CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 9 - MCQExams.com

What is the activation energy for a reaction if the rate doubles when the temperature is raised from $$20^{o}C$$ to $$35^{o}C$$? $$(R=8.134\ J\ mol^{-1}K^{-1})$$
  • $$15.1\ kJ\ mol^{-1}$$
  • $$342\ kJ\ mol^{-1}$$
  • $$269\ kJ\ mol^{-1}$$
  • $$34.7\ kJ\ mol^{-1}$$
K for a zero order reaction is $$2\times10^{-2}\,mol\,L^{-1}sec^{-1}$$. If the concentration of the reactant after 25 sec is 0.5 M, the initial concentration must have been:
  • 0.5 M
  • 1.25 M
  • 12.5 M
  • 1.0 M
For a first order process $$A\rightarrow B$$ rate constant $${k}_{1}=0.693\ {min}^{-1}$$ and another first order process $$C\rightarrow D$$, $${K}_{2}=x$$ $${min}^{-1}$$. If $$99.9$$% of $$C\rightarrow D$$ requires time same as $$50$$% of reaction $$A\rightarrow B$$, value of $$x$$? (in $${min}^{-1}$$)
  • $$0.0693$$
  • $$6.93$$
  • $$23.03$$
  • $$13.86$$
The temperature coefficient of a reaction is $$2$$. When the temperature is increased from $$30^{\circ}C$$ to $$90^{\circ}C$$, the rate of reaction is increased by
  • $$150$$ times
  • $$410$$ times
  • $$72$$ times
  • $$64$$ times
A reaction $$A+B\leftrightarrow C+D$$  follows the mechanism:
$$A+B\leftrightarrow AB$$
$$AB+C\leftrightarrow D$$
In which first step remains essentially in equilibrium. If $$\Delta H$$ is the enthalpy change for the first reaction the activation energy for the second reaction, the activation energy of the overall reaction will be given? 
  • $$E_{0}$$
  • $$E_{0}-\Delta H$$
  • $$E_{0}+\Delta H$$
  • $$E_{0}+2\Delta H$$
If reaction A and B are given with Same temperature and same concentration but rate of $$A$$ is double than $$B$$. Pre exponential factor is same for both the reaction then difference in activation energy $$E_{A} - E_{B}$$ is?
  • $$-RT\ ln2$$
  • $$RT\ ln2$$
  • $$2RT$$
  • $$\dfrac {RT}{2}$$

Among the following, the maximum covalent character is shown by the compound
  • $$MgCl_{2}$$

  • $$FeCl_{2}$$

  • $$SnCl_{2}$$
  • $$AlCl_{3}$$
Raw milk sours in 4 hours at $$27^\circ C,$$ but in 40 hours in refrigerator at $$7^\circ C.$$ What is activation energy for souring of milk:
  • 402.1 J/mol
  • 30.2 J/mol
  • 8.04 KJ/mol
  • 80.4 KJ/mol
Two substances $$A$$ and $$B$$ are initially present as $$\left[ { A }_{ 0 } \right] =8\left[ { B }_{ 0 } \right] $$ and $${ t }_{ 1/2 }$$ for the first-order decomposition of $$A$$ and $$B$$ are $$10$$ and $$20$$ min, respectively. If they start decomposing at the same time, after how much time, the concentration of both of them would be same?
  • $$20min$$
  • $$40min$$
  • $$60min$$
  • $$200min$$
The decomposition of $${ NH }_{ 3 }$$ on nitrogen surface follows zero-order kinetics. The half-life is $$315s$$ for an initial pressure of $$70mm$$ of $${NH}_{3}$$. If the initial pressure had been $$150mm$$, what would be the half-life?
  • $$315s$$
  • $$472.5s$$
  • $$675s$$
  • $$630s$$
For the reaction : $$ NH_2COONH_4(s) \leftrightharpoons 2NH_3(g) +CO_2(g) , K_p = 3.2 \times 10^{-5}atm^3 $$
the total pressure of the gaseous products when sufficient amount of reactant is allowed to achieve equilibrium , is:
  • $$0.02$$ atm
  • $$0.04$$ atm
  • $$0.06$$ atm
  • $$0.095$$ atm
$$k$$ for a zero order reaction is $$2\times 10^{-2}\ mol\ L^{-1}\ s^{-1}$$. If the concentration of the reactant after $$25\ s$$ is $$0.5\ M$$, the initial concentration must have been:
  • $$0.5\ M$$
  • $$1.25\ M$$
  • $$12.5\ M$$
  • $$1.0\ M$$
$${ SO }_{ 2 }{ Cl }_{ 2 }\rightarrow { SO }_{ 2 }+{ Cl }_{ 2 }$$ is a first-order gaseous reaction with $$K=2.5\times { 10 }^{ -5 }{ s }^{ -1 }$$ at $${320}^{o}C$$. The percentage of $${ SO }_{ 2 }{ Cl }_{ 2 }$$ decomposed on heating for $$100min$$ is:
$$\left( \ln { 1.16 } =0.15 \right) $$
  • $$86.2$$
  • $$15.0$$
  • $$85.0$$
  • $$13.8$$
A zero-order reaction is one
  • in which reactants do not react
  • in which one of the reactants is in large excess
  • whose rate does not change with time
  • whose rate increases with time
A solution of $${ N }_{ 2 }{ O }_{ 5 }$$ in $$C{Cl}_{4}$$ yields by decomposition at $${45}^{o}C$$, $$4.8ml$$ of $${O}_{2}$$, $$20min$$ after the start of the experiment and $$9.6ml$$ of $${O}_{2}$$ after a very long time. The decomposition obeys first-order kinetics. What volume of $${O}_{2}$$ would have evolved, $$40min$$ after the start?
  • $$7.2ml$$
  • $$2.4ml$$
  • $$9.6ml$$
  • $$6.0ml$$
Nitric oxide, NO, and bromine vapour react together according to the following equation.
$$2NO(g)+Br_2(g)\rightarrow 2NOBr(g)$$
$$\Delta H^o=-23$$kJ$$mol^{-1}$$
The reaction has an activation energy of $$+5.4$$ kJ $$mol^{-1}$$.
What is the correct reaction pathway diagram for this reaction?
Which of the following statement is/are incorrect?
  • When $$\Delta t$$ is infinitesimally small, the average rate equals the instantaneous rate
  • Activation energy for the forward reaction equals activation energy for the reverse reaction in a catalysed reaction
  • For a reversible reaction, an increase in temperature, increase the rate for both forward and backward reaction
  • Larger the initial reactant concentration for zero-order reaction, shorter is the half-life
For what type of the following reactions is the law of mass action, never obeyed?
  • Zero order
  • First order
  • Second order
  • Third order
$$10\%$$ of a reactant decomposes in $$1$$ hour , $$20\%$$ in $$2$$ hours and $$30\%$$ in $$3$$ hours. The order of the reaction is
  • $$0$$
  • $$1$$
  • $$2$$
  • $$3$$
In a first order reaction of the type $$A(g)\rightarrow 2B(g)$$, the initial and final pressures are $$p_{1}$$ and $$p$$ respectively. The rate constant can be expressed by
  • $$k=\dfrac{1}{t}\ln \dfrac{p_{1}}{2p_{1}-p}$$
  • $$k=\dfrac{1}{t}\ln =dfrac{p_{1}}{p_{1}-p}$$
  • $$k=\dfrac{1}{t}\ln \dfrac{p_{1}}{p-p_{1}}$$
  • $$k=\dfrac{1}{t}\ln \dfrac{p_{1}}{p}$$
The half-life of $$_6C^{14}$$ if its K or $$\lambda$$ is $$ 2.31 \times 10^{-4}$$ is:
  • $$2 \times 10^2 $$ yrs
  • $$3 \times 10^3 $$ yrs
  • $$3.5 \times 10^4 $$ yrs
  • $$4 \times 10^3 $$ yrs
The rate constant for two parallel reactions were found to be $$1.0\times 10^{-2}dm^{3}$$ $$mol^{-1}s^{-1}$$ and $$3.0\times 10^{-2}dm^{3}$$ $$mol^{-1}s^{-1}$$. If the corresponding energies of activation of the parallel reactions are 60.0 KJ $$mol^{-1}$$ and 70.0 KJ $$mol^{-1}$$ respectively, then what is the apparent overall energy of activation?
  • 130.0 KJ $$mol^{-1}$$
  • 65.0 KJ $$mol^{-1}$$
  • 67.5 KJ $$mol^{-1}$$
  • 100.0 KJ $$mol^{-1}$$
Consider an endothermic reaction $$X \rightarrow Y$$ with the activation energies  $$E_{b}$$ and $$E_{f}$$ for the backward and forward reactions respectively. In general:
  • $$E_{b}> E_{f}$$
  • $$E_{b}< E_{f}$$
  • $$E_{b}=E_{f}$$
  • Any of the above
In a zero-order reaction:
  • The rate constant has the unit mol $$L^{-1}s^{-1}$$
  • The rate is independent of the concentration of the reactants.
  • The half-life depends on the concentration of the reactants.
  • The rate is independent of the temperature of the reaction.
Statement - I : Every collision of reactant molecule is not successful.
Statement - II: Every collision of reactant molecule with proper orientation is successful one.
  • Both statements are true Statement - II is correct explanation of Statement - I
  • Both statements are true but Statement -II is not correct explanation of Statement - I
  • Statement - I is true but Statement - II is false
  • Statement - I is false but Statement - II is true
During the hydrogenation of vegetable oil at $$25^{0}C$$, the pressure of  $$H_{2}$$ reduces from 2 atmospheres to 1.2 atmospheres in 50 minutes. The rate of reaction in terms of molarity per second is:
  • $$1.09\times 10^{-6}$$
  • $$1.09\times 10^{-5}$$
  • $$1.09\times 10^{-7}$$
  • $$1.09\times 10^{5}$$
For the first order gaseous reaction, $$x(g)\rightarrow 2y(g)+z(g)$$, the initial pressure, $$P_{x}=90$$ mm Hg. The pressure after 10 minutes is 180 mm Hg. The rate constant of the reaction is:
  • $$2\times 10^{-3}sec^{-1}$$
  • $$2\times 10^{3}sec^{-1}$$
  • $$1.15\times 10^{-3}sec^{-1}$$
  • $$1.15\times 10^{3}sec^{-1}$$
The gas phase decomposition of dimethyl ether follows first order kinetics:
$$CH_{3}-O-CH_{3}(g)\rightarrow CH_{4}(g)+H_{2}(g)+CO(g)$$
The reaction is carried out in a constant volume container at $$50^0 C$$ and has a half life of 14.5 minutes. Initially, only dimethyl ether is present at a pressure of 0.40 atm. What is the total pressure of the system after 12 minutes? (Assume the ideal gas behaviour.)
  • 0.946 atm
  • 0.785 atm
  • 0.777 atm
  • 0.749 atm
If the initial pressure of $$CH_{3}CHO(g)$$ is 80 mm and the total pressure at the end of 20 min is 120 mm.

                         $$CH_{3}CHO(g)\rightarrow CH_{4}(g)+CO(g)$$

What is the half-life of the first-order reaction?
  • 80 min
  • 120 min
  • 20 min
  • 40 min
Statement - I : If in a zero order reaction, the concentration of the reactant is doubled, the half-life period is also doubled.
Statement - II: For a zero order reaction, the rate of reaction is independent of initial concentration.
  • Both statements are true. Statement - II is correct explanation of Statement - I
  • Both statements are true but Statement -II is not correct explanation of Statement - I
  • Statement - I is true but Statement - II is false
  • Statement - I is false but Statement - II is true
$$75\%$$ of a first order reaction is completed in $$32$$ minutes. $$50\%$$ of the reaction will be completed in:
  • $$24$$ mins
  • $$16$$ mins
  • $$18$$ mins
  • $$23$$ mins
Which of the following graphs are correct for a zero - order reaction?
In a first order reaction, the concentration of the reactant, decreases from 0.8 M to 0.4 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M is: 
  • 30 min
  • 15 min
  • 7.5 min
  • 60 min
The total pressure after 200 seconds, if the initial pressure is $$0.1$$ atm is _______ .
  • $$0.154$$ atm
  • $$0.248$$ atm
  • $$0.174$$ atm
  • $$0.114$$ atm
The time for half-life period of a certain reaction $$\mathrm{A}\rightarrow$$ products is 1 hour. When the initial concentration of the reactant $$A$$ is 2.0 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?
  • 4 h
  • 0.5 h
  • 0.25 h
  • 1 h
For a first order reaction, (A) $$\rightarrow$$ product, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M, is:
  • $$ 1.73\displaystyle \times 10^{-5}Mmin^{-1}$$
  • $$ 3.47\displaystyle \times 10^{-4}Mmin^{-1}$$
  • $$ 3.47\displaystyle \times 10^{-5}Mmin^{-1}$$
  • $$ 1.73\displaystyle \times 10^{-4}Mmin^{-1}$$
Which of the following statement(s) is/are true for a zero order reaction?
  • $$t_{\frac{1}{2}}$$ for a zero order reaction is proportional to a, the initial concentration.
  • The rate constant is equal to the rate of the reaction at all concentrations.
  • $$t_{\frac{1}{2}}$$ is related to initial concentration of the reactant as shown in the graph.
  • The unit of rate constant is mole time$$^{-1}$$.
$$A$$ follows the first-order reaction.

 $$(A)$$  $$\longrightarrow$$ product. 

The concentration of $$A$$ changes from 0.1 $$\mathrm{M}$$ to 0.025 $$\mathrm{M}$$ in 40 minutes. Find the rate of reaction of $$A$$ when concentration of $$A$$ is 0.01 $$\mathrm{M}$$?
  • $$3.47\displaystyle \times 10^{-4}\mathrm{M}$$  $$\min^{-1}$$
  • $$3.47\displaystyle \times 10^{-5}\mathrm{M}$$ $$\min^{-1}$$
  • $$1.73\displaystyle \times 10^{-4}\mathrm{M} $$ $$\min^{-1}$$
  • $$1.73\displaystyle \times 10^{-3}\mathrm{M}$$ $$\min^{-1}$$
The time required for the decomposition of $$N_{2}O_{5}$$, so that the total pressure becomes 0.15 atm is ___________. 
(Given $$log\ 1.8=0.255$$)
  • 25.5 sec
  • 35.5 sec
  • 45.5 sec
  • 55.5 sec
$$\mathrm{l}\mathrm{n}$$ a first order reaction the concentration of reactant decreases from 800 $$\mathrm{m}\mathrm{o}l/\mathrm{d}\mathrm{m}^{3}$$ to 50 $$\mathrm{m}\mathrm{o}l/\mathrm{d}\mathrm{m}^{3}$$ is $$2\times 10^{4}$$ sec. The rate constant of reaction in $$\sec^{-1}$$ is:
  • $$2\times 10^{4}$$
  • $$3.45\times 10^{-5}$$
  • $$1.386\times 10^{-4}$$
  • $$2\times 10^{-4}$$
Select the correct statements out of I, II and III for zero order reaction.
I: Quantity of the product formed is directly proportional to time.
II: Larger the initial concentration of the reactant, greater the half-life period.
III: If 50% reaction takes place in 100 minutes, 75% reaction take place in 150 minutes.
  • I only
  • I and II only
  • II and III only
  • I, II and III
For a reaction $$P \rightarrow Q$$, the half-life of the reaction was 3h, when the initial concentration of P was 0.5M. As the concentration of P was increased to 1.0M, half life changes to 6h. The order of reaction with respect to P is:
  • zero
  • one
  • two
  • three
For the $$1^{st}$$ order reaction, $$A(g) \rightarrow 2B(g) + C(s),$$ $$t_{1/2}= 24 $$ min. The reaction is carried out by taking a certain mass of 'A' enclosed in a vessel in which it exerts a pressure of 400 mm Hg. The pressure of the reaction mixture after the expiry of 48 min will be:
  • 700 mm
  • 600 mm
  • 500 mm
  • 1000 mm
The gaseous decomposition reaction: $$A(g)\rightarrow 2B(g) + C(g)$$, is observed to first order over the excess of liquid water at $$25^oC$$. It is found that after 10 minutes, the total pressure of the system is 188 torr and after a very long time it is 388 torr. Calculate the rate constant of the reaction in $$hr^{-1}$$. The vapour pressure of $$H_2O$$ at $$25^oC$$ is 28 torr. $$[ln 2 = 0.7,\: ln 3 = 1.1, \: ln 10 = 2.3]$$
  • $$0.02$$
  • $$1.2$$
  • $$0.2$$
  • $$0.12$$
Given $$X \rightarrow$$  product (Taking $$1^{st}$$ order reaction)
conc of $$X$$
(mol/lit.)		$$0.01$$$$0.0025$$
Time (min.)$$0$$$$40$$
Half life period of this reaction is :
  • $$0\ min$$
  • $$20\ min$$
  • $$40\ min$$
  • $$\sqrt{20}\ min$$
For the reaction:

$$N_2 + 3H_2\rightarrow 2NH_3$$,

If $$\cfrac{d[NH_3]}{dt}= 2 \times 10^{-4} mol\ L^{-1}s^{-1}$$, the value of $$\cfrac{-d[H_2]}{dt}$$ would be:
  • $$1 \times 10^{-4} mol \; L^{-1}s^{-1}$$
  • $$3 \times 10^{-4} mol\; L^{-1}s^{-1}$$
  • $$4 \times 10^{-4} mol\; L^{-1}s^{-1}$$
  • $$6 \times 10^{-4} mol\; L^{-1}s^{-1}$$
The conversion of vinyl allyl ether to pent-4-enol follows first-order kinetics. The following plot is obtained for such a reaction. Determine rate constant for the reaction.

73592_cd60cf9ff0414c119714163e965d53f8.png
  • $$4.6 \times 10^{-2}s^{-1}$$
  • $$1.2 \times 10^{-2}s^{-1}$$
  • $$2.3 \times 10^{-2}s^{-1}$$
  • $$8.4 \times 10^{-2}s^{-1}$$
It takes 32 minutes to complete 99% of a first order reaction from start. Calculate the time required (in a minute) to complete 99.9% of the reaction from the start?
  • 50
  • 48
  • 55
  • 46

Half-life is independent of the concentration of the reactant. After $$10$$ minutes, the volume of $$N_{2}$$ gas is $$10\ L$$ and after complete reaction, it is $$50\ L$$. Hence, the rate constant is:

76504.jpg
  • $$(2.303 /10)\ log\ 5$$ $$min^{-1}$$
  • $$(2.303 /10)\ log\ 1.25\ min^{-1}$$
  • $$(2.303 /10)\ log\ 2\ min^{-1}$$
  • $$(2.303 /10)\ log\ 4\ min^{-1}$$
$$A(g)  \rightarrow 2B(g)+C(g)$$ is observed to be a first order reaction. On starting with pure $$A$$, it is found that, at the end of 10 min, the total pressure of the system is $$176\ mm$$ of $$Hg$$ and after a long time, it is $$270\ mm$$ of $$Hg$$. Which of the following is /are correct for the given data?
  • The initial pressure $$A$$ is $$90\ mm\ Hg$$
  • The partial pressure of $$A$$ after 10 min  is $$47\ mm\ Hg$$
  • The rate constant of the reaction is $$0.0649 /min$$
  • None of the above
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