CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 13 - MCQExams.com

A reaction requires 60 minutes and 20 minutes to complete 50% at $$27^o C$$ and $$47^oC$$ respectively. calculate activation energy of the reaction.
  • $$45678$$ cal
  • $$26789$$ cal
  • $$10480$$ cal
  • None of these
What will be the initial rate of a reaction if its rate constant is $${10}^{-3}{min}^{-1}$$ and the concentration of reactant is $$0.2\ mol .{dm}^{-1}$$. Also, the amount of reactant converted into products in 200 minutes is:
  • $$2\times{10}^{-4} mol. {dm}^{-3}{min}^{-1}$$, $$81.97\%$$
  • $$2\times{10}^{-4} mol. {dm}^{-3}{min}^{-1}$$, $$18.03\%$$
  • $$2\times{10}^{-4} mol. {dm}^{-3}{min}^{-1}$$, $$76\%$$
  • $$2\times{10}^{-4} mol. {dm}^{-3}{min}^{-1}$$, $$24\%$$
$$75\%$$ of a first-order reaction is completed in 30 minutes. What is the time required for $$93.75\%$$ of the reaction (in minutes) ?
  • $$45$$
  • $$120$$
  • $$90$$
  • $$60$$
When the initial concentration of the reactant doubled, the half-life period of the reaction is also doubled. Hence the order of the reaction is
  • one
  • two
  • fraction
  • zero
A reaction  $$P \rightarrow Q$$  is  $$25\%$$  complete in  $$25 min,$$   $$50\%$$  complete in  $$25 min$$  if  $$[ P ]$$  is halved. The reaction is  $$25 \%$$  completed in   $$50 min$$  if  $$[ P ]$$  is doubled. The order of reaction is
  • $$1$$
  • $$2$$
  • $$0$$
  • $$3$$
The initial concentration of $$N_2O_5$$ in the following first order reaction  $$N_2O_{5(g)} \rightarrow 2NO_2(g) + \dfrac{1}{2} O_2 (g)$$ was $$1.24 \times 10^{-2} \ molL^{-1}$$ at 318 K. The concentration of $$N_2O_5$$ after 60 min was $$0.20 \times 10^{-2} \ molL^{-1}$$. Calculate the rate constant of the reaction at 318 K.
  • $$0.0104 min^{-1}$$
  • $$0.0204 min^{-1}$$
  • $$0.0304 min^{-1}$$
  • $$0.0404 min^{-1}$$
Reaction $$A\rightarrow B$$ follows second order kinetics. Doubling the concentration of A will increase the rate of formation of B by a factor of:
  • $$1/4$$
  • $$1/2$$
  • $$2$$
  • $$4$$
The half-life of a first-order reaction is 10 min. If the initial amount is 0.08 mol/L and the concentration at some instant is 0.01mol/L then time will be:
  • 10 min
  • 30 min
  • 20 min
  • 40 min
Consider the following first order competing reaction :
$$X\xrightarrow{{{K_1}}}A + B$$ and $$Y\xrightarrow{{{K_2}}}C + D$$ 
if $$50\% $$ of the reaction of $$X$$ was completed when $$96\% $$ of the reaction of $$Y$$ was completed , the ratio of their rate constant $$\left( {{K_2}/{K_1}} \right)$$ is:
  • $$4.06$$
  • $$0.215$$
  • $$1.1$$
  • $$4.65$$
The curves $$M$$ and $$N$$ represent the variation of energy with reaction coordinates for the reaction $$A(g)+B(g) \rightleftharpoons  C(g)+D(g)$$ in absence and presence of negative catalyst
Of the curves $$M$$ and $$N$$, which represents the $$E_{a}$$ for the backward reaction in the presence of catalyst 
1286328_f1e31d0ed60f4b9f82ecf6d0160731e4.png
  • $$P$$
  • $$Q$$
  • $$S+P$$
  • $$P+Q$$
In a first order reaction, $$0.16$$ moles of reactant decrease to $$0.02$$ moles in $$144$$ minutes, its half life is ?
  • $$24$$
  • $$12$$
  • $$72$$
  • $$48$$
For a zero order reaction:
  • $${ t }_{ \frac { 1 }{ 2 } }\propto a$$
  • $${ t }_{ \frac { 1 }{ 2 } }\propto \cfrac { 1 }{ a } $$
  • $${ t }_{ \frac { 1 }{ 2 } }\propto { a }^{ 2 }$$
  • $${ t }_{ \frac { 1 }{ 2 } }\propto \cfrac { 1 }{ { a }^{ 2 } } $$
A graph of $$log_{10}k$$ is plotted against $$1/T$$ for a reaction with order 2.If the activation energy is 10 kJ/mol, then magnitude of the slope will be: 
  • $$4.34\times 10^3$$
  • $$5.2\times 10^2$$
  • $$1.2\times 10^4$$
  • $$6.8\times 10^{-3}$$
In a zero order reaction 47.5% of the reactant remains at the end of 2.5 hours. The amount of reactant consumed in one hour is 
  • 10.5%
  • 32.0%
  • 52.6%
  • 21.0%
The decomposition of A follows first order kinetics by the following equation:

$$4A (g) \xrightarrow{\Delta} B(g) + 2C(g)$$

If initially, the total pressure was $$800$$ mm of Hg and after $$10$$ minutes it is found to be $$650$$ mm of Hg. What is the half-life of A?
(Assume only A is present initially)
  • $$10$$ minutes
  • $$5$$ minutes
  • $$7.5$$ minutes
  • None of these
For a reaction
$$2A+B\rightarrow C+D$$, the active mass of $$B$$ is kept constant but that of $$A$$ is tripled. The rate of reaction will -
  • Decrease by $$3$$ times
  • Increased by $$9$$ times
  • Increase by $$3$$ times
  • Unpredictable
For a reaction: nA→→ product, the rate constant and rate of reactions are equal, What is the order of the reaction ?
  • 0
  • 1
  • 2
  • 3
The time taken for the completion of 90% of a first order reaction is 't' min. What is the time (in sec) taken for the completion of 99% of the reaction ?
  • $$2t$$
  • $$t/30$$
  • $$120t$$
  • $$60t$$
For zero  order reaction, A$$ \to $$,a graph of rate vs time has slope equal to:( where k$$=$$rate of reaction)
  • k
  • -k
  • zero
  • -2.303 k
For a homogeneous reaction $$A\rightarrow 3B$$, if pressure after sometime $$t$$ was $$P_t$$ and after completion of reaction, pressure was $$P_\infty $$.Then select the correct relation.
  • $$K \times t $$ = ln $$(\cfrac { 2P_\infty }{ 3(P_\infty -Pt) } )$$
  • $$K \times t$$ = ln $$(\cfrac {7 P_\infty }{ 3(P_\infty -Pt) } )$$
  • $$K \times t$$ = ln $$(\cfrac {3P_\infty }{ 2(P_\infty -Pt) } )$$
  • $$K \times t$$ = ln $$(\cfrac {5P_\infty }{ 2(P_\infty -Pt) } )$$
The general integrated rate equation for first-order reaction is given by:
  • $$k=\cfrac{2.303}{t}ln\cfrac{[A]_{0}}{[A]_{t}}$$
  • $$k=\cfrac{1}{t}ln\cfrac{[A]_{0}}{[A]_{t}}$$
  • $$k=\cfrac{2.303}{t}log_{10}\cfrac{[A]_{0}}{[A]_{t}}$$
  • $$k=\cfrac{1}{t}ln\cfrac{[A]_{0}}{[A]_{t}}$$
The first order reaction has half-life of $$18$$ hrs. What percentage of the reactant will remain after $$24$$hrs  $$\left( {\log 2 = 0.3,\log 2.5 = 0.4} \right)$$
  • $$20\% $$
  • $$40\% $$
  • $$45.5\% $$
  • $$68.2\% $$
The rates of most reactions doubled when their temperature is raised from $$298\ K$$ to $$308\ K$$, calculate their activation energy?
  • $$42.0\ kJ$$
  • $$5.29\ kJ$$
  • $$4.2\ kJ$$
  • $$52.9\ kJ$$
A first order reaction goes upto 8% in 10 min. What time will it take to complete 99%
  • 555.55min
  • 305.52 min
  • 158.32 min
  • 155.55 min
The rate constant of a reaction increased by $$5%$$ when temperature is raised from $$27^{o}$$ to $$28^{o}\ C$$. The activation energy of the reaction is $$(\log\ 7=0.8450)$$
  • $$36.5\ KJ$$
  • $$16.5\ KJ$$
  • $$47.5\ KJ$$
  • $$27.5\ KJ$$
The catalysts decrease the Ea from $$100 KJmol^-1$$ to $$80 KJmol^-1$$. At what temperature the rate of reaction in the absence of catalyst at 500 K will be equal to the rate of reaction in the presence of a catalyst .
  • $$400K$$
  • $$625K$$
  • $$-1000K$$
  • $$+1000K$$
At least how half-lives should elapse for a I order reaction $$A\rightarrow$$ products so that the reaction is at least $$95%$$ completed ? $$(\log 2=0.3)$$
  • $$6$$
  • $$5$$
  • $$4$$
  • $$7$$
The reaction, $$X \rightarrow Y$$ is an exothermic reaction. Activation energy of the reaction for conversation of $$x$$ into $$Y$$ is $$150kJ mol^{-1}$$. Enthalpy is $$135 kJ mol^{-1}$$. The activation energy for the reverse reaction, $$Y \rightarrow X$$ will be
  • $$280 kJ mol^{-1}$$
  • $$285 kJ mol^{-1}$$
  • $$270 kJ mol^{-1}$$
  • $$15kJ mol^{-1}$$
The rate constant of the first-order reaction may be described by following equation:

log K = $$ 14.34 - \cfrac{1.25 \times 10^4}{T} $$, calculate energy of activation.
  • 239.34kJ
  • 239.34 kcal
  • 239.34J
  • 239.34 cal.
Which one of the following plots is correct for a first order reaction:
If the concentration of reactant is reduced by n times, then the value of rate constant of the first order will 
  • Increase by n times
  • Decrease by n times
  • Not change 
  • Increase by 2n times
The initial concentration of cane sugar in presence of an acid was reduced from $$0.20$$ to $$0.10\ M$$ in $$5$$ hours and to $$0.05\ M$$ in $$10$$ hours, what is the value of $$K$$? $$(in\  hr^{-1})$$
  • $$0.0693$$
  • $$1.386$$
  • $$0.1386$$
  • $$3.465$$
For a first order reaction, the ratio of time for the completion of 99.9% and half of the reaction is
  • $$8$$
  • $$2$$
  • $$6.6$$
  • $$10$$
 If a reaction follows the Arrhenius equation, the plot $$lnK$$ vs $$ \dfrac{1}{(RT)}$$  gives a straight line with a gradient $$(-y)$$ unit. The energy required to activate the reactant is : 
  • y unit
  • -y unit
  • yR unit
  • y/R unit

The concentration of $$N_{2}O_{5}$$ in liquid bromine varied with time as follows:


$$t/s$$

$$0$$

$$100$$

$$300$$

$$500$$

$$[N_{2}O_{5}]M$$

$$0.12$$

$$0.088$$

$$0.049$$

$$0.026$$

What will be the rate constant and order of reaction?
  • $$k=2\times 10^{-3}s^{-1}$$, order$$=1st$$
  • $$k=3.06\times 10^{-3}s^{-1}$$, zero
  • $$k=4\times 10^{-3}s^{-1}$$, zero
  • None of these
The rate  law of the reaction A + 2B $$\rightarrow $$ product is given by $$\frac{d(product)}{dt} = k[A]^2[B]$$. If $$A$$ is taken in large excess, the order of the reaction will be:
  • 1
  • 2
  • 3
  • 0
Consider the following in respect of zero-order reaction
i. $${ t }_{\frac{1}{2} }$$ is directly proportional to the initial concentration
ii. Time taken for the completion of the reaction is twice its $${ t }_{ 1/2 }$$
iii. Concentration of the reactant decreases linearly with time
Which of the statements given above are correct?
  • I&II only
  • I&III only
  • II & III only
  • I, II & III
Activation energy of forward and backward process of reaction are 60 kJ and 40 $$kJ \ mol^{-1}$$ respectively . Which of the following are true statements ?
  • It is endothermic reaction.
  • It is exothermic reaction.
  • Heat of reaction is $$+20\ kJ \ mol^{−1}$$
  • Thershold enregy of reaction is $$100 \ kJ\,mo{l^{ - 1}}$$
If the values of enthalpies of reactants and products are p and q J/mol respectively. If the activation energy for the backward reaction is r J/mol, then the activation energy for forward reaction will be in (J/mol) (take only magnitudes)
  • p-q-r
  • p-q+r
  • q-p-r
  • q-p+r
Activation energy of the backward reaction is 10 kcal and $$\Delta H=$$ 2.813 kcal.

Activation energy of the forward reaction is ___________ kcal.
  • $$128.13$$
  • $$12.813$$
  • $$12813$$
  • none of these
Decomposition of HI (g) on Gold surface is zero order reaction.Initially few moles of $$H_2$$ are present in container then which of the following graph is correct?
For the decomposition of $${ N }_{ 2 }{ O }_{ 5 }(g)$$ it is given that - $${ 2N }_{ 2 }{ O }_{ 5 }(g)\longrightarrow 4{ NO }_{ 2 }(g)$$ Activation energy = Ea, $${ N }_{ 2 }{ O }_{ 5 }(g)\longrightarrow { 2NO }_{ 2(g) }+\frac { 1 }{ 2 } { O }_{ 2 }(g)$$ activation energy =$${ E }a^{ ' }$$then 
  • $$Ea=2{ E }a$$
  • $$Ea>{ E }a^{ ' }$$
  • $$Ea<{ E }a^{ ' }$$
  • $$Ea={ E }a^{ ' }$$
For a particular gaseous reaction a graph was plotted as shown. It shows that the reaction of $$A$$ is
1386948_e50d9dd12d744070a54c2afdc4076584.PNG
  • Zero order w.r.t $$A$$
  • 1st order w.r.t $$A$$
  • Second order w.r.t $$A$$
  • a non-integer order w.r.t $$A$$
For a first order reaction, $${\text{A}} \to {\text{P,}}{{\text{t}}_{{\text{1/2}}}}\left( {{\text{half -}}\,{\text{life}}} \right)$$  is $$10$$ days. The time required for $$\dfrac{1}{4}^{th}$$ conversion of $$A$$(in days) is : $$\left( {{\text{ln}}\,{\text{2 = 0}}{\text{.693,  ln}}\,{\text{3 = 1}}{\text{.1}}} \right)$$
  • $$4.1$$
  • $$5$$
  • $$2.5$$
  • $$3.2$$
For the chemical reaction, $$A \to $$ products, the following $$\log \,K = 16.398 - \cfrac{{2800}}{T}$$
Arrhenius factor for the reaction is______________
  • $$2.5 \times {10^{16}}$$
  • $$5 \times {10^{16}}$$
  • $$10^9$$
  • None of these 
According to the Arrhenius equation, 
  • a high activation energy usually implies a fast reaction
  • rate constant increases with increase in temperature. This is due to a greater number of collisions whose energy exceeds the activation energy
  • higher the magnitude of activation energy, stronger is the temperature dependence of the rate constant.
  • the pre-exponential factor is a measure of the rate at which collisions occure, irrespective of their energy.
For a gaseous equilibrium : $$2A(g)\rightleftharpoons 2B(g)+C(g)$$  $$K_{p}$$  has a value 1.8 at 700 K.  The value of $$K_{c}$$  for the equilibrium : $$2B(g+C(g)\rightleftharpoons 2A(g)$$  at that temperature is about  _________.
  • 0.031
  • 32
  • 57.4
  • 103.3
In the following first order competing reaction:
A+Reagent $$\longrightarrow$$ Product B+Reagent $$\longrightarrow$$ Product
The ratio of $${ K }_{ 1 }/{ K }_{ 2 }$$ if only 50% of B will have been reacted when 94% of A has been reacted is:
  • 4.06
  • 0.246
  • 2.06
  • 0.06
$$A\rightarrow B$$ first order reaction $$A$$ is optical active and $$B$$ is optically inactive, a series of experiment were conducted on a solution of $$A$$
Time060 min$$\infty$$
optical rotation$${82}^{o}$$$${77}^{o}$$$${2}^{o}$$
Assume some impurity present calculate the optical rotation after $$5$$ hours
(Given in $$1.066=0.064,{e}^{0.16}=1.17$$)
  • 60
  • 30
  • 20
  • 120
For an exothermic reaction $$Ea, Ea^{'} $$ are the activation energies of the forward and backward reactions respectively. Then which is always false:
  • $$E_{a} < {E_a}^{'}$$
  • $$E_{a} > \triangle H$$
  • $$E_{a} < \triangle H$$
  • $${E_a}^{'} < \triangle H$$
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