 ) n-1 s -1 (mol L -1 ) n s -1 (mol L -1 ) 1-n s The rate constant of a first-order reaction is 4 10 -3 s -1 . At what concentration of the reactant will the rate be 2 10 -4 mol L -1 s -1 ? 0.05 M 0.5 M 0.02 M 0.2 M Which of the following statements about the 'order of reaction' is true? It can be a fraction It must be a whole number It is always equal to the molecularity It can be determined from the balanced chemical equation For a reaction A B , the rate of reaction is found to triple when the concentration of A is tripled. The order of the reaction is: 1 0 2 3 What is the unit of the rate constant for a reaction with an overall order of 0.5 ? mol 0.5 L -0.5 s -1 mol -0.5 L 0.5 s -1 mol L -1 s -1 s -1 For an elementary reaction M + N P , the molecularity and order are respectively: 2, 2 1, 1 2, 1 1, 2 The reaction A + 2B C is first-order with respect to A and zero-order with respect to B . The concentration of B is doubled. The new rate will be: The same as the original rate Double the original rate Four times the original rate Half of the original rate The rate of a reaction A + B C is given by R = k[A] x[B] y . If the concentration of A is doubled, the rate becomes 4 times. If the concentration of B is doubled, the rate is doubled. What is the overall order of the reaction? 3 2 1 4 For a reaction A + 2B C , the rate is R = k[A][B] 0 . If the concentration of B is tripled, the rate of reaction will: Remain unchanged Increase by 3 times Increase by 9 times Decrease by 3 times The reaction X Y is second-order with respect to X . If the concentration of X is increased by a factor of 3, the rate of formation of Y will: Increase by 9 times Increase by 3 times Increase by 6 times Increase by 27 times What is the order of the reaction whose rate constant has the same units as the rate of reaction? Zero First Second Third Which statement is incorrect regarding the molecularity of a reaction? Molecularity can be zero or a fraction It is the number of reacting species taking part in an elementary reaction It is always a whole number It cannot be determined for a complex reaction The reaction A + B C has zero order with respect to A and first order with respect to B . The plot of rate vs [A] will be: A straight line parallel to the [A] axis A straight line passing through the origin A rectangular hyperbola An exponential curve The unit of rate constant for a third-order reaction is: L 2 mol -2 s -1 L mol -1 s -1 mol L -1 s -1 s -1 For the reaction 2HI → H 2 + I 2 , the rate law is Rate = k[HI] 2 . This reaction is: Bimolecular and second order Unimolecular and first order Bimolecular and first order Unimolecular and second order If the rate of a reaction is expressed as Rate = k[A] x [B] y , and the reaction is found to be zero-order with respect to A and second-order with respect to B , what happens to the rate if the concentration of A is tripled and B is halved? Decreases to 1/4 of the original rate Increases to 3/4 of the original rate Remains the same Decreases to 1/2 of the original rate A chemical reaction X Y follows second-order kinetics. If the concentration of X is increased to three times, the rate of formation of Y will become: 9 times 3 times 27 times 1/9 times The rate of a reaction is given by Rate = k[A] 2[B] . What are the units of k if the concentration is in mol L -1 and time is in s ? L 2 mol -2 s -1 L mol -1 s -1 mol L -1 s -1 s -1 For a reaction A B , the rate law is Rate = k[A] n . If the initial concentration of A is quadrupled and the rate doubles, the value of n is: 0.5 1 2 0 The unit of rate constant for a reaction is L mol -1 s -1 . This suggests the reaction is of: Second order First order Zero order Third order If the rate constant for a reaction is k = 3.4 10 -4 mol -2 L 2 s -1 , the overall order of the reaction is: 3 2 1.5 0 The rate of reaction between two reactants A and B decreases by a factor of 4 if the concentration of reactant B is doubled. The order of this reaction with respect to reactant B is :- 2 -1 1 -2 The given graph is a representation of kinetics of a reaction. The y and x axes for zero and first order reactions, respectively are zero order (y = concentration and x = time), first order (y = rate constant and x = concentration) zero order (y = rate and x = concentration), first order (y = t 1/2 and x = concentration) zero order (y = rate and x = concentration), first order (y = rate and x = t 1/2 ) zero order (y = concentration and x = time), first order (y = t 1/2 and x = concentration) For a certain reaction, the rate = k[A] 2[B] , when the initial concentration of A is tripled keeping concentration of B constant, the initial rate would Decrease by a factor of nine Increase by a factor of six Increase by a factor of nine Increase by a factor of three Match List I with List II : array llll ; & List-I; (Order of reaction) & ; & List-II; (Unit of rate constant) A. & Zero order & I. & mol -1 L s -1 B. & First order & II. & mol -2 L 2 s -1 C. & Second order & III. & s -1 D. & Third order & IV. & mol L -1 s -1 array Choose the correct answer from the options given below : A-IV, B-III, C-II, D-I A-IV, B-III, C-I, D-II A-I, B-II, C-III, D-IV A-IV, B-II, C-I, D-III For a reaction A B , the rate of reaction doubles when the concentration of A is increased by four times. The order of reaction is: 1/2 1 2 Zero For a reaction A + B C , the rate law is Rate = k[A] 2 [B] . If the volume of the reaction vessel is doubled, the rate of reaction will: Decrease to 1/8 times Increase to 8 times Decrease to 1/4 times Remain unchanged During the decomposition of H 2O 2 in the presence of I - , the steps are: (1) H 2O 2 + I - H 2O + IO - (slow), (2) H 2O 2 + IO - H 2O + I - + O 2 (fast). The order of reaction with respect to H 2O 2 is: 1 2 Zero 0.5 If the rate constant for a reaction is k = 2.5 10 -4 mol -1/2 L 1/2 s -1 , the order of the reaction is: 1.5 0.5 2.5 -0.5 In the reaction A + B Products , if concentration of A is kept constant and B is doubled, the rate doubles. If concentration of B is kept constant and A is doubled, the rate quadruples. The rate law is: Rate = k[A] 2[B] Rate = k[A][B] 2 Rate = k[A][B] Rate = k[A] 2[B] 2 A plot of the rate of reaction versus the square of the concentration of a reactant [A] 2 gives a straight line passing through the origin. The order of the reaction is: Second order First order Zero order Half order 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 A and B are doubled. The rate law for the reaction can be written as: Rate = k[A] 2[B] Rate = k[A][B] 2 Rate = k[A][B] Rate = k[A] 2[B] 2 For a reaction 2A B + C , it is found that the rate increases 4 times when the concentration of A is doubled. What is the unit of the rate constant for this reaction? L mol -1 s -1 s -1 mol L -1 s -1 L 2 mol -2 s -1 The half-life of a reaction is found to be inversely proportional to the cube of the initial concentration. The order of the reaction is: 4 3 2 5 A reaction follows the rate law Rate = k[A] 2[B] 1/2 . What happens to the rate if the concentration of A is halved and the concentration of B is increased four times? Remains unchanged Doubles Halves Increases 4 times For a reaction A + B C , the following data were obtained: (i) [A]=0.1, [B]=0.1, Rate=R; (ii) [A]=0.2, [B]=0.1, Rate=4R; (iii) [A]=0.1, [B]=0.2, Rate=2R. The rate law is: Rate = k[A] 2[B] Rate = k[A][B] 2 Rate = k[A] 2[B] 2 Rate = k[A][B] For a reaction A B , the rate expression is Rate = k[A] n . If the rate of reaction increases 100 times when the pH is decreased from 3 to 2 , what is the order n with respect to H + ions (assuming A is H + )? 2 1 0 10 For a reaction A B , it is found that the rate of reaction quadruples when the concentration of A is doubled. The unit of the rate constant is: L mol -1 s -1 mol L -1 s -1 s -1 L 2 mol -2 s -1 For the reaction A + B Products, doubling the concentration of A increases the rate by 2 times and doubling the concentration of B increases the rate by 8 times. The overall order of the reaction is: 4 3 5 2 If the rate constant of a reaction is k = 4.5 10 -4 L 2 mol -2 s -1 , what is the order of the reaction? Third order Second order First order Zero order The reaction 2A + B A 2B is an elementary reaction. If the volume of the container is reduced to one-third, the rate of reaction will: Increase by 27 times Increase by 9 times Decrease by 27 times Decrease by 9 times For a reaction, Rate = k[A] 3/2 [B] -1 . The overall order of the reaction is: 1/2 3/2 5/2 -1 For the reaction A + B Products , it is observed that double the concentration of A only, the rate doubles; and double the concentration of both A and B , the rate becomes 8 times. The rate law is: Rate = k[A][B] 2 Rate = k[A] 2[B] Rate = k[A][B] Rate = k[A] 2[B] 2 The decomposition of NH 3 on a platinum surface is a zero-order reaction. What is the rate of production of N 2 and H 2 if k = 2.5 10 -4 mol L -1 s -1 ? (Reaction: 2NH 3 N 2 + 3H 2 ) Rate( N 2 ) = 2.5 10 -4 , Rate( H 2 ) = 7.5 10 -4 Rate( N 2 ) = 1.25 10 -4 , Rate( H 2 ) = 3.75 10 -4 Rate( N 2 ) = 2.5 10 -4 , Rate( H 2 ) = 2.5 10 -4 Rate( N 2 ) = 5.0 10 -4 , Rate( H 2 ) = 7.5 10 -4 If the concentration is expressed in mol/L and time in s , the unit of rate constant for a 1.5 order reaction is: mol -0.5 L 0.5 s -1 mol 0.5 L -0.5 s -1 mol L -1 s -1 mol -1 L s -1 In a reaction, A + B → Product , rate is doubled when the concentration of B is doubled, and rate increases by a factor of 8 when the concentration of both A and B are doubled. The rate law for the reaction can be written as: Rate = k[A] 2[B] Rate = k[A][B] 2 Rate = k[A][B] Rate = k[A] 2[B] 2 For a reaction X → Y , the rate constant is k . If the concentration of X is doubled, the half-life of the reaction is halved. The order of the reaction is: Second order Zero order First order Half order If the rate constant for a reaction is k = 3.2 10 -4 mol -0.5 L 0.5 s -1 , the order of the reaction is: 1.5 0.5 2.5 1.0 For a reaction A B , the rate constant is k . If the plot of 1 [A] versus time t is a straight line with a positive slope, the order of the reaction is: 2 1 0 3 For an elementary reaction 2A + B C , if the volume of the vessel is reduced to one-half of its original volume, the rate of the reaction will: Increase by 8 times Increase by 4 times Decrease by 8 times Increase by 2 times For a reaction A + B C , the experimental rate law is Rate = k[A] 1/2 [B] 2 . If the concentration of both A and B are doubled, the rate of reaction increases by a factor of: 4 2 8 4 2 For a reaction A + B C , the rate law is Rate = k[A] x [B] y . If the concentration of A is kept constant and B is doubled, the rate increases by 4 times. If both A and B are doubled, the rate increases by 8 times. The values of x and y are: x=1, y=2 x=2, y=1 x=1, y=1 x=2, y=2 The rate of a reaction increases 4-fold when the concentration of reactant A is doubled. The order of the reaction with respect to A is: 2 1 0 0.5 In a pseudo-first-order reaction A + B Product , where B is in large excess, the rate constant k' observed is 2.0 10 -3 s -1 . If the actual rate law is Rate = k[A][B] and [B] = 0.5 M , what is the value of the true rate constant k ? 4.0 10 -3 L mol -1 s -1 1.0 10 -3 L mol -1 s -1 2.0 10 -3 L mol -1 s -1 0.5 10 -3 L mol -1 s -1 If the concentration of reactant is increased by factor of x and the rate increases by factor of y , the order of reaction n is: n = y x n = x y n = y/x n = log (y/x) For a reaction A B , the rate doubles when the concentration of A is increased 8 times. The order of the reaction is: 1/3 3 1/2 2 If the rate constant k of a reaction has the units L 1.5 mol -1.5 s -1 , what is the overall order of the reaction? 2.5 1.5 0.5 -0.5 In the reaction A + 2B Products , the rate law is Rate = k[A][B] . If B is taken in large excess, the reaction becomes: Pseudo-first order with respect to A Second order Pseudo-zero order with respect to B First order with respect to B Which of the following units represents a reaction of order 1.5 ? mol -0.5 L 0.5 s -1 mol 0.5 L -0.5 s -1 mol -1.5 L 1.5 s -1 mol 1.5 L -1.5 s -1 A reaction is first order in A and second order in B . How does the rate change if the concentration of A is doubled and B is halved? Rate is halved Rate is doubled Rate remains the same Rate increases by 4 times The hydrolysis of an ester in the presence of an alkali follows which order? Second order First order Zero order Pseudo-first order What is the unit of the rate constant ( k ) for a reaction with an overall order of 2.5 if concentration is in mol L -1 and time in s ? L 1.5 mol -1.5 s -1 mol 1.5 L -1.5 s -1 L 2.5 mol -2.5 s -1 mol L -1 s -1 For a reaction A + B C , the rate is R = k[A][B] 2 . If the volume of the reaction vessel is reduced to 1/3 of its original volume, the rate of reaction will: Increase by 27 times Increase by 9 times Decrease by 9 times Increase by 3 times A reaction A B follows second-order kinetics. If the concentration of A is increased by 3 times, the rate of formation of B will increase by: 9 times 3 times 6 times 27 times The rate constant for a reaction is k = 3 10 -5 atm -1 s -1 . The order of the reaction is: Second order First order Zero order Third order The reaction of hydrogen and iodine monochloride is given as: H2(g) + 2ICl(g) -> 2HCl(g) + I2(g) The reaction is of first order with respect to H2(g) and ICl(g) , following mechanisms were proposed. Mechanism A: H2(g) + 2ICl(g) -> 2HCl(g) + I2(g) Mechanism B: H2(g) + ICl(g) -> HI(g) + HCl(g) ; slow HI(g) + ICl(g) -> HCl(g) + I2(g) ; fast Which of the above mechanism(s) can be consistent with the given information about the reaction? A and B both neither A nor B A only B only For the reaction A+B products , it is observed that : (1) On doubling the initial concentration of A only, the rate of reaction is also doubled and (2) On doubling the initial concentration of both A and B, there is a change by a factor of 8 in the rate of the reaction. The rate of this reaction is given by : rate =k[A][B] rate =k[A] 2[B] rate =k[A][B] 2 rate =k[A] 2[B] 2 Consider the reaction between chlorine and nitric oxide Cl2(g) + 2NO(g) -> 2NOCl(g) On doubling the concentration of both reactants, the rate of the reaction increases by a factor of 8. However, if only the concentration of Cl2 is doubled, the rate increases by a factor of 2. The order of this reaction with respect to NO is : 3 0 1 2 The mechanism of a hypothetical reaction X 2 + Y 2 2XY is given below: (i) X 2 X + X (fast), (ii) X + Y 2 XY + Y (slow), (iii) X + Y XY (fast). The overall order of the reaction will be: 1.5 2 1 Zero Consider the reaction: Cl 2(g) + 2NO(g) 2NOCl(g) . The mechanism is: (1) NO + Cl 2 NOCl 2 (fast equilibrium), (2) NOCl 2 + NO 2NOCl (slow). The rate law is: Rate = k[NO] 2[Cl 2] Rate = k[NO][Cl 2] Rate = k[NO][Cl 2] 2 Rate = k[NOCl 2][NO] The mechanism of the reaction 2NO + O 2 2NO 2 is suggested as follows: NO + NO N 2O 2 (fast), N 2O 2 + O 2 2NO 2 (slow). The rate law for the reaction is: Rate = k[NO] 2[O 2] Rate = k[N 2O 2][O 2] Rate = k[NO][O 2] Rate = k[NO] 2 A reaction follows the mechanism: (1) A + B C (fast), (2) C + D E (slow). The rate law for the overall reaction A + B + D E is: Rate = k[A][B][D] Rate = k[C][D] Rate = k[A][B] Rate = k[D] In the reaction 2A + B → C + D , the following data were obtained: (1) [A]=0.1, [B]=0.1, Rate=0.01 ; (2) [A]=0.2, [B]=0.1, Rate=0.02 ; (3) [A]=0.1, [B]=0.2, Rate=0.04 . The rate law is: Rate = k[A][B] 2 Rate = k[A] 2[B] Rate = k[A][B] Rate = k[A] 2[B] 2 For the reaction 2O 3(g) 3O 2(g) , the following mechanism is proposed: (i) O 3 O 2 + O (fast equilibrium), (ii) O + O 3 2O 2 (slow). The rate law for the reaction is: Rate = k [O 3] 2 [O 2] -1 Rate = k [O 3] 2 Rate = k [O 3] [O 2] Rate = k [O 3] 2 [O 2] The order of a reaction which has a rate expression Rate = k[A] 1[B] 1/2 [C] 3/2 is: 3 2 1.5 1 The half-life period of a substance is 50 minutes at a certain concentration. When the concentration is reduced to one-half of the initial concentration, the half-life period becomes 100 minutes. The order of the reaction is: 2 1 0 0.5 For a reaction A Products , the plot of the square root of the rate versus concentration [A] is a straight line passing through the origin. The order of the reaction is: 2 1 0.5 0 For a reaction A + B C , doubling the concentration of A triples the rate, and doubling the concentration of B quadruples the rate. The overall order of the reaction is: log 2 3 + 2 3 5 log 3 2 + 2 For a reaction 2A + B Products , the following mechanism is proposed: A + A A 2 (fast), A 2 + B Product (slow). The rate law is: Rate = k[A] 2[B] Rate = k[A][B] Rate = k[A 2][B] Rate = k[A] 2 The unit of rate constant for a reaction of order n = -1 is: mol 2 L -2 s -1 L mol -1 s -1 s -1 mol L -1 s -1 The reaction H 2 + Br 2 2HBr has a complex rate law: Rate = k[H 2][Br 2] 1/2 1 + k'[HBr]/[Br 2] . What is the order of the reaction at the very beginning when [HBr] 0 ? 1.5 2 1 0.5 Which of the following statements is FALSE regarding the molecularity of a reaction? It can be zero or fractional It is always a whole number It is determined from the mechanism It cannot be more than three usually