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 $$mol^{ -1} K^{-1}$$) 
  • 26.8 kJ $$mol^{-1}$$
  • 414.4 kJ $$mol^{-1}$$
  • 107.2 kJ $$mol^{-1}$$
  • 53.6 kJ $$mol^{-1}$$
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 $$(PH_3)$$ 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 $$10^{-2} sec^{-1}$$. 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: 

$$A_{(g)} \rightarrow 2B_{(g)} + C_{(g)}$$. 

$$P_{0}$$ be initial pressure of $$A$$ and $$P$$, the total pressure at time '$$t'$$. Integrated rate equation is:
  • $$\dfrac {2.303}{t}\log \left (\dfrac {P_{0}}{P_{0} - P_{t}}\right )$$
  • $$\dfrac {2.303}{t}\log \left (\dfrac {2P_{0}}{3P_{0} - P_{t}}\right )$$
  • $$\dfrac {2.303}{t}\log \left (\dfrac {P_{0}}{2P_{0} - P_{t}}\right )$$
  • $$\dfrac {2.303}{t}\log \left (\dfrac {2P_{0}}{2P_{0} - P_{t}}\right )$$
The thermal decomposition of $$HCOOH$$ is a first-order reaction with a rate constant of $$2.4\times {10}^{-3}{s}^{-1}$$ 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 $$A\longrightarrow B+C+D$$ the initial pressure was $${P}_{0}$$ and after time $$t$$ it was $$P$$. Expression for rate constant $$k$$ in terms of $${P}_{0},$$ $$P$$ and $$t$$ will be:
  • $$k=\cfrac { 2.303 }{ t } \log { \cfrac { 2{ P }_{ 0 } }{ { 3P }_{ 0 }-P } } $$
  • $$k=\cfrac { 2.303 }{ t } \log { \cfrac { 2{ P }_{ 0 } }{ { P }_{ 0 }-P } } $$
  • $$k=\cfrac { 2.303 }{ t } \log { \cfrac { { 3P }_{ 0 }-P }{ 2{ P }_{ 0 } } } $$
  • $$k=\cfrac { 2.303 }{ t } \log { \cfrac { 2{ P }_{ 0 } }{ { 3P }_{ 0 }-2P } } $$
What is the activation energy (KJ/mol) for a reaction if its rate constant doubles when the temperature is raised from $$300$$K to $$400$$K? $$(R=8.314$$ J $$mol^{-1}K^{-1}$$)
  • $$68.8$$
  • $$6.88$$
  • $$34.4$$
  • $$3.44$$
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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