Chemistry - Chemical Kinetics - Quiz-9

The conversion of molecules X to Y follows second order kinetics. If concentration of X is increased to three times how will it affect the rate of formation of Y?

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6 times
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9 times
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12 times
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3 times

The rate of the chemical reaction doubles for an increase of 10 K in absolute temperature from 298 K. The activation energy of the chemical reaction is ?

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55.6 Jmol^-1
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45.6 kJmol^-1
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52.9 kJmol^-1
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45.7 Jmol^-1

The activation energy for the reaction 2HI(g) → H₂(g)+ I₂(g) is 209.5 kJ mol⁻¹ at 581K. What is the fraction of molecules of reactants having energy equal to or greater than activation energy?

$1 . 2.31 \times 10^{- 16} 2 . 3.52 \times 10^{- 18} 3 . 1.47 \times 10^{- 19} 4 . 2.13 \times 10^{- 20}$

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The rate constant for a first order reaction is 60 s^–1. How much time will it take to reduce the initial concentration of the reactant to its 1/16^th value?

$1 . 2.3 \times 10^{- 2} s 2 . 4.6 \times 10^{- 2} s 3 . 3.1 \times 10^{- 3} s 4 . 1.4 \times 10^{- 2} s$

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A first order reaction takes 40 min for 30% decomposition. The half life of the reaction will be:

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88.8 min
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3. 67.2 min
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2. 94.3 min
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77.7 min

The rate constant for the decomposition of hydrocarbons is 2.418 × 10^–5s^–1 at 546 K. If the energy of activation is 179.9 kJ/mol, the value of pre-exponential factor will be :

$1 . 4.0 \times 10^{12} s^{- 1} 2 . 7.8 \times 10^{- 13} s^{- 1} 3 . 3.8 \times 10^{- 12} s^{- 1} 4 . 4.7 \times 10^{12} s^{- 1}$

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For a reaction A → Product,

with k = 2.0 × 10^–2s^–1, if the initial concentration of A is 1.0 mol L^-1 , the concentration of A after 100 seconds would be-

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0.23 mol L-1
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0.18 mol L-1
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0.11 mol L-1
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0.13 mol L-1

The decomposition of sucrose follows the first-order rate law. For this decomposition, t_1/2 is 3.00 hours. The fraction of sample of sucrose that remains after 8 hours would be -

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0.13
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0.42
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0.16
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0.25

The decomposition of hydrocarbon follows the equation: k = (4.5 × 10¹¹s^–1) e^-28000K/T

The activation energy (E_a) for the reaction would be-

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232.79 kJ mol^-1
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245.86 kJ mol^-1
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126.12 kJ mol^-1
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242.51 kJ mol^-1

The rate constant for the first-order decomposition of H₂O₂ is given by the equation: log k = 14.34 – 1.25 × 10⁴ $\frac{K}{T}$ . The value of E_a for the reaction would be-

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249.34 kJ mol^-1
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242.64 J mol^-1
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-275.68 kJ mol^-1
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239.34 kJ mol^-1

$1 . 24 ° K 2 . 24 ° C 3 . 31 ° C 4 . 38 ° C$

The decomposition of A into the product has a value of k as 4.5 × 10³ s^–1 at 10°C and energy of activation of 60 kJ mol^–1. The temperature at which rate constant becomes 1.5 × 10⁴s^–1would be -

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The time required for 10% completion of a first order reaction at 298K is equal to that required for its 25% completion at 308K. If the value of A is 4 × 10¹⁰s^–1. What will be the activation energy for the reaction ?

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76.64 kJ mol^-1
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72.27 kJ mol^-1
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68.95 kJ mol^-1
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56.24 kJ mol^-1

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. The energy of activation of the reaction would be -

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65.93 kJ mol^-1
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52.85 kJ mol^-1
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55.46 kJ mol^-1
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60.93 kJ mol^-1

The role of a catalyst is to change -

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Gibbs energy of the reaction
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Enthalpy of reaction
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The activation energy of the reaction
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Equilibrium constant

In the presence of a catalyst, the heat evolved or absorbed during the reaction -

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Increases
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Decreases
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Remains unchanged
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May increase or decrease

Activation energy of a chemical reaction can be determined by -

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Determining the rate constant at standard temperature.
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Determining the rate constant at two temperatures.
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Determining probability of collision.
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Using the catalyst.

The correct statement among the following based on above mentioned graph is -

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Activation energy of forward reaction is $E_{1} + E_{2}$ and the product is less stable than reactant.
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Activation energy of forward reaction is $E_{1} + E_{2}$ and the product is more stable than the reactant.
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Activation energy of both forward and backward reaction is $E_{1} + E_{2}$ and reactant is more stable than the product.
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Activation energy of the backward reaction is E₁ and the product is more stable than reactant.

Consider a first-order gas-phase decomposition reaction given below

$A (g) \to B (g) + C (g)$

The initial pressure of the system before decomposition of A was $P_{i}$ . After the lapse of time, 't total pressure of the system increased by X units and became $P_{t}$ . The rate constant k for the reaction is given as -

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$k = \frac{2 .303}{t} \log \frac{P_{i}}{P_{i} - x}$
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$k = \frac{2 .303}{t} \log \frac{P_{i}}{2 P_{i} - P_{t}}$
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$k = \frac{2 .303}{t} \log \frac{P_{i}}{2 P_{i} + P_{t}}$
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$k = \frac{2 .303}{t} \log \frac{P_{i}}{P_{i} + x}$

The graph that represents the relation between ln k vs 1/T is :

Consider the Arrhenius equation given below and mark the correct option :

$k = A e^{- \frac{E_{a}}{R T}}$

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Rate constant increases exponentially with increasing activation energy and decreasing temperature.
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Rate constant decreases exponentially with increasing activation energy and decreasing temperature.
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Rate constant increases exponentially with decreasing activation energy and decreasing temperature.
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Rate constant increases exponentially with decreasing activation energy and increasing temperature.

A graph of volume of hydrogen released vs time for the reaction between zinc and dil. HCl is given in the graph below.

The correct statement among the following based on the graph given above is:

$1 . Average rate upto 40 s is \frac{V_{3} - V_{2}}{40} 2 . Average rate upto 40 s is \frac{V_{3} - V_{2}}{40 - 30} 3 . Average rate upto 40 s is \frac{V_{3}}{40} 4 . Average rate upto 40 s is \frac{V_{3} - V_{1}}{40 - 20}$

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Consider the graph given in the figure. Which of the following options does not show an instantaneous rate of reaction in the 40s?

$\begin{array}{llll} 1 \frac{V_{5} - V_{2}}{50 - 30} & 2 \frac{V_{4} - V_{2}}{50 - 30} & 3 \frac{V_{3} - V_{2}}{40 - 30} & 4 \frac{V_{3} - V_{1}}{40 - 20} \end{array}$

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The correct statement among the following options is:

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The rate of a reaction decreases with the passage of time as concentration of reactants decreases.
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The rate of a reaction is the same at any time during the reaction.
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The rate of a reaction is independent of temperature change.
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The rate of a reaction decreases with an increase in the concentration of the reactant(s).

The correct expression for the rate of reaction given below is :

$5 B r^{-} (a q) + B r O_{3}^{-} (a q) + 6 H^{+} (a q) \to 3 B r_{2} (a q) + 3 H_{2} O (I)$

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$\frac{∆ [B r^{-}]}{∆ t} = 5 \frac{∆ [H^{+}]}{∆ t}$
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$\frac{∆ [B r^{-}]}{∆ t} = \frac{6}{5} \frac{∆ [H^{+}]}{∆ t}$
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$\frac{∆ [B r^{-}]}{∆ t} = \frac{5}{6} \frac{∆ [H^{+}]}{∆ t}$
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$\frac{∆ [B r^{-}]}{∆ t} = 6 \frac{∆ [H^{+}]}{∆ t}$

The graph that represents an exothermic reaction amongst the following is :

(I)

(II)

(III)

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Only (I)
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Only (II)
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Only (III)
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Only (I) and (II)

Rate law for the reaction A+ 2B -> C is found to be

Rate = k[A][B]

The concentration of reactant 'B is doubled, keeping the concentration of A constant, the value of the rate of the reaction will be :

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The same.
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Doubled.
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Quadrupled.
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Halved.

Incorrect statement about the collision theory of chemical reaction is:

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It considers reacting molecules or atoms to be hard spheres and ignores their structural features.
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Number of effective collisions determines the rate of reaction.
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Collision of atoms or molecules possessing sufficient threshold energy results in product formation.
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Molecules should collide in the proper orientation for the collision to be effective with sufficient threshold energy and proper orientation.

A first-order reaction is 50% completed in 1.26 x $10^{14}$ s. Time required for 100% completion of reaction is :

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$1 .26 \times 10^{15} s$
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$2 .52 \times 10^{14} s$
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$2 .52 \times 10^{28} s$
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Infinite

Compounds A and B react according to the following chemical equation.

A(g) + 2B(g) $\overset{}{\to}$ 2C(g)

Experiment	Initial concentration of [A]/mol L^-1	Initial concentration of [B]/moI L^-1	Initial rate (mol L^-1 s^-1)
1. 2. 3.	0.30 0.30 0.60	0.30 0.60 0.30	0.10 0.40 0.20

$1 . Rate = k {[A]}^{2} [B] 2 . Rate = k [A] {[B]}^{2} 3 . Rate = k [A] [B] 4 . Rate = k {[A]}^{2} {[B]}^{0}$

The concentration of either A or B was changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. The following results were obtained. Choose the correct option for the rate equations for this reaction.

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Incorrect statement regarding catalyst is :

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It catalyzes the forward and backward reactions to the same extent.
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It alters gibbs free energy of the reaction.
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It is a substance that does not change the equilibrium constant of a reaction.
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It provides an alternate mechanism by reducing activation energy between reactants and products.

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Practice Chemistry Quiz Questions and Answers

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Practice Chemistry Quiz Questions and Answers

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