Free NEET Chemistry multiple-choice questions on Arrhenius Equation. Attempt each question and reveal the answer with a full explanation.
According to the collision theory, the rate of reaction is given by Rate = P Z AB e -E a/RT . What does P represent? Steric factor Collision frequency Activation energy Fraction of molecules with sufficient energy Threshold energy is equal to: Activation energy + Average kinetic energy of molecules Activation energy - Average kinetic energy of molecules Activation energy Average kinetic energy of molecules The activation energy of a chemical reaction can be determined from the slope of the plot of: ln k vs 1/T ln k vs T log k vs T 1 k vs T Which of the following does NOT affect the rate constant of a reaction? Concentration of reactants Temperature Presence of a catalyst Nature of reactants The temperature coefficient of most reactions lies between: 2 and 3 1 and 2 3 and 4 0 and 1 A catalyst increases the rate of reaction by: Providing an alternative pathway with lower activation energy Increasing the average kinetic energy of molecules Increasing the number of collisions Decreasing the enthalpy of the reaction The specific rate constant of a first-order reaction depends on: Temperature Concentration of the reactant Time of the reaction Concentration of the product The pre-exponential factor ( A ) in the Arrhenius equation has the same units as: The rate constant ( k ) The activation energy ( E a ) The rate of reaction The temperature ( T ) According to collision theory, not all collisions result in a chemical reaction. The collisions that lead to product formation are called 'effective collisions'. These require: Threshold energy and proper orientation Only threshold energy Only proper orientation Low activation energy and high pressure A catalyst increases the rate of a chemical reaction by: Lowering the activation energy Increasing the average kinetic energy of molecules Increasing the number of collisions Decreasing the enthalpy of the reaction Which of the following expressions is correct for the temperature coefficient ( )? = k T+10 / k T = k T+10 - k T = k T / k T+10 = (k T+10 / k T) The rate of a chemical reaction is doubled for every 10 o C rise in temperature. If the temperature is raised by 50 o C , the rate of the reaction increases by: 32 times 10 times 64 times 50 times In the Arrhenius equation k = A e -E a/RT , as T , the rate constant k becomes equal to: A 0 1 Which statement regarding collision theory is incorrect? Every collision between reactant molecules results in a chemical reaction. Reactant molecules must possess a minimum amount of kinetic energy. Reactant molecules must collide with proper orientation. The rate of reaction is proportional to the collision frequency. Threshold energy is defined as: The sum of activation energy and average kinetic energy of reactants. The energy difference between reactants and products. The minimum energy required to break a chemical bond. The energy of the transition state alone. Which of the following statements is correct for a catalyst? It decreases the activation energy. It increases the activation energy. It increases the average kinetic energy of molecules. It changes the enthalpy of the reaction. The plot of k vs 1/T is a straight line. What is the slope of this line? -E a / R E a / R -E a / 2.303R A Which of the following describes the effect of temperature on the rate constant k ? Rate constant increases exponentially with temperature. Rate constant increases linearly with temperature. Rate constant decreases with increasing temperature. Rate constant is independent of temperature. The temperature coefficient of a reaction is 2 . If the temperature is increased from 20 C to 50 C , the rate of reaction will increase by a factor of: 8 6 3 30 According to the Arrhenius equation, the slope of the plot of log k versus 1/T is: -E a / 2.303R -E a / R E a / R 2.303 R / E a The activation energy for a simple chemical reaction A → B is E a in the forward direction. The activation energy for the reverse reaction: Can be less than, more than, or equal to E a Is always equal to E a Is always less than E a Is always negative Which of the following statements is correct regarding the effect of temperature on the rate of reaction? Rate constant increases exponentially with increase in temperature Rate of reaction increases linearly with increase in temperature Activation energy decreases with increase in temperature Number of collisions decreases with increase in temperature In collision theory, the fraction of effective collisions ( f ) is related to activation energy by: f = e -E a/RT f = A e -E a/RT f = E a/RT f = log (E a/RT) The activation energy of a reaction is zero. The rate constant of this reaction at 280 K is 1.6 10 6 s -1 . The rate constant at 300 K is: 1.6 10 6 s -1 3.2 10 6 s -1 1.6 10 7 s -1 0 The temperature coefficient of a reaction is 2 . How many times does the rate of reaction increase when the temperature is raised from 300 K to 350 K ? 32 5 10 64 According to collision theory, the rate of reaction is given by Rate = Z AB ∙ e -E a/RT . The factor P (steric factor) is introduced to account for: The orientation requirement of colliding molecules The change in enthalpy during collision The increase in collision frequency with temperature The threshold energy of the reactants A catalyst increases the rate of reaction by providing an alternative pathway with a: Lower activation energy Higher activation energy Higher threshold energy Lower enthalpy of reaction In collision theory of chemical reactions, Z AB represents: The collision frequency of reactants A and B The fraction of molecules with energy greater than E a The probability factor The steric factor Which of the following expressions represents the fraction of effective collisions ( f ) according to Arrhenius equation? f = e -E a/RT f = A e -E a/RT f = (E a/RT) f = e E a/RT Which of the following expressions correctly represents the temperature dependence of the rate constant? k 2 k 1 = E a R [ T 2 - T 1 T 1 T 2 ] k 2 k 1 = E a R [ T 1 - T 2 T 1 T 2 ] k 1 k 2 = E a R [ T 2 - T 1 T 1 T 2 ] k 2 k 1 = R E a [ T 2 - T 1 T 1 T 2 ] A reaction having equal energies of activation for forward and reverse reactions has S = 0 G = 0 H = 0 H = G = S = 0 The addition of a catalyst during a chemical reaction alters which of the following quantities ? Entropy Internal energy Enthalpy Activation energy The slope of Arrhenius plot ( k v/s 1 T ) of first order reaction is -5 10 3 K . The value of E a of the reaction is. Choose the correct option for your answer. [Given R = 8.314 JK -1 mol -1 ] 83.0 kJ mol -1 166 kJ mol -1 -83 kJ mol -1 41.5 kJ mol -1 The fraction of molecules having energy equal to or greater than the activation energy is given by: e -E a/RT ln (E a/RT) A e -E a/RT E a RT Given below are two statements : one is labelled as Assertion A and the other is labelled as Reasons R : Assertion A : A reaction can have zero activation energy. Reasons R : The minimum extra amount of energy absorbed by reactant molecules so that their energy becomes equal to threshold value, is called activation energy. In the light of the above statements, choose the correct answer from the options given below : Both A and R are true and R is the correct explanation of A Both A and R are true and R is NOT the correct explanation of A A is true but R is false A is false but R is true Activation energy of any chemical reaction can be calculated if one knows the value of rate constant at standard temperature probability of collision orientation of reactant molecules during collision rate constant at two different temperatures Given below is an expression for the rate constant of a first-order reaction occurring at a certain temperature, T (K). k = 14.34 - 1.25 10 4 T The energy of activation in kcal mol -1 for the reaction is : (Given: k in s -1 , R = 1.987 cal mol -1 K -1 ) 12.42 18.63 14.34 24.84 The activation energy of a reaction can be determined from the slope of which of the following graphs? ln k vs 1/T ln k vs T k vs T log k vs T In a zero-order reaction, for every 10 o C rise in temperature, the rate is doubled. If the temperature is increased from 10 o C to 100 o C , the rate of the reaction will become: 512 times 256 times 1024 times 90 times For a reaction, the activation energy is zero. The rate constant ( k ) for this reaction will be: Independent of temperature Increasing with temperature Decreasing with temperature Proportional to T A reaction having equal activation energies for forward and reverse reactions has: H = 0 G = 0 S = 0 H = G = S = 0 For an endothermic reaction, energy of activation is E a and enthalpy of reaction is Δ H . The minimum value of E a will be: More than Δ H Less than Δ H Equal to Δ H Zero In collision theory, the rate of reaction is proportional to e -E a/RT which represents: The fraction of molecules with energy equal to or greater than E a The total number of collisions The fraction of molecules with energy less than E a The orientation factor According to the Arrhenius equation, a straight line is to be obtained by plotting log 10 k versus 1/T . The intercept on the y-axis will be: log 10 A ln A -E a/2.303R -E a/R The value of the rate constant for a reaction is 1.6 10 -3 s -1 at 300 K and 3.2 10 -3 s -1 at 310 K . The temperature coefficient of the reaction is: 2.0 1.5 3.0 2.5 Which of the following factors does NOT affect the frequency of collisions ( Z )? Activation energy Temperature Pressure Concentration What happens to the peak of the Maxwell-Boltzmann distribution curve when the temperature of the reaction mixture is increased? It shifts to the right and moves downward It shifts to the left and moves upward It shifts to the right and moves upward It remains at the same position For an exothermic reaction A B , the activation energy for the forward reaction is 40 kJ mol -1 and the enthalpy change ( H ) is -20 kJ mol -1 . The activation energy for the backward reaction B A is: 60 kJ mol -1 20 kJ mol -1 40 kJ mol -1 80 kJ mol -1 The term e -E a/RT in the Arrhenius equation represents: The fraction of molecules having energy equal to or greater than the activation energy The number of collisions per unit volume per second The total number of molecules in the system The probability of collisions with proper orientation The activation energy of a reaction is zero. If the rate constant at 300 K is 1.6 10 6 s -1 , then the rate constant at 310 K will be: 1.6 10 6 s -1 3.2 10 6 s -1 1.6 10 7 s -1 0 In an exothermic reaction X Y , the activation energy for the forward reaction is 30 kJ/mol . If the enthalpy of reaction ( ΔH ) is -20 kJ/mol , the activation energy for the reverse reaction is: 50 kJ/mol 10 kJ/mol 30 kJ/mol 20 kJ/mol For a reaction A + B ightarrow C + D , if the activation energy for the forward reaction is 150 kJ/mol and that for the backward reaction is 260 kJ/mol , what is the enthalpy change ( Δ H ) for the reaction? -110 kJ/mol 110 kJ/mol 410 kJ/mol -410 kJ/mol The slope of the Arrhenius plot ( ጒn k vs 1/T ) is -5 10 3 K . The value of activation energy is: ( R = 8.314 J ∙ K -1 mol -1 ) 41.57 kJ/mol 83.14 kJ/mol 1.66 kJ/mol 20.78 kJ/mol Which of the following energy level diagrams represents an endothermic reaction with the highest activation energy for the forward reaction? Diagram where products are at higher energy than reactants and the peak is far above both Diagram where reactants are at higher energy than products Diagram where products and reactants are at the same energy level Diagram where the peak is below the reactant energy level According to the collision theory of chemical reactions, the rate of reaction increases with temperature because: The fraction of molecules with energy greater than E a increases The activation energy decreases The threshold energy decreases The collision frequency decreases Which property of the reaction coordinate diagram is changed by the presence of a catalyst? The height of the activation energy barrier The energy of the reactants The energy of the products The enthalpy of the reaction The temperature coefficient of a reaction is 2.5 . How many times does the rate increase if the temperature is raised from 20 C to 50 C ? 15.625 7.5 12.5 25 The unit of the pre-exponential factor ( A ) in the Arrhenius equation for a second-order reaction is: L mol -1 s -1 s -1 mol L -1 s -1 L 2 mol -2 s -1 The rate of a certain reaction becomes double when the temperature is increased from 27 C to 37 C . The activation energy of the reaction is approximately: ( R = 8.314 J/K/mol ) 53.6 kJ/mol 100 kJ/mol 25 kJ/mol 10.5 kJ/mol Which of the following energy distributions is correct for molecules according to Maxwell-Boltzmann distribution? The most probable kinetic energy increases with temperature The fraction of molecules with high kinetic energy decreases with temperature The total area under the curve decreases as temperature increases The peak of the curve shifts to the left as temperature increases In the Maxwell-Boltzmann distribution of molecular kinetic energies, as the temperature increases, the fraction of molecules with the most probable kinetic energy: Decreases Increases Remains the same First increases then decreases Which of the following is NOT a characteristic of a catalyst? It increases the average kinetic energy of the reactants It provides an alternate pathway for the reaction It lowers the activation energy It does not change the equilibrium constant The activation energy for a reaction is E a and the rate constant at temperature T is k . If T , what happens to the value of k ? k approaches A k approaches 0 k approaches k approaches 1 For a reaction, the activation energy is E a = 0 . If the rate constant is k 1 at 300 K and k 2 at 350 K , then: k 1 = k 2 k 2 > k 1 k 1 > k 2 Relationship depends on the concentration If the activation energy for the forward reaction X ightarrow Y is E a and the enthalpy change ΔH is positive, which of the following is true for the backward reaction Y ightarrow X ? E a, back < E a E a, back > E a E a, back = E a ΔH = E a What is the effect of an increase in temperature on the 'Threshold Energy' of a reaction? It remains unchanged It increases It decreases It first increases then decreases A reaction has an activation energy of zero. What is the value of its rate constant at 400 K if the frequency factor A = 2.0 10 8 s -1 ? 2.0 10 8 s -1 0 1.0 10 8 s -1 Infinite Which of the following statements is correct regarding the frequency factor ( A ) in the Arrhenius equation k = A e -E a/RT ? It represents the frequency of binary collisions per unit volume. It is always independent of temperature. It has units of energy mol -1 . It decreases as the activation energy increases. For an endothermic reaction, the energy of activation for the forward reaction is E af and for the backward reaction is E ab . Which relationship is correct? E af > E ab E af < E ab E af = E ab E af + E ab = 0 According to the Arrhenius equation, a plot of k vs 1/T results in a straight line. What does the intercept on the Y-axis represent? A E a/R -E a/R A What is the relationship between threshold energy ( E th ), activation energy ( E a ), and the average kinetic energy of reactants ( E r )? E th = E a + E r E a = E th + E r E r = E th + E a E th = E a - E r What is the activation energy for a reaction if its rate doubles when the temperature is raised from 20 C to 35 C ? ( R = 8.314 J mol -1 K -1 ) 342 kJ mol -1 269 kJ mol -1 34.7 kJ mol -1 15.1 kJ mol -1 For a reaction A B , enthalpy of reaction is -4.2 kJ mol -1 and enthalpy of activation is 9.6 kJ mol -1 . The correct potential energy profile for the reaction is shown in option. Which plot of k vs 1 T is consistent with Arrhenius equation? The rate of a reaction quadruples when temperature changes from 27 C to 57 C . Calculate the energy of activation. Given R = 8.314 J K -1 mol -1 , 4 = 0.6021 38.04 kJ/mol 380.4 kJ/mol 3.80 kJ/mol 3804 kJ/mol When the temperature of a reaction is increased from 27 o C to 37 o C , the rate of reaction doubles. What is the activation energy ( E a ) in kJ/mol ? ( R = 8.314 J/K/mol ) 53.6 100.2 25.1 10.5 The rate constant k of a reaction is measured at different temperatures T , and the data is plotted as k vs 1/T . The slope of the line is found to be -5.8 10 3 K . The activation energy of the reaction is: ( R = 8.314 J K -1 mol -1 ) 48.2 kJ mol -1 4.82 kJ mol -1 58.0 kJ mol -1 24.1 kJ mol -1 If the activation energy of a reaction is very low, the reaction is likely to be: Very fast Very slow Independent of temperature Reversible If the activation energy of a reaction is 83.14 kJ mol -1 , the ratio of rate constants at 600 K and 500 K ( k 600 /k 500 ) is approximately: ( R = 8.314 J K -1 mol -1 ) 10 1.45 10 0.34 10 2.0 10 0.72 The activation energy for a reaction is 100 kJ/mol . In the presence of a catalyst, the activation energy is lowered to 80 kJ/mol at 300 K . How many times does the rate of reaction increase? ( R = 8.314 J/K/mol ) e 8.02 20 e 2 e 20 The activation energy ( E a ) of a reaction is 50 kJ/mol . In the presence of a catalyst, E a decreases to 40 kJ/mol . By what factor does the rate increase at 300 K if the pre-exponential factor remains constant? e 4.01 e 10 10 1.74 2 The rate constant of a reaction is k = 2.1 10 -2 s -1 at 300 K and 4.2 10 -2 s -1 at 310 K . The activation energy of the reaction is: 53.6 kJ/mol 43.6 kJ/mol 33.6 kJ/mol 63.6 kJ/mol A first-order reaction is 50 % complete in 30 minutes at 27 o C and in 10 minutes at 47 o C . The activation energy of the reaction is: 43.85 kJ/mol 55.2 kJ/mol 22.1 kJ/mol 10.5 kJ/mol For a reaction, the rate constant k at 27 o C is 1.5 10 -5 s -1 and the collision frequency Z is 1.5 10 11 s -1 . The value of e -E a/RT is: 10 -16 10 16 1.5 10 -5 1.5 10 6 The Arrhenius equation is k = A e -E a/RT . What is the value of the rate constant k when the activation energy E a is very high and the temperature T is very low ( T → 0 )? 0 A ∞ 1 The activation energy of a reaction is 9.0 kcal/mol . The increase in the rate constant when the temperature is raised from 298 K to 308 K is approximately: 63% 100% 50% 10% In the presence of a catalyst, the activation energy of a reaction is lowered by 2 kcal/mol at 300 K . The rate of the reaction will increase by: 28 times 2 times 10 times 100 times The rate of a reaction at 300 K is R 1 . When the temperature is increased to 310 K , the rate increases to R 2 . If the activation energy is 53.6 kJ/mol , what is the ratio R 2/R 1 ? (Given R = 8.314 J K -1 mol -1 ) 2 3 1.5 4 Which of the following does NOT change when a positive catalyst is added to a reaction? Enthalpy of reaction ( H ) Activation energy ( E a ) Rate constant ( k ) Threshold energy The activation energy of a reaction is 50 kJ/mol . By what factor will the rate constant increase if the temperature is raised from 300 K to 310 K ? (Take R = 8.314 J/K/mol ) 1.88 2.55 1.22 3.10 The rate of a reaction increases by 2.303 times when the temperature is raised from 300 K to 310 K . What is the value of activation energy in cal/mol ? ( R = 2 cal/K/mol , ln 2.303 = 0.834 ) 15514 31028 7757 20000 For the parallel reaction A B ( k 1 ) and A C ( k 2 ), if the activation energies are E 1 and E 2 respectively, the overall activation energy E a for the disappearance of A is: k 1 E 1 + k 2 E 2 k 1 + k 2 E 1 + E 2 E 1 + E 2 2 k 2 E 1 + k 1 E 2 k 1 + k 2 In a Maxwell-Boltzmann distribution curve, if the temperature is increased, the most probable kinetic energy: Increases, and the fraction of molecules possessing it decreases Increases, and the fraction of molecules possessing it increases Decreases, and the fraction of molecules possessing it decreases Remains constant, but the curve broadens For an elementary chemical reaction, the Arrhenius plot is given below. If the energy of activation is 6.64 kJ mol -1 and R = 8.3 J K -1 mol -1 , the temperature at which the rate constant becomes e 2 min -1 , is 125 K 150 K 200 K 250 K