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CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 1 - MCQExams.com

The rate of a reaction quadruples when the temperature changes from 300 to 310 K. The activation energy of this reaction is :
(Assume activation energy and pre-exponential factor are independent of temperature; ln 2=0.693; R = 8.314 J mol1K1
  • 26.8 kJ mol1
  • 414.4 kJ mol1
  • 107.2 kJ mol1
  • 53.6 kJ mol1
Higher order (>3) reactions are rare due to:
  • low probability of simultaneous collision of all the reacting species
  • increase in entropy and activation energy as more molecules are involved
  • shifting of equilibrium towards reactants due to elastic collisions
  • loss of active species on collision
Activation energy of a reaction:
  • is independent of temperature
  • increase with temperature
  • gets double in every 10 degree raise in temperature
  • decrease with temperature
The decomposition of phosphine (PH3) on tungsten at low pressure is a first-order reaction. It is because the:
  • rate is independent of the surface coverage
  • rate of decomposition is very slow
  • rate is proportional to the surface coverage
  • rate is inversely proportional to the surface coverage
A first order reaction has a specific reaction rate of 102sec1. How much time will it take for 20 g of the reactant to reduce to 5 g?
  • 693.0 sec
  • 238.6 sec
  • 138.6 sec
  • 346.5 sec
  • Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
  • Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
  • Assertion is correct but Reason is incorrect
  • Both Assertion and Reason are incorrect
For a first order gas phase reaction: 

A(g)2B(g)+C(g)

P0 be initial pressure of A and P, the total pressure at time 't. Integrated rate equation is:
  • 2.303tlog(P0P0Pt)
  • 2.303tlog(2P03P0Pt)
  • 2.303tlog(P02P0Pt)
  • 2.303tlog(2P02P0Pt)
The thermal decomposition of HCOOH is a first-order reaction with a rate constant of 2.4×103s1 at certain temperature. How long will it take for three-fourths of the initial quantity of HCOOH to decompose?
  • 578 sec
  • 225 sec
  • 436 sec
  • 57.8 sec
In a homogeneous reaction AB+C+D the initial pressure was P0 and after time t it was P. Expression for rate constant k in terms of P0, P and t will be:
  • k=2.303tlog2P03P0P
  • k=2.303tlog2P0P0P
  • k=2.303tlog3P0P2P0
  • k=2.303tlog2P03P02P
What is the activation energy (KJ/mol) for a reaction if its rate constant doubles when the temperature is raised from 300K to 400K? (R=8.314 J mol1K1)
  • 68.8
  • 6.88
  • 34.4
  • 3.44
In a first order reaction with time the concentration of the reactant decreases:
  • Linearly
  • Exponentially
  • No change
  • None of these
Consider the two equations at a particular temperature ;
2N_2O_5\rightarrow 4NO_2+O_2

N_2O_5\rightarrow 2NO_2+\frac{1}{2}O_2

If E_1 and E_2 represents the activation energy for the first and second reaction respectively then :
  • E_1 > E_2
  • E_1 < E_2
  • E_1 = 2E_2
  • E_1 = E_2
A catalyst is a substance which
  • Increases the equilibrium constant of the reaction
  • Increases equilibrium concentration of products
  • Does not alter the reaction mechanism
  • Changes the activation energy of the reaction
2A\rightarrow B + C
It would be a zero order reaction when:
  • the rate of reaction is proportional to square of conc.of A.
  • the rate of reaction remains same at any conc.of A.
  • the rate remains unchanged at any conc.of B and C.
  • the rate of reaction doubles if conc. of B is increased to double.
On increasing the temperature by 10^{0}C:
  • number of collisions get doubled
  • value of rate constant does not change
  • energy of activation increases
  • number of fruitful collisions gets doubled
For which order reaction, the unit of rate constant is time^{-1}?
  • Zero order
  • First order
  • Second order
  • Third order
What happen with the rate of the reaction when the frequency and the number of effective collisions between reacting particles increases?
  • Increases
  • Decreases
  • Remains the same
  • Approaches zero
  • None of the above
While plotting decrease in mass against time, a flat curve shows:
  • fastest reaction.
  • reaction is slower.
  • reaction is over.
  • None of these.
Chemical kinetics a branch of physical chemistry deals with:
  • structure of molecules
  • heat changes in a reaction
  • physical changes in a reaction
  • rate of reactions
Which of the following theory is not related to the chemical kinetics?
  • Collision theory
  • Absolute theory
  • Absolute reaction rate
  • VSEPR theory
Reactants molecule must gain a minimum amount of energy called the _____________ before they can transform into product molecules.
  • activation energy
  • reaction energy
  • equilibrium energy
  • none of the above
Which increases average kinetic energy?
  • An increase in the reaction concentration
  • An increase in temperature
  • A decrease in pressure
  • Catalysis
  • \displaystyle pH
Chemical kinetics, a branch of physical chemistry, deals with:
  • heat changes in a reaction
  • physical changes in a reaction
  • rate of reactions
  • structure of molecules
For which of the following, the units of rate and rate constant of the reaction is identical?
  • First order reaction
  • Zero order reaction
  • Second order reaction
  • Fractional order reaction
What is activation energy?
  • It is the minimum amount of energy it takes to start a chemical reaction.
  • It is the maximum amount of energy it takes to start a chemical reaction.
  • It is the intermediate compound in a chemical reaction.
  • It is the energy needed for an exothermic reaction.
  • It is the energy needed for an endothermic reaction.
What causes an increase in effective collisions without increasing average energy?
  • An increase in the reactant concentration
  • An increase in the temperature
  • A decrease in pressure
  • Catalysts
A zero order reaction is one:
  • in which reactants do not react
  • in which one of the reactants is in large excess
  • whose rate is uniform and not affected by time
  • whose rate increases with time
For determining the graph of an elementary bimolecular reaction process, all of the following must be determined except:
  • the energy of the reactants.
  • the activation energy of the reaction.
  • the energy of the intermediate.
  • the energy of the products.
For the reaction shown, which best describes the elementary reaction?

2N_{2}O_{5}\leftrightharpoons 4NO_{2} + O_{2}
  • First order unimolecular
  • Second order unimolecular
  • Second order bimolecular
  • First order bimolecular
For zero order reaction, the integrated rate equation is:
  • kt=\cfrac{[A]}{[A]_o}
  • kt=[A]-[A]_o
  • [A]=-kt+[A]_o
  • [A]=kt-[A]_o
Half life for a  Ist order reaction { A\longrightarrow  } product , is 60minute. What % of A remains after120min?
  • 25 %
  • 50%
  • 75%
  • 90%
Wrong data for the first order reaction is:
  • { t }_{ 0.5 }=100s, { t }_{ 0.75 }=200s
  • { t }_{ 0.75 }=32 min,\ { t }_{ 0.5 }=16 min
  • both the above
  • { t }_{ 0.5 }=100s, { t }_{ 0.5 }=150s
The order and molecularity of the chain reaction, { H }_{ 2 }\left( g \right) +{ Cl }_{ 2 }\left( g \right) \xrightarrow [  ]{  \quad hv\quad  } 2HCl\left( g \right) , are:
  • 2, 0
  • 0, 2
  • 1, 1
  • 3, 0
Activation energy is:
  • the amount of energy to be added to the actual energy of a molecule so that the threshold energy is reached.
  • the amount of energy the molecule must contain so that it reacts.
  • the energy which a molecule should have in order to enter into an effective collision.
  • the average kinetic energy of the molecule.
If the door of a refrigerator is kept open in a dosed room then room:
  • heated
  • cooled
  • heated or cooled depending upon the initial temperature of the room
  • neither cooled nor heated
A zero-order reaction is one in which the rate of the reaction is independent of:
  • the temperature of the reaction
  • the concentration of the reactants
  • the concentration of the products
  • the volume of the vessel in which the reaction is carried out
The activation energy of a reaction is dependent on:
  • temperature
  • pressure
  • concentration
  • nature of reactants
The time for half change of a reactant in a zero order reaction is:
  • proportional to the initial concentration
  • proportional to the square root of the initial concentration
  • independent of initial concentration
  • inversely proportional to the initial concentration
The rate of chemical reaction depends on the nature of reactants because:
  • the number of bonds broken in the reactant molecules and the number of bonds formed in product molecules changes
  • some of the reactants are solids at the room temperature
  • some of the reactants are coloured
  • some of rectants are liquid at room temperature
If a reaction obeys the following equation k=\frac{2.303}{t}log\frac{a}{a-x} then the order is:


  • 0
  • 1
  • 2
  • 3
If the activation energy of both the forward and the backward reactions are equal. Then \Delta H of the reaction is:
  • zero
  • +ve
  • -ve
  • cannot be predicted
In a reaction between two gaseous reactants the number of binary collisions per second (Z) is given by:
  • Z=\pi \sigma ^{2}_{A-B}\sqrt{\frac{8KT}{\pi \mu }}n_{A}.n_{B}
  • Z=\pi \sigma _{A-B}\sqrt{\frac{8KT}{\pi \mu }}
  • Z= \sigma^{2} _{A-B}\sqrt{\frac{8KT}{\pi \mu }}n_{A}.n_{B}
  • Z= \sigma _{A-B}\sqrt{\frac{8KT}{\pi \mu }}n_{A}.n_{B}
If C_{o}=initial concentration of the reactant, C_{t}= concentration of the reactant at time t and k=rate constant of the reaction, then the equation applicable for a first order reaction is:
  • C_{t}=C_{0}e^{-Kt}
  • C_{t}=C_{0}e^{Kt}
  • C_{0}=C_{t}e^{-Kt}
  • \displaystyle\frac{C_{0}}{C_{t}}=1
In a first order reaction, the concentration of product 'x' at time 't' is given by the expression:
 (where,a = initial concentration, k = rate constant, n = order)
  • x=a\left ( 1-e^{-kt} \right )
  • x=\dfrac{1}{\left ( a-x \right )}
  • x=\dfrac{1}{2^{n-1}}
  • x=\dfrac{a}{\left ( a-x \right )}
In a first order reaction, fraction of the total concentration of the reactant that varies with time 't' is equal to:
  • e^{+kt}
  • 10^{+0.434kt}
  • \dfrac{1}{2^{-n}}
  • e^{-kt}
The threshold energy of a chemical reaction depends upon:
  • nature of reacting species
  • temperature
  • concentration of species
  • number of collisions
For producing the effective collisions, the colliding molecules must posses:

  • a certain minimum amount of energy
  • energy equal to greater than threshold energy
  • proper geometry
  • threshold energy and proper orientation
The value of energy of activation for radioactive decay is:
  • high
  • low
  • almost zero
  • moderate
The time required for the completion of first order reaction is:
  • infinity
  • thrice that of time required for 90% completion
  • 3/2 that of time required for 90% completion
  • ten times that of time required for 90% completion
The excess of energy required for the reactant molecules to undergo a reaction is:

  • Potential energy
  • Kinetic energy
  • Thermal energy
  • Activation energy
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