CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 5 - MCQExams.com

Here is another look at the reaction of crystal violet with sodium hydroxide, a first-order reaction (ln $$A$$ v time).
What is the significance of the slope?
537147.jpg
  • The slope represents the change in concentration over time.
  • The slope represents the inverse of change in concentration over time.
  • The slope represents the negative value of the rate constant.
  • The slope represents the negative rate of product concentration over time.
A graph of concentration versus time data for a first-order reaction gives a straight line in which of the following plots of the data?
  • $$[A]_{t} = -kt + [A]_{0}$$
  • $$ln [A]_{t} = -kt + ln [A]_{0}$$
  • $$\dfrac {1}{[A]_{t}} = kt + \dfrac {1}{[A]_{0}}$$
  • All of the above
  • None of the above
In a reaction mechanism consisting of elementary reaction steps where the relative rate of each is given, which of the following is most likely to be the rate-determining step?
  • A step labeled fast
  • A step labeled moderate
  • A step labeled slow
  • It is not possible to tell which step is rate determining from this information.
Reacting $$Cl$$ with $$NO_{2}Cl$$ molecules produces $$NO_{2}$$ and $$Cl_{2}$$ gases.
Which of the following will require the lowest activation energy based on proper orientation for this reaction?
An experiment was performed to study the kinetics of the decomposition of substance $$X$$. The concentration of $$X$$, $$[X]$$, was monitored over time as the reaction proceeded. The data are shown in the table above. The time interval between concentration measurements was $$1.0\ minutes (60 s)$$.
Time (s)$$[X]$$$$ln[X]$$$$\dfrac {1}{[X]}$$
$$0$$$$20.0$$$$3.00$$$$0.050$$
$$60$$$$10.0$$$$2.30$$$$0.100$$
$$120$$$$6.67$$$$1.90$$$$0.150$$
$$180$$$$5.00$$$$1.61$$$$0.200$$
$$240$$$$4.00$$$$1.39$$$$0.250$$
Which of the following best describes the reaction?
  • The decomposition of substance $$X$$ is a zero-order reaction.
  • The decomposition of substance $$X$$ is a first-order reaction.
  • The decomposition of substance $$X$$ is a second-order reaction.
  • The decomposition of substance $$X$$ is a third-order reaction.
In a given reaction under standard conditions in a closed container, which type of reaction would show no real increase in the rate of the reaction when the concentration of each reactant is doubled?
  • A zero order
  • A first order
  • A second order
  • A third order
A first order reaction is 60% complete in 20 minutes. How long will the reaction take to be 84% complete?
  • 54 mins
  • 68 mins
  • 40 mins
  • 76 mins
A plot of $$\dfrac { 1 }{ T } $$ vs. $$logk$$ for a reaction gives the slope $$(-1\times { 10 }^{ 4 }\ K)$$. The energy of activation for the reaction is :
(Given $$R=8.314\ J{ K }^{ -1 }{ mol }^{ -1 }$$)
  • $$1.202\ kJ{ mol }^{ -1 }$$
  • $$83.14\ kJ{ mol }^{ -1 }$$
  • $$8314\ J { mol }^{ -1 }$$
  • $$191.47 \ kJ mol^{-1}$$
The correct statement regarding the following energy diagrams is
574099_0e97e890a2f646b7beb83e8cd4a626ab.png
  • Reaction M is faster and less exothermic than Reaction N
  • Reaction M is slower and less exothermic than Reaction N
  • Reaction M is faster and more exothermic than Reaction N
  • Reaction M is slower and more exothermic than Reaction N
The activation energy of a chemical reaction can be determined by :
  • evaluating rate constants at two different temperatures
  • changing the concentration of reactants
  • evaluating the concentration of reactants at two different temperatures
  • evaluating rate constant at standard temperature
A given sample of milk turns sour at room temperature $$(27 ^oC)$$ in 5 hours. In a refrigerator at $$-3 ^oC$$, it can be stored 10 times longer. The energy of activation for the souring of milk is :
  • $$2.303 \times 10 R \ \ kJ \cdot mol^{-1}$$
  • $$2.303 \times 5 R \ \ kJ \cdot mol^{-1}$$
  • $$2.303 \times 3 R \ \ kJ \cdot mol^{-1}$$
  • $$2.303 \times 2.7 R \  \ kJ \cdot mol^{-1}$$
When the concentration of a reactant of first order reaction is doubled, the rate becomes ________ times, but for ___________ order reaction, the rate remains same.
  • Four; zero
  • Two; zero
  • Zero; four
  • Zero; three
The unit of zero order rate constant is:
  • $$litre$$ $$mol^{-1} sec^{-1}$$
  • $$mol$$ $$litre^{-1} sec^{-1}$$
  • $$sec^{-1}$$
  • $$litre^{2} sec^{-1}$$
The excess energy which a molecule must posses to become active is known as:
  • kinetic energy
  • threshold energy
  • potential energy
  • activation energy
The unit of rate constant for zero order reaction is:
  • $$s^{-1}$$
  • $$mol\, L^{-1}s^{-1}$$
  • $$L\, mol^{-1}s^{-1}$$
  • $$L^2mol^{-2}s^{-1}$$
Which graph shows zero activation energy for reaction?
For a zero-order reaction with a rate constant k, the slope of the plot of reactant concentration against time is:
  • $$\dfrac{ k} {2.303}$$
  • $$k$$
  • $$-\dfrac {k}{2.303}$$
  • $$-k$$
The relationship between rate constant and half-life period of zero-order reaction is given by:
  • $${ t }_{ \frac { 1 }{ 2 } }={ \left[ A \right] }_{ 0 }2k$$
  • $${ t }_{ \frac { 1 }{ 2 } }=\dfrac { 0.693 }{ k } $$
  • $${ t }_{ \frac { 1 }{ 2 } }=\dfrac { { \left[ A \right] }_{ 0 } }{ 2k } $$
  • $${ t }_{ \frac { 1 }{ 2 } }=\dfrac { 2{ \left[ A \right] }_{ 0 } }{ k } $$
The half-life of $$^{14}C$$ is 5570 yr. How many years will it take 90% of a sample to decompose?
  • 5,570 yr
  • 17,700 yr
  • 18,510 yr
  • 50,100 yr
Collision theory is applicable to 
  • First order reactions
  • Zero order reactions
  • Bimolecular reactions
  • Intramolecular reactions
$$3A\longrightarrow B+C$$

It would be a zero-order reaction when:
  • The rate of reaction is proportional to square of concentration of $$A$$
  • The rate of reaction remains the same at any concentration of $$A$$
  • The rate remains unchanged at any concentration of $$B$$ and $$C$$
  • The rate of reaction doubles if concentration of $$B$$ is increased to double
A certain radioactive isotope decay has $$\alpha$$-emission,
$$ _{ { Z }_{ 1 } }^{ { A }_{ 1 } }{ X }\longrightarrow $$ $$_{ { Z }_{ 1 }-2 }^{ { A }_{ 1 }-4 }{ Y }$$
half life of $$X$$ is $$10$$ days. If $$1$$ $$mol$$ of $$X$$ is taken initially in a sealed container, then what volume of helium will be collected at STP after $$20$$ days?
  • $$22.4 L$$
  • $$11.2 L$$
  • $$16.8 L$$
  • $$33.6 L$$
One gram of $$^{ 226 }{ Ra }$$ has an activity of nearly $$1 Ci$$. The half life of $$^{ 226 }{ Ra }$$ is
  • $$1582$$ yrs
  • $$12.5$$ hrs
  • $$140$$ days
  • $$4.5\times { 10 }^{ 9 }$$ yrs
The order of reaction for which half-life period is independent of initial concentration is:
  • zero
  • first
  • second
  • third
A freshly prepared radio medicine has half life $$2$$ hours. Its activity is $$64$$ times the permissible safe value. The minimum time after which it would be possible to treat the patients with the medicine is:
  • $$3$$ hrs
  • $$9$$ hrs
  • $$24$$ hrs
  • $$12$$ hrs
For an endothermic reaction, where $$\Delta H$$ represents the enthalpy of reaction, the minimum value for the energy of activation will be:
  • less than $$\Delta H$$
  • zero
  • equal to $$\Delta H$$
  • more than $$\Delta H$$
A first-order reaction has a half-life of $$14.5\ hrs$$. What percentage of the reactant will remain after $$24\ hrs$$?
  • $$18.3$$%
  • $$31.8$$%
  • $$45.5$$%
  • $$68.2$$%
The rates of a certain reaction at different time intervals are as follows:
$$\begin{matrix} Time(second) & 0 & 10 & 20 \\ Rate(mol\ L^{-1}s^{-1}) & 1.8\times { 10 }^{ -2 } & 1.82\times { 10 }^{ -2 } & 1.79\times { 10 }^{ -2 } \end{matrix}$$
The reaction is of:
  • zero order
  • first order
  • second order
  • third order
Which one of the following is not a first order reaction?
  • $$C{ H }_{ 3 }COOC{ H }_{ 3 }+{ H }_{ 2 }O\xrightarrow [ ]{ \quad { H }^{ + }\quad } C{ H }_{ 3 }COOH+C{ H }_{ 3 }OH$$
  • $$C{ H }_{ 3 }COO{ C }_{ 2 }{ H }_{ 5 }+NaOH\longrightarrow C{ H }_{ 3 }COONa+{ C }_{ 2 }{ H }_{ 5 }OH$$
  • $$2{ H }_{ 2 }{ O }_{ 2 }\longrightarrow 2{ H }_{ 2 }O+{ O }_{ 2 }$$
  • $$2{ N }_{ 2 }{ O }_{ 5 }\longrightarrow 4N{ O }_{ 2 }+{ O }_{ 2 }$$
Reaction, $$A+B\longrightarrow C+D+38kcal$$ has activation energy $$20kcal$$. Activation energy for the reaction, $$C+D\longrightarrow A+B\quad $$ is:
  • $$20kcal$$
  • $$-20kcal$$
  • $$18kcal$$
  • $$58kcal$$
At $$500$$ $$K$$, the half-life period of a gaseous reaction at an initial pressure of $$80$$ $$kPa$$ is $$350$$ $$sec$$. When the pressure is $$40$$ $$kPa$$, the half life period is $$175$$ $$sec$$; the order of the reaction is:
  • Zero
  • One
  • Two
  • Three
Which of the following is a first order reaction?
  • $$2HI\longrightarrow { H }_{ 2 }+{ I }_{ 2 }$$
  • $$2N{ O }_{ 2 }\longrightarrow 2NO+{ O }_{ 2 }$$
  • $$2NO+{ O }_{ 2 }\longrightarrow 2N{ O }_{ 2 }$$
  • $$N{ H }_{ 4 }N{ O }_{ 2 }\longrightarrow { N }_{ 2 }+2{ H }_{ 2 }O$$
A substance reacts with initial concentration of $$a$$ $$mol$$ $${ dm }^{ -3 }$$ according to zero order kinetics. The time it takes for the completion of the reaction is: ($$k=$$ rate constant)
  • $$\dfrac { k }{ a } $$
  • $$\dfrac { a }{ 2k } $$
  • $$\dfrac { a }{ k } $$
  • $$\dfrac { 2k }{ a } $$
The decomposition of $$HI$$ on the surface of gold is:
  • pseudo first order
  • zero order
  • first order
  • second order
For a zero order reaction which of the following relation is correct, where $$t_{1/2}\ and\ a$$ are half-life and initial concentration respectively.
  • $${ t }_{ { 1 }/{ 2 } }\propto a$$
  • $${ t }_{ { 1 }/{ 2 } }\propto \dfrac { 1 }{ a } $$
  • $${ t }_{ { 1 }/{ 2 } }\propto { a }^{ 2 }$$
  • $${ t }_{ { 1 }/{ 2 } }\propto \dfrac { 1 }{ { a }^{ 2 } } $$
A drop of solution (volume $$0.05$$ $$mL$$) contains $$3\times { 10 }^{ -6 }$$ mole of $${ H }^{ + }$$. If the rate constant of disappearance of $${ H }^{ + }$$ is $${ 10 }^{ 7 }$$ $$mol$$ $${ litre }^{ -1 }$$ $${ sec }^{ -1 }$$, how long would it take for $${ H }^{ + }$$ in the drop to disappear?
  • $$6\times { 10 }^{ -8 }\ sec$$
  • $$6\times { 10 }^{ -9 }\ sec$$
  • $$6\times { 10 }^{ -10 }\ sec$$
  • $$6\times { 10 }^{ -12 }\ sec$$
The specific rate constant of a first order reaction depends on:
  • concentration of the reactants
  • concentration of the products
  • time
  • temperature
The rate constant of a reaction is found to be $$3\times { 10 }^{ -3 }$$ $$mol$$ $${ L }^{ -1 }$$ $${ min }^{ -1 }$$. The order of the reaction is:
  • $$0$$
  • $$1$$
  • $$2$$
  • $$1.5$$
The hydrolysis of ethyl acetate is a reaction of:
$$C{ H }_{ 3 }COO{ C }_{ 2 }{ H }_{ 5 }+{ H }_{ 2 }O\xrightarrow [  ]{ \quad { H }^{ + }\quad  } C{ H }_{ 3 }COOH+{ C }_{ 2 }{ H }_{ 5 }OH$$
  • zero order
  • first order
  • second order
  • third order
Graph between the concentration of the product '$$x$$' and time '$$t$$' for $$A\rightarrow B$$ is given above.
The graph between $$-\dfrac { d\left[ A \right]  }{ dt } $$ and time $$'t'$$ will be of the type:
661676_f86ebdaf4de04d2094016199e6fb6cb2.png
For a zero order reaction, $$A\longrightarrow P$$, $${ t }_{ { 1 }/{ 2 } }$$ is: 
($$k$$ is the rate constant, $$[A]_0$$ is the initial concentration of $$A$$)
  • $$\dfrac { { \left[ A \right] }_{ 0 } }{ 2k } $$
  • $$\dfrac { \ln { 2 } }{ k } $$
  • $$\dfrac { 1 }{ k{ \left[ A \right] }_{ 0 } } $$
  • $$\dfrac { \ln { 2 } }{ { \left[ A \right] }_{ 0 }k } $$
Following is the graph between $$\log{{ t }_{ { 1 }/{ 2 } }}$$ and $$\log { a } $$ ($$a=$$ initial concentration) for a given reaction at $${ 27 }^{ o }C$$. Hence, order of the reaction is:
661674_e8e498a2a5d14537967fbe6899017dc7.png
  • $$0$$
  • $$1$$
  • $$2$$
  • $$3$$
When the initial concentration of the reaction is doubled, the half-life is also doubled. The order of the reaction will be:
  • $$0$$
  • $$1$$
  • $$2$$
  • $$3$$
A substance having rate constant $$k$$ and initial concentration $$a$$ reacts according to zero order kinetics. What will be the time for the reaction to go to completion?
  • $$\dfrac { a }{ k } $$
  • $$\dfrac { k }{ a } $$
  • $$\dfrac { a }{ 2k } $$
  • $$\dfrac { 2k }{ a } $$
The time for half-life period of a certain reaction, $$A\rightarrow $$ Product, is $$1$$ hour, when the initial concentration of the reactant '$$A$$' is $$2$$ $$mol$$ $${ L }^{ -1 }$$. How much time does it take for its concentration to come from $$0.50$$ to $$0.25$$ $$mol$$ $${ L }^{ -1 }$$ if it is a zero order reaction?
  • $$0.25\ hr$$
  • $$1\ hr$$
  • $$4\ hrs$$
  • $$0.5\ hr$$
Raw milk sours in about 4 h at $$27^ o C$$, but in about 48 h in a refrigerator at $$17^ o C$$. What is the activation energy for souring of milk ?
  • 78.3 kJ $$mol^{-1}$$
  • 46.21 kJ $$mol^{-1}$$
  • 23.5 kJ $$mol^{-1}$$
  • 80.8 kJ $$mol^{-1}$$
Which of the following is not correct for zero order reaction?
In the reaction, $$A+B\longrightarrow C+D$$, the rate $$\left( \dfrac { dx }{ dt }  \right) $$ when plotted against time '$$t$$' gives a straight line parallel to time axis and at some time $$'t'$$, $$\dfrac{dx}{dt}=k$$. The order and rate of reaction will be:
  • $$1, k+1$$
  • $$0, k$$
  • $$\left( 1+k \right) , 1$$
  • $$k, k+1$$
$$N_2+3H_2\rightleftharpoons 2NH_3 +22$$kcal
The activation energy for the forward reaction is $$50$$kcal. What is the activation energy for the backward reaction?
  • $$-72$$ kcal
  • $$-28$$ kcal
  • $$+28$$ kcal
  • $$+72$$ kcal
For the first order reaction, $$t_{99}$$% $$= x \times t_{90}$$%, the value of $$x$$ will be: 
  • 10
  • 6
  • 3
  • 2
0:0:1


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