CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 8 - MCQExams.com

For a first - order reaction, the concentration of reactant:
  • is independent of time
  • varies linearly with time
  • varies exponentially with time
  • None

For the first order decomposition of  $${ SO }_{ 2 }{ Cl }_{ 2
} (g), { SO }_{ 2 }{ Cl }_{ 2 } \longrightarrow { SO }_{ 2 }(g) + { Cl }_{ 2 }(g)$$
A graph of $$log ({ a } -x)\ vs\ t $$ is shown in figure. What is the rate constant $$({ sec }^{ -1 })$$?


1107951_3721d6785d3442d499a5fef39e003720.png
  • 0.2
  • $$4.3   \times { 10 }^{ -5}$$
  • $$7.7  \times  { 10 }^{ -3 }$$
  • $$1.15  \times  { 10 }^{ -2 }$$

The conversion of vinyl allyl ether to pent-4-enol follows a certain kinetics. The following plot is obtained for such a reaction.
1110955_4af138dc67434591af264d3ca443b7c0.PNG
  • zero
  • -1
  • 1
  • 2
Acid hydrolysis of ester in first order reaction and rate constant is given by $$k=\dfrac { 2.303 }{ t } log\dfrac { { V }_{ \infty  }-{ V }_{ 0 } }{ { V }_{ \infty  }-{ V }_{ t } } $$ where $${ V }_{ 0 }$$,$${ V }_{ t }$$ and $$V_{ \infty  }$$ are the volume of standard $$NaOH$$ required to neutralise acid present at a given time, if ester is $$50%$$ neutralised then:
  • $${ V }_{ \infty }={ V }_{ t }$$
  • $${ V }_{ \infty }=\left( { V }_{ t }-{ V }_{ 0 } \right)$$
  • $${ V }_{ \infty }=\left( { 2V }_{ t }-{ V }_{ 0 } \right)$$
  • $${ V }_{ \infty }=\left( { 2V }_{ t }+{ V }_{ 0 } \right)$$
The reaction $${ N }_{ 2 }{ O }_{ 5 }\quad \left( In\quad { CCl }_{ 4 } \right) \rightarrow 2{ NO }_{ 2 }+{ 1 }/{ 2 }\quad { O }_{ 2 }\left( g \right) $$ is first order in $${ N }_{ 2 }{ O }_{ 5 }$$ with rate constant $$6.2\times { 10 }^{ -4 }{ S }^{ -1 }$$. What is the value of rate of reaction when $$\left[ { N }_{ 2 }{ O }_{ 5 } \right] =1.25\quad mole\quad { L }^{ -1 }$$
  • $$7.75\times { 10 }^{ -4 }\quad \quad { L }^{ -1 } { S }^{ -1 }$$
  • $$6.35\times { 10 }^{ -3 }\quad \quad { L }^{ -1 } { S }^{ -1 }$$
  • $$5.15\times { 10 }^{ -5 }\quad \quad { L }^{ -1 } { S }^{ -1 }$$
  • $$3.85\times { 10 }^{ -4 }\quad \quad { L }^{ -1 } { S }^{ -1 }$$
An endothermic reaction $$A \rightarrow B $$ have an activation energy 15 kcal/mol and the heat of reaction is 5 kcal/mol. The activation energy of the reaction  $$B \rightarrow A $$ is:
  • 20 kcal/mol
  • 15 kcal/mol
  • 10 kcal/mol
  • zero
The reaction $$ A(s) \rightarrow 2 B(g)+C(g) $$is the first order. The pressure after 20 min. and after very long time are 150 mm Hg and 225 mm Hg. The value of rate constant and pressure after 40 min. are:
  • 0.05 in 5 $$ min^{-1} $$,200mm
  • 0.5 in 2 $$ min^{-1} $$,300mm
  • 0.05 in 3 $$ min^{-1} $$,300mm
  • 0.05 in 3 $$ min^{-1} $$,200mm
In a first order reaction, the concentration of the reactant decreases from 0.8M to 0.4M in 15 min. The time taken for the concentration to change from 0.1 M to 0.025 M is:
  • 60 min
  • 15 min
  • 7.5 min
  • 30 min
Let there be as first-order reaction of the type, $$ A\rightarrow B+C $$. Let us assume that only A is gaseous. We are required to calculate the value of rate constant based on the following data.
Time0T$$ \infty $$
Partial pressure of A$$ P_{0} $$$$ P_{t} $$-
  • $$ k=\frac{1}{t}In(\frac{P_{0}}{P_{t}})$$
  • $$ k=\frac{1}{t}In(\frac{P_{t}}{P_{0}})$$
  • $$ k=\frac{1}{t}In(\frac{2P_{0}}{P_{t}})$$
  • $$ k=\frac{1}{t}In(\frac{P_{t}}{2P_{0}})$$
K for a zero order reaction is $$2\times { 10 }^{ -2 }\quad { L }^{ -1 }{ Sec }^{ -1 }$$. 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
Two identical balls A & B having velocity of 0.5 m/s & -0.3 m/s respectively. colloid elastically in 1-The velocity of A & B after collision will be?
  • -0.5 m/s, 0.3 m/s
  • -0.3 m/s,0.5 m/s
  • 0.5 m/s, 0.3 m/s
  • 0.3 m/s,0.5 m/s
$$99\%$$ of a first - order reaction was completed in $$32$$ min When will $$99.9\%$$ of the reaction complete?
  • $$50$$Min
  • $$46$$Min
  • $$49$$Min
  • $$48$$Min
$$A + B \longrightarrow C; \Delta H = + 60 KJ/mol$$
$$E_{at}$$ is $$150$$ kj. What is the activation energy for the backward reation?
  • $$210$$kJ
  • $$105$$kJ
  • $$90$$kJ
  • $$145$$kJ
The half year period for a zero order reaction is equal to:
  • $$2K/[A]o$$
  • $$\cfrac{[A]_o}{2k}$$
  • $$\cfrac{0.693}{k}$$
  • $$\cfrac{0.693}{k[A]_o}$$
What fraction of a reactant showing first order remains after 40 minute if $$t_{1/2}$$ is 20 minute?
  • 1/4
  • 1/2
  • 1/8
  • 1/6
A reaction is of first order. After $$100\ minutes\ 75\ g$$ of the reactant A are decomposed when $$100\ g$$ are taken initially. Calculate the time required  when $$150\ g$$ of the reactant A are decomposed, the initial weight taken is $$200\ g$$:
  • $$100\ minutes$$
  • $$200\ minutes$$
  • $$150\ minutes$$
  • $$175\ minutes$$
Select the correct statement regarding activation energy?
  • Activation energy may be greater than heat of reaction
  • Activation energy is less than threshold energy
  • Rate of reaction is inversely proportional to the activation energy
  • All of these
$$ 2A \rightarrow B + C $$ It would be a zero order reaction when:
  • the rate of reaction is proportional to square of conc. of A
  • the rate of reaction remains same at any conc of A
  • the rate remains unchanged at any conc. of B and C
  • the rate of reaction doubles if conc. of B is increased to double
What is the activation energy for a reaction if its rate doubles when the temperature is raised from $$20^0C$$ to $$35^0C$$? (R = 8.314 J $$mol^{-1}K^{-1}$$)
  • 269 kJ $$mol^{-1}$$
  • 34.7 kJ $$mol^{-1}$$
  • 15.1 kJ $$mol^{-1}$$
  • 342 kJ $$mol^{-1}$$
For a first order reaction involving decomposition of $$N_2O_5$$ the following information is available
$$2N_2O_5(g)\rightarrow 4NO_2(g)+O_2(g)$$ rate $$=k[N_2O_5]$$
$$N_2O_5(g)\rightarrow 2NO_2(g)+1/2 O_2(g)$$ rate $$=k^\prime[N_2O_5]$$
  • $$k=k^\prime$$
  • $$k^\prime=2k$$
  • $$k^\prime=1/2k$$
  • $$k>k^\prime$$
In a 1st order reaction the fraction of molecules at $$450^oC$$ having sufficient energy (or fraction of effective collisions) is $$1.92\times10^{-16}$$.What is activation energy value of this reaction?
  • $$27.757\times10^2 J mole^{-1}$$
  • $$21.757\times10^3 J mole^{-1}$$
  • $$21.75\times10^4 J mole^{-1}$$
  • None
For the first order consecutive reaction $$P\rightarrow Q\rightarrow R$$ under steady state approximation to $$\left[ P \right] ,\left[ Q \right]$$ and $$\left[ R \right] $$ with time are best represented by:
The rate of first order reaction, $$A \rightarrow$$ Products, is $$7.5$$ M/s. If the concentration of $$A$$ is 0.5 M. The rate constant is:
  • 3.75
  • 2.51
  •  15.0
  • 8.01
Milk turns sour at $$40^0C$$ three times as faster as at $$0^0C$$. The energy of activation for souring of milk is:
  • 4.693 kcal
  • 2.6 kcal
  • 6.6 kcal
  • none of these
A catalyst lower the energy of activation by $$25\%$$. The temperature at which rate of uncatalysed reaction would be equal to that of the catalyzed one at $$27^oC$$ is:
  • $$400^oC$$
  • $$127^oC$$
  • $$300^oC$$
  • $$227^oC$$
A $$1^{st}$$ order reaction is $$50\%$$ complete in $$30$$ minutes at $$27^oC$$ and in $$10$$ minutes at $$47^oC$$. Calculate energy of activation for the reaction.
(Assume log $$3$$=$$0.48$$)
  • $$46.87 \, KJ \, mol^{-1}$$
  • $$42.21 \, KJ \, mol^{-1}$$
  • $$44.11 \, KJ \, mol^{-1}$$
  • $$49.20 \, KJ \, mol^{-1}$$
The decomposition $$NH_3$$ gas on a heated tungsten surface gave the following results:
Initial pressure (mm)65105y185
Half-life (sec)290x670820
Calculate approximately the values of x and y.
  • x = 410 sec, y = 115 mm
  • x = 467 sec, y = 150 mm
  • x = 490 sec, y = 120 mm
  • x = 430 sec, y = 105 mm
For the zero order reaction $$A\rightarrow 2B$$, the rate constant is $$2\times 10^{-6}M min^{-1}$$ the reaction is started with 10 M of A.
  • what will be concentration of A after 2 days
  • what is intial half-line one of reaction?
  • in what time, the reaction will complete?
  • none
The time elapsed between $$33\%$$ and $$67\%$$ completion of a first order reaction is $$30$$ minutes. What is the time needed for $$25\%$$ completion?
  • $$15.5\ min$$
  • $$12.5\ min$$
  • $$18.5\ min$$
  • $$16.5\ min$$
In a particular reaction the time required to complete half of the reaction was found to increase 16 times when the initial concentration of the reactant was reduced to one-fourth. What is the order of the reaction?
  • $$1$$
  • $$4$$
  • $$2$$
  • $$3$$
Which among the following plots are liner (a-x) is the concentration of the reactant remaining after time, t? 
(1):-(a-x) vs t, for a first order reaction 
(2):- (a-x) vs t, for a zero order reaction 
(3):-(a-x) vs t, for a second order reaction 
(4):-1/ (a-x) vs t, for a second order reaction
  • 1 and 2
  • 1 and 3
  • 2 and 3
  • 2 and 4
A first order reaction follows the expression:
  • $${ C }_{ t }{ e }^{ { k }_{ 1 }t }=C_0$$
  • $$C_t={ C }_{ t }{ e }^{ { k }_{ 1 }t }$$
  • In $$\frac { { C }_{ O } }{ { C }_{ t } } =-k_1t$$
  • In $$\frac { { C }_{ t } }{ { C }_{ o } } =k_1t$$
Which of the following represents the expression for $$\cfrac{3}{4}$$th life of first order reaction?
  • $$\cfrac{2.303}{k}\log{4/3}$$
  • $$\cfrac{2.303}{k}\log{3/4}$$
  • $$\cfrac{2.303}{k}\log{4}$$
  • $$\cfrac{2.303}{k}\log3$$
The reaction $$v_1A + v_2B \rightarrow$$ products is first order with respect to $$A$$ and zero- order with respect to $$B$$.If the reaction is started with $$[A]_0$$ and $$[B]_0$$, the integrated rate expression of this reaction would be:
  • $$ln \dfrac { [A]_ 0 }{ [A]_ 0-x } =k_ 1t$$
  • $$ln\dfrac { [A]_ 0 }{ [A]_ 0-v_ 1x } =k_ 1t$$
  • $$ln\dfrac { [A]_ 0 }{ [A]_ 0-v_ 1x } =v_ 1k_ 1t$$
  • $$ln\dfrac { [A]_0 }{ [A]_ 0-v_ 1x } = -v_ 1k_ 1t$$
If a I-order reaction is completed to the extent of $$60\%$$ and $$20\%$$ in time intervals, $$t_1$$ and $$t_2$$ what is the ratio, $$t_1 : t_2$$?
  • 6.32
  • 5.587
  • 4.11
  • 8.33
What is the half life of a radioactive substance if $$75%$$ of its given amount disintegrate in $$60\ min$$?
  • $$30\ min$$
  • $$45\ min$$
  • $$75\ min$$
  • $$90\ min$$
Fora 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 is complete, it was $$ 100^o C $$ Assuming that only B and C are optically active and dextro rotatory, the rate constant of this first order reaction would be ?
  • $$ 0.069 min^{-1} $$
  • $$ 0.69 min^{-1} $$
  • $$ 6.9 min^{-1} $$
  • $$ 6.9 \times 10^{-2} min^{-1} $$
A reaction proceeds 5 times more at $${ 60 }^{ o }$$C as it does at $${ 30 }^{ o }$$C the energy of activation is $$(\log { 5=0.69990 } )$$
  • 12 K cal / mole
  • 11 K cal / mole
  • 13 K cal / mole
  • 16 K cal / mole
The rate of reaction increases with rise in temperature because of : 
  • increase in the number of activated molecules
  • increase in the activation energy
  • decrease in the activation energy
  • increase in the number of molecular collisions
A graph of $$\ln {k}$$  vs $$\left(\dfrac {1}{T}\right)$$ has slope equal to
  • $$-\dfrac {E}{2.303R}$$
  • $$+\dfrac {E_{a}}{R}$$
  • $$-\dfrac {E_{a}}{2.303R}$$
  • $$-\dfrac {E_{a}}{R}$$
$$3/4\ th$$ of first order reaction was completed in $$32\ min, 15/16$$ the part will be completed in ?
  • $$24\ min$$
  • $$64\ min$$
  • $$16\ min$$
  • $$32\ min$$
When ln k is plotted against $${ 1 }/{ T }$$, the slope was found to be -10.7 $$\times $$ $${ 10 }^{ 3 }$$ K, activation energy for the reaction would be :
  • -78.9 kJ $${ mol }^{ -1 }$$
  • 2.26 kJ $${ mol }^{ -1 }$$
  • 88.9 kJ $${ mol }^{ -1 }$$
  • 10.7 kJ $${ mol }^{ -1 }$$
The decomposition of $$NH_3$$ on platinum surface is zero order reaction. What are the rates of production of $$N_2$$ and $$H_2$$ if $$K= 2.5\times 10^{-4} mol^{-1} L s^{-1}$$?
  • $$2.5 \times 10^{-4}$$ and $$7.5 \times 10^{-4}$$ respectively
  • $$1.25 \times 10^{-4}$$ and $$3.75 \times 10^{-4}$$ respectively
  • $$3.75 \times 10^{-3}$$ and $$1.25 \times 10^{-3}$$ respectively
  • $$1.25 \times 10^{-3}$$ and $$3.25 \times 10^{-3}$$ respectively
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
The rate of a reaction at 200 K 100 times less than the rate at 400 K.The activation energy of the reaction is 
  • 184 R
  • 1840 R
  • 460 R
  • 4600 R
Rate constant of a first order reaction is $$1.15\times 10^{-5}$$. The percentage of initial concentration that remained after 1 hour is?
  • $$89.15\%$$
  • $$95.96\%$$
  • $$55.86\%$$
  • $$83.45\%$$
The activation energy for the bimolecular reaction $$A+BC \rightarrow AB+C$$ is $$E_{0}$$ in the gas phase. If the reason carried out in a confined volume of $$\lambda^{3}$$, the activation energy is expected to: 
  • remain unchanged
  • increase with decreasing $$\lambda$$.
  • decrease with decreasing $$\lambda$$.
  • oscillate with decreasing $$\lambda$$.
Radioactive decay follows                   order kinetics
  • 0
  • 1
  • 2
  • 3
In a first order reaction ,if $$25\%$$ of the reaction is completed in $$50$$ minutes $$50\%$$ of the total reaction is completed in _________ minutes (approx):
  • $$120$$
  • $$100$$
  • $$80$$
  • $$150$$
For a first order reaction, the plot of $$'t'$$ against $$log C$$ gives a straight line with slope equal to:
  • $$(k/2.2303)$$
  • $$(-k/2.303)$$
  • $$(In k/2.303)$$
  • $$-k$$
0:0:1


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