CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 6 - MCQExams.com

Which of the following graphs is correct for the following reaction?
$$C{ H }_{ 3 }-C{ H }_{ 2 }-CH=C{ H }_{ 2 }\xrightarrow [ { 300 }^{ o }C ]{ \quad { { H }_{ 2 } }/{ Ni }\quad  } C{ H }_{ 3 }-C{ H }_{ 2 }-C{ H }_{ 2 }-C{ H }_{ 3 }$$
The rate of a reaction at $$10$$ sec intervals are as follows:
Time $$\left( sec \right) $$     Rate
$$\left( mol\ { L }^{ -1 }{ sec }^{ -1 } \right) $$
           $$0$$$$4.8\times { 10 }^{ -2 }$$
          $$10$$$$4.79\times { 10 }^{ -2 }$$
         $$20$$$$4.78\times { 10 }^{ -2 }$$
         $$30$$$$4.81\times { 10 }^{ -2 }$$
What will be the order of the reaction?
  • $$0$$
  • $$2$$
  • $$1$$
  • $$3$$
$$A$$ and $$B$$ are two different chemical species undergoing first order decompositions with half-life periods as $$3$$ and $$4.5$$ minutes respectively. If the initial concentrations of $$A$$ and $$B$$ are in the ratio $$1 : 2$$, The ratio $$C_{t_{(A)}}/ C_{t_{(B)}}$$ after three half-lives of $$A$$ would be:
  • $$3 : 4$$
  • $$1 : 1$$
  • $$1 : 4$$
  • $$4 : 3$$
The half-life period of a first order process is $$1.6$$min. It will be $$90\%$$ complete in :
  • $$5.3$$ min
  • $$10.6$$ min
  • $$43.3$$ min
  • $$99.7$$ min
Graph between $$\log { k } $$ and $$\cfrac{1}{T}$$ is a straight line with $$OX=5,\tan{\theta}=\left( \cfrac { 1 }{ 2.303 }  \right) $$. Hence $${E}_{a}$$ will be:
694240_260ca9074a5143fab9b5614ead4e89f2.JPG
  • $$2.303\times 2$$ cal
  • $$\cfrac { 5 }{ 2.303 } cal$$
  • $$-2$$
  • None of these
The activation energy for the forward reaction $$X\rightarrow Y$$ is $$60KJ$$ $${mol}^{-1}$$ and $$\Delta H$$ is $$-20KJ$$ $${mol}^{-1}$$. The activation energy for the backward reaction $$Y\rightarrow X$$ is:
  • $$80KJ$$ $${mol}^{-1}$$
  • $$40KJ$$ $${mol}^{-1}$$
  • $$60KJ$$ $${mol}^{-1}$$
  • $$20KJ$$ $${mol}^{-1}$$
$$N_2(g)+3H_2(g)\rightleftharpoons 2NH_3(g)+22$$ kcal. The activation energy for the forward reaction $$50$$ kcal. What is the activation energy for the backward reaction?
  • $$72$$ kcal
  • $$28$$ kcal
  • $$-72$$ kcal
  • $$-28$$ kcal
The unit , $$\\mol L^{-1} s^{-1} $$ is meant for the rate constant of the reaction having the order :
  • 0
  • 2
  • 1
  • 3
If for a reaction in which $$A(g)$$ converts to $$B(g)$$ the reaction carried out at const. $$V$$ and $$T$$ results into the following graph.
691581_87d77e23b22b4c27bbab4377f301797d.png
  • Then the reaction must be $$A(g) \rightarrow 3B(g)$$ and is a first order reaction
  • Then the reaction must be $$A(g) \rightarrow 3B(g)$$ and is a second order reaction
  • Then the reaction must be $$A(g) \rightarrow 3B(g)$$ and is a zero order reaction
  • Then the reaction must be $$A(g) \leftrightarrow 3B(g)$$ and is a first order reaction
A first order reaction is $$75 \% $$ completed in $$100 $$ minutes. How long time will it take for it's $$ 87.5 \% $$ completion?
  • $$125\ min$$
  • $$150\ min$$
  • $$175\ min$$
  • $$200\ min$$
In a reaction carried out at $$400\ K, 0.0001$$% of the total number of collisions are effective. The energy of activation of the reaction is:
  • zero
  • $$7.37\ kcal/mol$$
  • $$9.212\ kcal/mol$$
  • $$11.05\ k cal/mol$$
For the zero order reaction $$ A \rightarrow B + C ; $$ initial concentration of $$A$$ is $$ 0.1 M. $$ If $$A = 0.08 M $$ after $$10 $$ minutes, then it's half-life and completion time are respectively :
  • $$10$$ min $$ ; 20 $$ min
  • $$2 \times 10^{-3} $$ min $$ ; 4 \times 10^{-3} $$ min
  • $$25$$ min $$ ; 50 $$ min
  • $$250$$ min $$ ; 500 $$ min
In a first order reaction, the concentration of the reactant decreases from 0.8 M to 0.4 in 15 minutes. The time taken for the concentration to change from 0.1M to 0.025 M is:
  • 30 min
  • 40 min
  • 35 min
  • 25 min
A reaction takes place in three steps. The rate constants are $$k_{1}, k_{2}$$ and $$k_{3}$$. The over all rate constant $$k = \dfrac {k_{1}k_{3}}{k_{2}}$$. If (energy of activation) $$E_{1}, E_{2}$$ and $$E_{3}$$ are $$60, 30$$ and $$10\ kJ$$, the overall energy of activation is:
  • $$40$$
  • $$30$$
  • $$400$$
  • $$60$$
In bimolecular reaction, the steric factor $$P$$ was experimentally determined to be $$4.5$$. The correct option(s) among the following is (are):
  • the activation energy of the reaction is unaffected by the value of the steric factor
  • experimentally determined value of frequency factor is higher than that predicted by Arrheneius equation
  • since $$P=4.5$$, the reaction will not proceed unless an effective catalyst is used
  • tThe value of frequency factor predicted by Arrhenius equation is higher than that determined experimentally
Which graph represents the zero order reaction?

 $$A(g) \rightarrow B(g)$$.
A first order reaction has $$k = 1.5\times 10^{-6}$$ per second at $$200^0C$$. If the reaction is allowed to run for 10 hrs, what percentage of the initial concentration would have changed into the product? 
  • 5.213%
  • 10.21%
  • 20.3%
  • 15.2%
The half-life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is: 
  • 3.125 g
  • 2.084 g
  • 1.042 g
  • 4.167 g
Select incorrect statements : 
  • Pre exponential factor for zero order reaction is a unitless quantity
  • If $$t_{1/4}$$ = 30 sec then $$t_{1/2}$$ = 60 sec for first order reaction
  • If $$t_{1/3}$$ = 30 sec then $$t_{2/3}$$ = 90 sec for sec-order reaction
  • If $$t_{1/5}$$ = 30 sec then $$t_{3/5}$$ = 90 sec for zero order reaction.
First order reaction completes $$20\%$$ in $$5$$ min. How much time it will take for $$60\%$$ completion?
  • $$26.5$$ min
  • $$20.5$$ min
  • $$19.5$$ min
  • $$18$$ min
Cyclopropane rearranges to form propene:

$$\triangle \rightarrow CH_{2} - CH = CH_{2}$$

This follows first-order kinetics. The rate constant is $$2.714\times 10^{-3} sec^{-1}$$. The initial concentration of cyclopropane is $$0.29\ M$$. What will be the concentration of cyclopropane after $$100\ sec$$?
  • $$0.035\ M$$
  • $$0.22\ M$$
  • $$0.145\ M$$
  • $$0.0018\ M$$
The reaction $$2X \rightarrow Y + Z$$ would be zero order reaction when:
  • rate remains unchanged at any concentration of $$Y$$ and $$Z$$
  • rate of reaction doubles if concentration of $$Y$$ is doubled
  • rate of reaction remains same at any concentration of $$X$$
  • rate of reaction of directly proportional to square of concentration of $$X$$
In a zero order reaction, 20% of the reaction complete in 10 s. How much time it will take to complete 50% of the reaction ?
  • 20 s
  • 25 s
  • 30 s
  • 40 s
For the first order reaction,
$$2H_2O_2\rightarrow 2H_2\,+\,O_2 \,\log k\,=\,14.34\,-\,1.25\,\times\,10^4\,K/T$$. The energy of activation for the above reaction if its half life period is 256 min.
  • 400 KJ / mole
  • 230 KJ / mole
  • 480 KJ / mole
  • 239 KJ / mole
At low pressure, the fraction of the surface covered follows:
  • zero-order kinetics
  • first order kinetics
  • second order kinetics
  • fractional order kinetics
The following data were obtained during the first order thermal decomposition of $$SO_2Cl_2$$ at constant volume
$$SO_2Cl_{2(g)} \rightarrow SO_{2(g)}\,+\,Cl_{2(g)}$$
ExptTime / $$S^{-1}$$Total pressure/ atm
100.5
21000.6
when the total pressure is 0.65 atm then the rate constant of reaction is ..............
 if a = pi, and a - x = 2pi - Pt
  • 2.0 x $$10^{-3}\,S^{-1}$$
  • 2.12 x $$10^{-3}\,S^{-1}$$
  • 2.23 x $$10^{-3}\,S^{-1}$$
  • 2.34 x $$10^{-3}\,S^{-1}$$
The rate constant of a first order reaction is $$15\times 10^{-3} s^{-1}$$. How long will $$5.0\ g$$ of this reactant take to reduce to $$3.0\ g$$?
  • $$34.07\ s$$
  • $$7.57\ s$$
  • $$10.10\ s$$
  • $$15\ s$$
A first order reaction takes $$40$$ min for $$30$$% decomposition. What will be $$t_{1/2}$$?
  • $$77.7\ min.$$
  • $$52.5\ min.$$
  • $$46.2\ min.$$
  • $$22.7\ min.$$
The half-life of the reaction $$X\rightarrow Y$$, following first-order kinetics, when the initial concentration of $$X$$ is $$0.01$$ mol L$$^{-1}$$ and the initial rate is $$0.00352$$ mol L$$^{-1}$$ min$$^{-1}$$ will be :
  • $$19.60\ min$$
  • $$1.969\ min$$
  • $$7.75\ min$$
  • $$77.5\ min$$
The potential energy diagram for a reaction $$X\rightarrow Y$$ is given. $$A$$ and $$C$$ in the graph corresponds to:
934445_16d2975d9c974d9caf991d6423296f10.jpg
  • $$A \rightarrow$$ activation energy, $$C\rightarrow \triangle H^{\circ}$$
  • $$A\rightarrow$$ energy of reactants, $$C \rightarrow$$ energy of products
  • $$A\rightarrow \triangle H^{\circ}, C\rightarrow$$ activation energy
  • $$A\rightarrow$$ activation energy, $$C\rightarrow$$ threshold energy
The decomposition of a substance follows first order kinetics. If its concentration is reduced to $$1/8$$ of its initial value in $$12$$ minutes, the rate constant of the decomposition system is ?
  • $$\left (\dfrac {2.303}{12}\log \dfrac {1}{8}\right ) min.^{-1}$$
  • $$\left (\dfrac {2.303}{12}\log 8\right ) min.^{-1}$$
  • $$\left (\dfrac {0.693}{12}\right ) min.^{-1}$$
  • $$\left (\dfrac {1}{12}\log 8\right )min.^{-1}$$
Graph 9c) An endothermic reaction with high activation energy for the forward reaction can be shown by the figure:
What will be the half-life of the first order reaction for which the value of rate constant is $$200\ s^{-1}$$?
  • $$3.46\times 10^{-2} s$$
  • $$3.46\times 10^{-3} s$$
  • $$4.26\times 10^{-2} s$$
  • $$4.26\times 10^{-3} s$$
The activation energy in a chemical reaction is defined as ?
  • The difference in energies of reactants and products
  • The sum of energies of reactants and products
  • The difference in energy of intermediate complex with the average energy of reactants and products
  • The difference in energy of intermediate complex and the average energy of reactants
A first order reaction has a rate constant $$1.15\times 10^{-3}s^{-1}$$. How long will $$5\ g$$ of this reactant take to reduce to $$3\ g$$?
  • $$444\ s$$
  • $$400\ s$$
  • $$528\ s$$
  • $$669\ s$$
The rate constant for a first order reaction is $$2\times 10^{-2} min^{-1}$$. The half-life period of reaction is ?
  • $$69.3\ min.$$
  • $$34.65\ min.$$
  • $$17.37\ min.$$
  • $$3.46\ min.$$
In a first order reaction, the concentration of reactant is reduced to $$1/8$$ of the initial concentration in $$75$$ minutes at $$298\ K$$. What is the half-life period of the reaction in minutes?
  • $$50\ min$$
  • $$15\ min$$
  • $$30\ min$$
  • $$25\ min$$
Activation energy of a chemical reaction can be determined by _________.
  • determining the rate constant at standard temperature
  • determining the rate constants at two temperatures
  • determining probability of collision
  • using catalyst
The rate constant is given by the equation $$k = P.Ze^{-E_{a}/RT}$$. Which factor should register $$a$$ decrease for the reaction to proceed more rapidly:
  • $$T$$
  • $$Z$$
  • $$E$$
  • $$P$$
Fill up the following with suitable terms.

(i) Activation energy $$=$$ Threshold energy $$-$$ _______.

(ii) Half-life period of zero order reaction $$=$$ ________.

(iii) Average rate of reaction $$=$$ _______.

(iv) Instantaneous rate of reaction $$=$$ ______.
  • Potential energy, $$\dfrac {0.693}{k}, \dfrac {dx}{dt}, \dfrac {\triangle [A]}{\triangle t}$$
  • Energy of reactants, $$\dfrac {1}{k}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$$
  • Energy of reaction, $$\dfrac {\log k}{t}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$$
  • Average kinetic energy of reactants, $$\dfrac {a}{2k}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$$
A first order reaction is $$50$$% complete in $$30$$ minutes at $$27^{\circ}C$$ and in $$10$$ minutes at $$47^{\circ}C$$. The reaction rate constant at $$27^{\circ}C$$ and the energy of activation of the reaction are respectively.
  • $$k = 0.0231\ min^{-1}, E_{a} = 43.848\ kJ\ mol^{-1}$$
  • $$k = 0.017\ min^{-1}, E_{a} = 52.54\ kJ\ mol^{-1}$$
  • $$k = 0.0693\ min^{-1}, E_{a} = 43.848\ kJ\ mol^{-1}$$
  • $$k = 0.0231\ min^{-1}, E_{a} = 28.92\ kJ\ mol^{-1}$$
Threshold energy is equal to:
  • Activation energy
  • Activation energy $$-$$ energy of molecules
  • Activation energy $$+$$ energy of molecules
  • None of these
If hydrogen and oxygen are mixed and kept in the same vessel at room temperature, the reaction does not take place to form water because:
  • activation energy for the reaction is very high at room temperature
  • molecules have no proper orientation to react to form water
  • the frequency of collisions is not high enough for the reaction to take place
  • no catalyst is present in the reaction mixture
The decomposition of a hydrocarbon follows the equation $$k = (4.5\times 10^{11}s^{-1})e^{-28000/ K/T}$$. What will be the value of activation energy?
  • $$669\ kJ\ mol^{-1}$$
  • $$232.79\ kJ\ mol^{-1}$$
  • $$4.5\times 10^{11}\ kJ\ mol^{-1}$$
  • $$28000\ kJ\ mol^{-1}$$
The half-life period of an 1st order reaction is $$60$$ minutes. What percentage will be left over after $$240$$ minutes?
  • $$6.25\%$$
  • $$4.25\%$$
  • $$5\%$$
  • $$6\%$$
What is the half-life of a radioactive substance if $$87.5\%$$ of any given amount of the substance disintegrate in $$40$$ minutes?
  • $$160$$ min
  • $$10$$ min
  • $$20$$ min
  • $$13$$ min 
For an elementary bi-molecular reaction of the type $$A + B \rightarrow C$$ activation energy is equal to 20 Kcal. If specific rate of reaction at 500 K is 4.2 $$\times$$ $$10^{-3}M^{-1}sec^{-1}$$, then identify the incorrect option(s). [Given : ln ($$2.1 \times$$ $$10^{-9}$$) = - 20] 
  • % of activated molecules at 500 K is $$2.1 \times$$ $$10^{-7}$$%
  • Maximum possible rate of reaction when $$[A]$$ and $$[B]$$ are both equal to 1 is $$2 \times$$ $$10^6 M sec^{-1}$$
  • % of activated molecules at 300 K is $$2 \times 10^{-6}$$%
  • At some temperature rate of reaction can be $$4 \times 10^3 M sec^{-1}$$ if $$[A] =\ 2M,\ [B] = 0.1 M$$
The activation energy for the forward reaction X Y is $$60$$ KJ $$mol^{-1}$$ and $$\Delta H$$ is $$-20$$ KJ $$mol^{-1}$$. The activation energy for the backward reaction Y X is:
  • $$80$$ kJ $$mol^{-1}$$
  • $$40$$ kJ $$mol^{-1}$$
  • $$60$$ kJ $$mol^{-1}$$
  • $$20$$ kJ $$mol^{-1}$$
The half life for the first order reaction, $$N_2O_5\rightarrow 2NO_2+1/2O_2$$ is $$24$$ hours at $$30^o$$C. Starting with $$10$$g of $$N_2O_5$$, how many grams of $$N_2O_5$$ will remain after a period of $$96$$ hours?
  • $$1.25$$ g
  • $$0.63$$ g
  • $$1.77$$ g
  • $$0.5$$ g
Following reaction are of first order 
$$A\xrightarrow [  ]{ { k }_{ 1 }=2{ sec }^{ -1 } } 2B$$
$$A\xrightarrow [  ]{ { k }_{ 2 }=5{ sec }^{ -1 } } 3C$$
Which of the following statement $$(s)$$ is/are correct?
  • $$ \dfrac { { \left[ B \right] }_{ t } }{ { \left[ C \right] }_{ t } } =\dfrac { 2 }{ 5 }$$ at any time during reaction.
  • After completion of reaction $$\dfrac { { \left[ B \right] } }{ { \left[ C \right] } } =\dfrac { 2 }{ 15 } $$
  • $$ \dfrac { { \left[ B \right] }_{ t } }{ { \left[ C \right] }_{ t } } =\dfrac { 4 }{ 15 }$$ at any time during reaction
  • None of these
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