CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 7 - MCQExams.com

For certain first-order reaction, 75% of the reaction complete in 30 min. How much time did it require to complete 99.9% of the reaction?
  • 150 min
  • 100 min
  • 90 min
  • 300 min
For the reaction system:
$$2NO(g)+O_2(g)\rightarrow 2NO_2(g)$$, volume is suddenly reduced to half its value by increasing the pressure on it. If the reaction is of first order with respect to $$O_2$$ and second order with respect to $$NO$$, the rate of reaction will:
  • diminish to one-eighth of its initial value
  • increase to eight times of its initial value
  • increase to four times of its initial value
  • diminish to one-fourth of its initial value
Which is correct about zero order reaction?
  • Rate of reaction depends on decay constant
  • Rate of reaction is independent of concentration
  • Unit of rate constant is concentration
  • Unit of rate onstant is concentration time
The rate of a particular reaction doubles when temperature change from  $${ 27 }^{ 0 }$$C to $${ 37 }^{ 0 }$$C. Calculate the energy of the activation of such reaction.
  • 53582 KJ
  • 53.58 KJ
  • 29.86 KJ
  • none of these
The activation energy of a reaction is $$94.14$$ kj/mole, and the value of rate constant at $$313$$K is $$1.8\times 10^{-1}sec^{-1}$$. Calculate the frequency factor A.
  • $$[A]=8.25\times 10^{10}s^{-4}$$.
  • $$[A]=7.923\times 10^{10}s^{-4}$$.
  • $$[A]=9.194\times 10^{10}s^{-4}$$.
  • none of these
Find the two third life $$(t_{2/3})$$ of a first order reaction in which $$K=5.48\times 10^{-14}sec^{-1}$$.
  • $$t_{2/3}=5\times 10^{13}$$ sec
  • $$t_{2/3}=2\times 10^{13}$$ sec
  • $$t_{2/3}=1.25\times10^{13}$$ sec
  • none of these
What is the activation energy of a reaction if its rate doubles when temperatures is raised from $$20^o$$C to $$35^o$$C?(R$$=8.314$$ J$$K^{-1}$$ $$mol^{-1}$$)
  • $$34.7$$ kJ $$mol^{-1}$$
  • $$15.1$$ kJ $$mol^{-1}$$
  • $$342$$ kJ $$mol^{-1}$$
  • $$269$$ kJ $$mol^{-1}$$
The rate constant for the decomposition of a hydrocarbon is $$2.418\times 10^{-5}S^{-1}$$ at $$546$$ K. If the energy of activation is $$179.9$$ kJ/mol. What will be the value of pre-exponential factor A?
  • $$[A]=9.245\times 10^{12}s^{-1}$$.
  • $$[A]=3.912\times 10^{12}s^{-1}$$.
  • $$[A]=7.83\times 10^{12}s^{-1}$$.
  • None of these
Which one of is first order reaction ?
  • $$NH_4NO_2 \rightarrow N_2 + 2H_2O$$
  • $$2HI\rightleftharpoons H_2 + I_2$$
  • $$2NO_2 \rightarrow 2NO + O_2$$
  • $$2NO + O_2 \rightarrow 2NO_2$$
The energy of activation for a first order reaction is $$104 kJ mol^{-1}$$. The rate constant at  $$25^oC$$ is $$3.7\times 10^{-5} s^{-1}$$. What is the rate constant at $$30^oC$$ ?
  • $$5.2\times 10^{-4}s^{-1}$$
  • $$7.4 \times 10^{-5} s^{-1}$$
  • $$7.72\times 10^{-5}s^{-1}$$
  • None of these
What is the activation energy for a reaction whose rate constant doubles when temperature changes from $$30^oC$$ to $$40^oC$$?
  • $$72.56\ KJmol^{-1}$$
  • $$45.45\ KJmol^{-1}$$
  •  $$54.66\ kJ mol^{-1}$$
  • None of these
Find out the percentage of the reactant molecules crossing over the activation energy barrier at 325K, given that $$\triangle { H }_{ 325 }=0.12kcal,\quad { E }_{ a(b) }=+0.02kcal$$.
  • 0.80%
  • 80.63%
  • 20%
  • None of these
For a reversible reaction : $${ N }_{ 2 }+{ O }_{ 2 }\rightleftharpoons \quad 2NO$$
Activation energy of the backward reaction is lower than that of forward reaction. The slope of k verse 1/T graph will be:
  • zero
  • $$-\frac { H }{ 2.303\quad R } $$
  • $$\frac { H }{ 2.303\quad R } $$
  • $$-\frac { \Delta H }{ \quad R }$$
Activation Energy is defined as the least possible amount of energy (minimum ) which is required to start a reaction or the amount of energy available in a chemical system for a reaction to take place.
State whether it is True or False: 
  • True
  • False
The activation energy for a certain reaction is $$334.4 kJ mol^{-1}$$. How many times larger is the rate constant at $$610$$ K than the rate constant at $$600$$ K?
  • Two times
  • Three times
  • Four times
  • None of these

 In a first-order reaction the concentration of the reactant is decreased from $$1.0{\text{ M to 0}}{\text{.25 M }}$$  in 20 min.The rate constant of the reaction would be:
  • $$10{\text{ mi}}{{\text{n}}^{ - 1}}$$
  • $$6.931{\text{ mi}}{{\text{n}}^{ - 1}}$$
  • $$0.6931{\text{ mi}}{{\text{n}}^{ - 1}}$$
  • $$0.06931{\text{ mi}}{{\text{n}}^{ - 1}}$$
A first order reaction is half-completed in $$45$$ minutes. How long does it need for $$99.9\%$$ of the reaction to be completed?
  • $$20$$ hours
  • $$10$$ hours
  • $$7\ \dfrac{3}{10}$$ hours
  • $$5$$ hours
For a first order reaction, 

$$(A)$$ $$\rightarrow$$ products, 

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:
  • $$1.73\times 10^{-4}$$ mol $$dm^{-3} min^{-1}$$
  • $$1.73\times 10^{-5}$$ mol $$dm^{-3} min^{-1}$$
  • $$3.47\times 10^{-4}$$ mol $$dm^{-3} min^{-1}$$
  • $$3.47\times 10^{-5}$$ mol $$dm^{-3} min^{-1}$$
The reaction : $$X \rightarrow$$ product, follows first-order kinetics in $$20$$ minutes, the concentration of $$X$$ changes from $$0.1 M$$ to $$0.05\ M$$ then rate of reaction when concentration of $$X$$ is $$0.02\ mol/ L$$ is:
  • $$1.73 \times 10^{-4} M/min$$
  • $$3.47 \times 10^{-5} M/min$$
  • $$6.94 \times 10^{-4} M/min$$
  • $$1.73 \times 10^{-5} M/min$$
For zero order reactions, the linear plot was obtained for $$[A]$$ vs t. The slope of the line is equal to:
  • $$k_{0}$$
  • $$-k_{0}$$
  • $$\dfrac {0.693}{K_{o}}$$
  • $$-\dfrac {K_{o}}{2.303}$$
Rate of formation of $${ SO }_{ 3 }$$ according to the reaction $$2{ SO }_{ 2 }+O_{ 2 }\rightarrow 2{ SO }_{ 3 }\quad is\quad 1.6\times { 10 }^{ -3 }kg\quad min^{ -1 }$$. Hence rate at which $$SO_{ 2 }$$ reacts is:
  • $$1.6\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$$
  • $$8.0\times { 10 }^{ -4 }kg\quad { min }^{ -1 }$$
  • $$3.2\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$$
  • $$1.28\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$$
An endothermic reaction $$A\rightarrow B$$ has an activation energy $$15kcal/mole$$ and the heat of reaction is $$5kcal/mole$$. The activation energy of reaction $$B\rightarrow A$$ is:
  • $$20kcal/mole$$
  • $$15kcal/mole$$
  • $$10kcal/mole$$
  • zero
The rate of chemical reaction is directly proportional to the equilibrium constant.
In which of the following process reaction will be completed first?
  • $$K=10$$
  • $$K=1$$
  • $$K={ 10 }^{ 3 }$$
  • $$K={ 10 }^{ -2 }$$
In a reaction involving one single reactant, the fraction of the reactant consumed may be defined as $$f=\left(1-\dfrac {C}{C_{0}}\right)$$ where $$C_{0}$$ and $$C$$ are the concentrations of the reactant at the after time, t. For a first order reaction:
  • $$\dfrac {df}{dt}=k(1-f)$$
  • $$-\dfrac {df}{dt}=kf$$
  • $$-\dfrac {df}{dt}=k(1-f)$$
  • $$\dfrac {df}{dt}=kf$$
In a first order reaction the amount of reactant decayed in three half lives (let $$a$$ be is initial amount) would be:
  • $$7a/8$$
  • $$a/8$$
  • $$a/6$$
  • $$5a/6$$
If a first order reaction is completed to the extent of $$75$$% and $$50$$% in time interval, $${t}_{1}$$ and $${t}_{2}$$, what is the ratio $${t}_{1}:{t}_{2}$$?
  • $$\ln {2}$$
  • $$\cfrac{\ln{(3/4)}}{\ln{2}}$$
  • $$2$$
  • $$1/2$$
For the consecutive unimolecular-type first order reaction $$A \xrightarrow{k_1} R \xrightarrow{k_2} S$$, the concentration of component $$R, C_R$$ at any time $$t$$ is given by $$: C_R = C_{AO} K_1 \left[\dfrac{e^{k_1t}}{(k_2 - k_1)} + \dfrac{e^{-k_2t}}{(k_1 - k_2)}\right]$$ if $$C_A = C_{AO}, CR = C_{RO} = 0$$ at $$t = 0$$ the time at which the maximum concentration of $$R$$ occurs is:
  • $$t_{max} = \dfrac{k_2 - k_1}{ln(k_2/k_1)}$$
  • $$t_{max} = \dfrac{ln(k_2/k_1)}{k_2 - k_1}$$
  • $$t_{max} = \dfrac{e^{k_2/k_1}}{k_2 - k_1}$$
  • $$t_{max} = \dfrac{e^{k_2 - k_1}}{k_2 - k_1}$$
The time for half-life period of a certain reacting $$A\rightarrow $$ product is an hour. 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?
  • 0.25h
  • 1h
  • 4h
  • 0.5h
The rate constant, the activation energy and the arrhenius parameter of a chemical reaction at $${ 25 }^{ 0 }C$$ are $$3\times { 10 }^{ 14 }{ sec }^{ -1 }:\ 104.4J{ mol }^{ -1 }$$ and $$6.0\times { 10 }^{ 14 }{ sec }^{ -1 }$$ respectively, the value of the rate constant as $$T\rightarrow \infty $$ is:
  • $$2\times { 10 }^{ 8 }{ sec }^{ -1 }$$
  • $$6\times { 10 }^{ 14 }{ sec }^{ -1 }$$
  • $$\infty$$
  • $$3.6\times { 10 }^{ 30 }{ sec }^{ -1 }$$
In the following first-order competing reactions. 

$$A+ \text{Reagent}\rightarrow \text{Product},\quad B+ \displaystyle{\text{Reagent}} \rightarrow \text{Product}$$. 

The ratio of $${ K }_{ 1 }/{ K }_{ 2 }$$ if only 50% of B will have been reacted, When 94% of A has been reacted is?
  • 4.07
  • 0.246
  • 2.06
  • 0.06
For a firt order reaction $$A\to P$$, the temperature (T) dependent rate constant (k) was found to follow the equation $$\log k = -(2000)\dfrac{1}{T}+6.0$$. The pre-exponential factor A and the activation energy $$E_a$$, respectively, are?
  • $$1.0\times 10^6s^{-1}$$ and $$9.2kJ\ mol^{-1}$$
  • $$6.0^{-1}$$ and $$16.6kJ\ mol^{-1}$$
  • $$1.0\times 10^6s^{-1}$$ and $$16.6kJ\ mol^{-1}$$
  • $$1.0\times 10^6s^{-1}$$ and $$38.3kJ\ mol^{-1}$$
 $$T (in \,K)$$ $$\dfrac{1}{T} (in \, K^{-1})$$ $$\log_{10} K$$
 $$769$$$$1.3\times 10^{-3}$$ $$2.9$$
 $$667$$ $$1.5\times 10^{-3}$$ $$1.1$$
From the following data: the activation energy for the reaction (cal/mol)  $${ H }_{ 2 }+{ I }_{ 2 }\rightarrow 2HI$$
  • $$4\times { 10 }^{ 4 }$$
  • $$2\times { 10 }^{ 4 }$$
  • $$8\times { 10 }^{ 4 }$$
  • $$3\times { 10 }^{ 4 }$$
For a reaction $$A \rightarrow B + C$$.. it was found that at the end of $$10$$ minutes from the start, the total optical rotation of the system was $$50^o$$ and when the reaction was completed a was $$100^o$$ Assuming that  "$$A$$" a optically inactive. '$$B$$' dextro rotatory and '$$C$$' is laevo rotatory rate constant of this first order reaction is ?
  • $$0.069 \,min^{-1}$$
  • $$0.69 \,min^{-1}$$
  • $$2.303 \,min^{-1}$$
  • $$4.6 \,min^{-1}$$
At $$373\ K$$, a gaseous reaction $$A\rightarrow 2B+C$$ is found to be first order. Starting with pure $$A$$, the total pressure at the end of $$10\ min$$. was $$176\ mm$$ and after a long time when $$A$$ was completely dissociated, it was $$270\ mm$$. The pressure of $$A$$ at the end of $$10$$ minutes was:
  • $$94\ mm$$
  • $$47\ mm$$
  • $$43\ mm$$
  • $$90\ mm$$
In the case of a zero-order reaction, the ratio of time required for $$75$$% completion to $$50$$ % completion is:
  • $$ln 2$$
  • $$2$$
  • $$1.5$$
  • none
Which integrated equation is correct for the following $$1^{st}$$ order reaction started with only $$A(g)$$ in a closed rigid vessel?
$$A(g)\rightarrow B(g) + C(g)+ D(g)$$

where, $$P_i= $$ initial pressure $$;\quad   P_t= $$ total pressure at time $$t $$
  • $$K=\dfrac { 2.303 }{ t } \log _{ 10 } \left[\dfrac { P_i }{P_t } \right]$$
  • $$K=\dfrac { 2.303 }{ t } \log _{ 10 } \left[\dfrac { P_t }{P_i } \right]$$
  • $$K=\dfrac { 2.303 }{ t } \log _{ 10 } \left[\dfrac { 2P_i}{3P_i-P_t} \right]$$
  • $$K=\dfrac { 2.303 }{ t } \log _{ 10 } \left[\dfrac { 3P_i}{2P_i-3P_t} \right]$$
If the concentration of reactants is reduced by n times then the value of rate constant of the first order will?
  • Increase by n times
  • Decrease by factor of n
  • Not change
  • None of these
The time elapsed of a certain between 33% and 67% completion of a first order reaction is 30 minutes. What is the time needed for 25% completion?
  • $$150.5$$ minutes
  • $$12.5$$ minutes
  • $$180.5$$ minutes
  • $$165.5$$ minutes

For which order reaction a straight line is obtained along with $$x - axis$$ by plotting a graph between half-life $$\left( {{t_{1/2}}} \right)$$ and initial concentration $$'a'$$.
  • 1
  • 2
  • 3
  • 0
For the decomposition of $$HI$$ the following logarithmic plot is shown: $$[R=1.98\ cal/mol-K]$$
The activation energy of the reaction is about?

1099536_1e30fd508e3740fb82ca5c5a32c949e6.png
  • $$45600\ cal$$
  • $$13500\ cal$$
  • $$24600\ cal$$
  • $$32300\ cal$$
How much faster would a reaction proceed at $$25^0$$C than at $$0^0$$C if the activation energy is $$65$$ kJ?
  • $$2$$ times
  • $$16$$ times
  • $$11$$ times
  • $$6$$ times
A reaction of first - order completed $$90\% $$ in $$90$$ minutes , hence , it is completed $$50\% $$ in approximately : 
  • $$ 50 min $$
  • $$ 54 min $$
  • $$ 27 min $$
  • $$ 62 min $$
Collision frequency of a gas at $$1\ atm$$ pressure is $$Z$$. Its value at $$0.5\ atm$$ will be:
  • $$0.25Z$$
  • $$2Z$$
  • $$0.50Z$$
  • $$Z$$
Collision diameter is least in case of:
  • $${ H }_{ 2 }$$
  • $$He$$
  • $${ CO }_{ 2 }$$
  • $${ N }_{ 2 }$$
The half-life of a zero-order reaction is 30 minutes. What is the concentration of the reactant left after 60 minutes?
  • $$25%$$
  • $$50%$$
  • $$6.25%$$
  • $$0$$
A certain zero order reaction has $$k = 0.025 M s^{-1}$$ for the disappearance of A. What will be the concentration of A after 15 seconds if the initial concentration is 0.50 M ? 
  • $$0.50$$ M
  • $$0.375$$ M
  • $$0.125$$ M
  • $$0.060$$ M
The rate constant for a recation is $$10.8 \times 10^{-5} mol L^{-1}S^{-1}$$. The reaction obeys:
  • First order
  • Zero order
  • Second order
  • All are wrong
If $$60\%$$ of a first order reaction was completed in $$60$$ minute, $$50\%$$ of the same reaction would be completed in approximately?
  • $$46$$ minute
  • $$60$$ minute
  • $$40$$ minute
  • $$50$$ minute
$$t_{1/2} v/s \dfrac{1}{a^2}$$ is straight line graph then determine the order of a reaction:
  • zero order
  • first order
  • second order
  • third order
For a first order reaction rate constant is given as $$\log K = 14 - \dfrac{1.2 \times 10^4}{T}$$ then what will be value of temperature if its half life period is $$6.93 \times 10^{-3}\ min$$?
  • $$100\ K$$
  • $$1000\ K$$
  • $$720\ K$$
  • $$327\ K$$
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