CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 11 - MCQExams.com

The decomposition of $$Cl_2O_7$$ at 400 K in gaseous phase to $$Cl_2$$ and $$O_2$$ is 1st order reaction. After 55 sec at 400 K, the pressure of reaction mixture increases from 0.62 to 1.88 atm. Calculate the rate constant of the reaction. Also, calculate the pressure of reaction mixture after 100 seconds:
  • $$1.58\times 10^{-2}, 2.33 atm$$
  • $$1.58\times 10^{-3}, 2.33 atm$$
  • $$15.8\times 10^{-2}, 23.3 atm$$
  • None of these
In the thermal decomposition of $$N_2O$$ at 830 K, the time required to decompose half of the reactant was 263 sec at the initial pressure 290 mm. It takes 212 sec to decompose half of the reactant if initial pressure was 360 mm. What is the order of the reaction? Also calculate $$t_{1/2}$$ for $$N_2O$$ decomposition if initial pressure of $$N_2O$$ is 1 atm.
  • $$O.R=2 $$, Half life $$=100.2 sec $$
  • $$O.R=1 $$, Half life $$=10.02 sec $$
  • $$O.R=4 $$, Half life $$=1.002 sec $$
  • None of these
A substance reacts according to 1$$^{st}$$ order kinetic and rate constant for the reaction is $$1\times 10^{-2} sec^{-1}$$. If the initial concentration is 1 M. Rate of the reaction after 1 minute is:
  • $$5.49\times 10^{-3} mol\ litre^{-1} sec^{-1}$$
  • $$5.55\times 10^{-3} mol\ litre^{-1} sec^{-1}$$
  • $$7.49\times 10^{-3} mol\ litre^{-1} sec^{-1}$$
  • None of these
Mathematical expression for $$t_{1/4}$$ i.e., when $$(1/4)^{th}$$ reaction is over following first order kinetics can be given by:
  • $$t_{1/4}=\frac {2.303}{K}log 4$$
  • $$t_{1/4}=\frac {2.303}{K}log 1/4$$
  • $$t_{1/4}=\frac {2.303}{K}log 2$$
  • $$t_{1/4}=\frac {2.303}{K}log \frac {4}{3}$$
Catalytic decomposition of nitrous oxide by gold at $$900^oC$$ at an initial pressure of $$200$$ mm, was $$50$$% in $$53$$ minutes and $$73$$% in $$100$$ minutes.
Velocity constant of the reaction is:
[Note: assume decomposition as the first order.]
  • $$1.308\times 10^{-2}$$
  • $$2.317\times 10^{-2}$$
  • $$3.208\times 10^{-3}$$
  • none of these
According to the collision theory, most molecular collisions do not lead to a reaction. Which of the following is(are) necessary for collisions to successfully lead to the reaction?
  • The total kinetic energy of the collision must be greater than some minimum value.
  • A catalyst must be present at the collision.
  • The colliding particles must be properly oriented in space when they collide.
  • None of the above.
A 1st order reaction is 50% complete in 30 minute at $$27^oC$$ and in 10 minute at $$47^oC$$. The sum of rate constants for reaction at $$27^oC$$ and $$47^oC$$ is:
  • $$9.24\times 10^{-2} min^{-1}$$
  • $$12.24\times 10^{-2} min^{-1}$$
  • $$8.24\times 10^{-2} min^{-1}$$
  • None of these
Reaction $$A+B\longrightarrow C+D$$ follow's following rate law rate $$=k={ \left[ A \right]  }^{ \frac { 1 }{ 2 }  }{ \left[ B \right]  }^{ \frac { 1 }{ 2 }  }$$. Starting with initial conc. of one mole of A and B each, what is the time taken for amount  of A of become 0.25 mole. Given $$k = 2.31\times 10^{-3}  sec^{-1}$$.
  • 300 sec
  • 600 sec
  • 900 sec
  • none of these
The gas phase decomposition of dimethyl ether follows first order kinetics.
$$CH_3OCH_3(g)\, \rightarrow\, CH_4(g)\, +\, H_2(g)\, +\, CO(g)$$
The reaction is carried out in a constant volume container at $$500^\circ C$$ and has a half life of 14.5 min. Initially, only dimethyl ether is present at a pressure of 0.40 atm. What is the total pressure of the system after 12 min? Assume ideal gas behaviour.
  • 0.74 atm
  • 7.4 atm
  • 74 atm
  • none
Catalytic decomposition of nitrous oxide by gold at $$900^{0}C$$ at an initial pressure of 200 mm was 50 % in 53 min and 73 % in 100 min, the value of velocity constant is :
  • $$1.308 \, \times\, 10^{-2}\, min^{-1}$$
  • $$1.432 \, \times\, 10^{-2}\, min^{-1}$$
  • $$2.318 \, \times\, 10^{-2}\, min^{-1}$$
  • None of these 
A first-order reaction: A $$\rightarrow$$ Products and a second order reaction: 2R $$\rightarrow$$ Products both have a half time of 20 min when they are carried out taking 4 mol $$L^{-1}$$ of their respective reactants. The number of a mole per litre of A and R remaining unreached after 60 min from the start of the reaction, respectively, will be:
  • 1 and 0.5 M
  • 0.5 M and negligible
  • 0.5 and 1 M
  • 1 and 0.25 M
In a first order reaction, $$75\%$$ of the reactants disappeared in 1.386 hr. What is the rate constant?
  • $$3.6\, \times\, 10^{-3}\, s^{-1}$$
  • $$2.7\, \times\, 10^{-4}\, s^{-1}$$
  • $$72\, \times\, 10^{-3}\, s^{-1}$$
  • $$1.8\, \times\, 10^{-3}\, s^{-1}$$
Which of the following isomerization reactions is/are of the first order ?
  • Cyclopropane $$\rightarrow$$ Propane
  • cis-But-2-ene $$\rightarrow$$ Trans-but-2-ene
  • Vinyl allyl ether $$\rightarrow$$ Pent-4-enal
  • $$CH_4NC\, \rightarrow\, CH_3CN$$
$$A\rightleftharpoons B+C$$
Time              $$  t$$        $$\infty $$
Total pressure of $$(B + C)$$    $$P_2$$        $$P_3$$
Find equilibrium constant $$k$$.
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{3}}{2(P_{3}-P_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{2}}{2(P_{3}-P_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{3}}{2(P_{3}+P_{2})}$$
  • None of these
$$A \rightarrow Product, [A]_{0} = 2M$$. After $$10\ min$$ reaction is $$10\%$$ completed. If $$\dfrac {d[A]}{dt} = k[A]$$, then $$t_{1/2}$$ is approximately.
  • $$0.693 min$$
  • $$69.3 min$$
  • $$66.0 min$$
  • $$0.0693 min$$
80% of a first order reaction was completed in 70 min. How much it will take for 90% completion of a reaction ?
  • 114 min
  • 100 min
  • 140 min
  • 70 min
In a first order reaction, the initial conc. of the reactant was $$M/10.$$ After 8 minutes 20 seconds the conc. becomes $$\,M/100.\,$$
What is the rate constant?
  • $$\;5\times10^{-3}\,second^{-1}$$
  • $$\;2.303\times10^{-5}\,second^{-1}$$
  • $$\;2.303\times10^{-4}\,second^{-1}$$
  • $$\;4.606\times10^{-3}\,second^{-1}$$
The decomposition of a compound P, at temperature T according to the equation 
$$2P_{(g)}\rightarrow4Q_{(g)}+R_{(g)}+S_{(l)}$$ is the first order reaction. After 30 minutes from the start of decomposition in a closed vessel, the total pressure developed is found to be 317 mm Hg and after a long period of time the total pressure observed to be 617 mm Hg. Calculate the total pressure of the vessel after 75 minute, if volume of liquid S is supposed to be negligible. Also calculate the time fraction $$t_{7/8}$$?
Given : Vapour pressure of S(l) at temperature T = 32.5 mm Hg.
  • $$P_{t}=37.955\:mm\:Hg,\:t_{7/8}=39.996\:min$$
  • $$P_{t}=379.55\:mm\:Hg,\:t_{7/8}=399.96\:min$$
  • $$P_{t}=179.55\:mm\:Hg,\:t_{7/8}=199.96\:min$$
  • None of these
$$60$$% of the first-order reaction was completed in $$60$$ min. The time taken for reactants to decompose to half of their original amount will be:
  • $$\approx\, 30\, min$$
  • $$\approx\, 60\, min$$
  • $$\approx\, 90\, min$$
  • $$\approx\, 45\, min$$
A vessel contains dimethyl ether at a pressure of 0.4 atm. Dimethyl ether decomposes as $$CH_{3}OCH_{3}(g)\rightarrow CH_{4}(g)+CO(g)+H_{2}(g)$$. The rate constant of decomposition is $$4.78\times10^{-3}\:min^{-1}$$. Calculate the ratio to initial rate of diffusion of rate of diffusion after 4.5 hour of initiation of decomposition. Assume the composition of gas present and composition of gas diffusing to be same.
  • $$0.26 : 1$$
  • $$0.13 : 1$$
  • $$1: 0.26$$
  • $$1 : 0.13$$
In this case we have
                       $$A\rightarrow  B+C$$
Time              t           $$\infty $$
Total $$press^{r}$$   $$P_2$$        $$P_3$$
Find k?
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{3}}{2(P_{3}-P_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{3}}{2(P_{3}+P_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{2}}{2(P_{3}-P_{2})}$$
  • $$\displaystyle k=\frac{1}{t}ln\frac{P_{2}}{2(P_{3}+P_{2})}$$
In the following reaction, $$A\rightarrow B$$, rate constant is $$1.2\times10^{-2}\:M\:s^{-1}\:$$. What is concentration of B after 10 min, if we start with 10 M of A?
  • 7.2 M
  • 14.4 M
  • 3.6 M
  • None of these
90% of a first order reaction was completed in 100 min. What is the half life of the reaction ?
  • 63.3 min
  • 53.3 min
  • 43.3 min
  • 30 min
In a certain reaction, 10% of the reactant decomposes in one hour, 20% in two hours, 30% in three hours, and so on. The dimension of the velocity constant (rate constant) is:
  • $$Hr^{-1}$$
  • $$Mol\, L^{-1}\, hr^{-1}$$
  • $$L\, mol^{-1}\, s^{-1}$$
  • $$Mol\, s^{-1}$$
In a first order reaction, the initial concentrated of the reactant was $$M/10.$$ After $$8$$ minutes $$20$$ seconds the concentrated becomes $$\,M/100.\,$$. What is the rate constant?
  • $$\;5\times10^{-3}\,sec^{-1}$$
  • $$\;2.303\times10^{-5}\,sec^{-1}$$
  • $$\;2.303\times10^{-4}\,sec^{-1}$$
  • $$\;4.606\times10^{-3}\,sec^{-1}$$
Unit of frequency factor (A) is:
  • mol/L
  • mol/L.s
  • depend upon order of reaction
  • it does not have any unit
For a first-order reaction, the concentration changes from $$0.8\ M$$ to $$0.4\ M$$ in $$15$$ mins. The time taken for the concentration to change from $$0.1\ M$$ to $$0.025\ M$$ is:
  • $$30$$ mins.
  • $$15$$ mins.
  • $$7.5$$ mins.
  • $$60$$ mins.
The rate constant of the reaction $$A\rightarrow B$$ is $$0.6\times 10^{-3} \ moleL^{-1}s^{-1}$$. If the concentration of $$A$$ is $$5 \ M$$, then concentration of $$B$$ after $$20 \ minutes$$ is:
  • $$0.36 M$$
  • $$0.72 M$$
  • $$1.08 M$$
  • $$3.60 M$$
_________ increases effective collisions without increasing average energy.
  • An increase in the reactant concentration
  • An increase in the temperature
  • A decrease in pressure
  • Catalysts
  • $$\displaystyle pH$$
What is the activation energy of the reverse reaction by this diagram?

480953.JPG
  • $$E$$
  • $$D$$
  • $$C$$
  • $$B$$
Which of the following choice is correct regarding to increase the rate of a reaction?
  • Decreasing the temperature
  • Increasing the volume of the reaction vessel
  • Reducing the activation energy
  • Decreasing the concentration of the reactant in the reaction vessel
Which statements describe the condition(s) required for a successful formation of a product in a reaction ?
  • The collision must involve a sufficient amount of energy, provided from the motion of the particles, to overcome the activation energy
  • The relative orientation of the particles has little or no effect on the formation of the product
  • The relative orientation of the particles has an effect only if the kinetic energy of the particles is below some minimum value
  • The relative orientation of the particles must allow for formation of the new bonds in the product
  • The energy of the incoming particles must be above a certain minimum value and the relative orientation of the particles must allow for formation of new bonds in the product
If $$50$$% of the reactant is converted into a product in a first order reaction in 25 minutes, how much of it would react in 100 minutes?
  • $$93.75$$%
  • $$87.5$$%
  • $$75$$%
  • $$100$$%
Why does the probability curve become narrower when gas particles are more massive?
  • The gas particles can travel at higher speeds
  • The gas particles are less likely to travel at slower speeds
  • The gas particles are more likely to travel at higher speeds
  • The gas particles can not travel at higher speeds
  • There are more collisions between gas particles
Consider the three statements about reaction energy diagrams and the relative magnitudes of the activation energy, $$E_{a}$$, and the enthalpy of reaction, $$\Delta H$$.
One or more of the statements is true.
Identify the correct statement or combination of statements from the four choices below.
Statement
IFor an endothermic reaction, the magnitude of $$E_{a}$$ is always greater than $$\triangle H$$.
IIFor an exothermic reaction, the magnitude of $$E_{a}$$ is always greater than $$\triangle H$$.
IIIFor an exothermic reaction, adding a catalyst will decrease the magnitude of $$\triangle H$$.
  • Statement I only is true.
  • Statement II only is true.
  • Both statements I and II are true.
  • Both statements I and III are true.
Among the following which will decrease the rate of the reaction?
i. Using highly concentrated reactants
ii. Decreasing the temperature by $$25\ K$$
iii. Stirring the reactants
  • i only
  • ii only
  • i and iii only
  • ii and iii only
  • i, ii, and iii
The rate of reaction increases with rise in temperature because of :
  • Increase in number of activated molecules
  • Increase in energy of activation
  • Decrease in energy of activation
  • Increase in the number of effective collisions
$$2N_2O_5(g) \rightarrow 4NO_2(g) + O_2(g)$$
What is the ratio of the rate of decomposition of $$N_2O_5$$ to rate of formation of $$NO_2$$?
  • 1 : 2
  • 2 : 1
  • 1 : 4
  • 4 : 1
What does it mean when a collision is elastic?
  • No energy is gained or lost.
  • Energy is gained.
  • Energy is lost.
  • The particles can stretch out.
  • The particles slow down.
Consider the Arrhenius equation, $$k = Ae^{-E_{a}/(RT)}$$, which of the following would not increase the rate constant of the reaction?
  • A new value of the constant $$A$$ was calculated, this new value being higher than the previous one
  • The temperature of the reaction is increased
  • Experiments have revealed that the previously accepted activation energy of the reaction was calculated incorrectly. The new value is larger.
  • The universal gas constant was redetermined to a smaller value
Here is another look at the reaction of crystal violet with sodium hydroxide, a first-order reaction (In $$A$$ v time):
What is the significance of the slope?
536905_7987007d1d2c47d2b0ff382267505c15.png
  • 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.
In a zero-order reaction, if the initial concentration of the reactant is doubled, the time required for half the reactant to be consumed:
  • increases two-fold
  • increases four-fold
  • decreases by half
  • does not change
A zero-order reaction, $$A \rightarrow$$ Product, with an initial concentration $$ { \left[ A \right]  }_{ 0 }$$ has a half-life of $$0.2 s$$. If one starts with the concentration $$2{ \left[ A \right]  }_{ 0 }$$, then the half-life is:
  • $$0.1 s$$
  • $$0.4 s$$
  • $$0.2 s$$
  • $$0.8 s$$
Decomposition of $$NH_3$$ on gold surface follows zero order kinetics. If rate constant $$K$$ is $$5\times 10^{-4}M$$ $$s^{-1}$$, rate of formation of $$N_2$$ will be:
  • $$10^{-3}M\ s^{-1}$$
  • $$2.5\times 10^{-4}M \ s^{-1}$$
  • $$5\times 10^{-4}M \ s^{-1}$$
  • zero
Acid hydrolysis of ester is 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 :
  • $${ V }_{ \infty }={ V }_{ t }$$
  • $${ V }_{ \infty }=\left( { V }_{ t }-{ V }_{ 0 } \right) $$
  • $${ V }_{ \infty }=2{ V }_{ t }-{ V }_{ 0 }$$
  • $${ V }_{ \infty }=2{ V }_{ t }+{ V }_{ 0 }$$
The rate of a particular reaction triples when temperature changes from $$50^o$$C to $$100^o$$C. What is the activation energy of the reaction (in $$J.mol^{-1}$$)? $$(log 3=0.4771, R=8.314K^{-1}mol^{-1})$$
  • $$24.012\times 10^{-3}$$
  • $$24.012\times 10^3$$
  • $$22.012\times 10^{-3}$$
  • $$22.012\times 10^3$$
The formation of $$H_2O_2$$ in the upper atmosphere follows the mechanism: $$H_2O+O\rightarrow 2OH \rightarrow H_2O_2$$; $$\Delta H=72\ kJ mol^{-1}$$, $$E_a=77\ kJ$$ $$mol^{-1}$$. 

Then, $$E_a$$ for the backward reaction will be (per mol):
  • $$-149$$ kJ
  • $$+149$$ kJ
  • $$-5$$ kJ
  • $$+5$$ kJ
At room temperature, the reaction between $$NO$$ and $$O_2$$ to give $$NO_2$$ is fast while that of between $$CO$$ and $$O_2$$ is slow. It is because:
  • The intrinsic energy of the reaction $$2NO+O_2\rightleftharpoons 2NO_2$$ is less
  • $$CO$$ is smaller in size than that of $$NO$$
  • $$CO$$ is poisonous
  • The activation energy for the reaction $$2NO+O_2\rightleftharpoons 2NO_2$$ is less
$$K_{p}$$ of a reaction at $$300\ K$$ is $$6\ atm$$ and $$2\ atm$$ at $$450\ K$$. Which of the following statements is incorrect about this reaction, if $$\triangle n_{g} = 1$$?
  • The reaction is exothermic
  • The rate of backward reaction increases more than that of forward reaction with increase in temperate
  • $$E_{a}$$ for the forward reaction is more than that of backward reaction
  • The difference between heat of reaction at constant pressure and that at constant volume is $$RT$$
What is the formula to find the value of $$t_{1/2}$$ for a zero order reaction?
  • $$\dfrac {k}{[R]_{0}}$$
  • $$\dfrac {2k}{[R]_{0}}$$
  • $$\dfrac {[R]_{0}}{2k}$$
  • $$\dfrac {0.693}{k}$$
0:0:1


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