CBSE Questions for Class 12 Engineering Chemistry Chemical Kinetics Quiz 4 - MCQExams.com

The rate constant of a zero order reaction is $$0.2\:mol\:dm^{-3}h^{-1}$$. If the concentration of the reactant after 30 minutes is $$0.05\:mol\:dm^{-3}$$. Then its initial concentration would be:
  • $$0.15\:mol\:dm^{-3}$$
  • $$1.05\:mol\:dm^{-3}$$
  • $$0.25\:mol\:dm^{-3}$$
  • $$4,00\:mol\:dm^{-3}$$
90% of a first order reaction was completed in 100 min. How much time it will take for 80% completion of a reaction :
  • 90 min
  • 80 min
  • 70 min
  • 60 min
The thermal decomposition of a compound is of first order. If 50% of a sample of the compound is decomposed in 120 min how long will it take for 90% of the compound to decompose ?
  • 399 min
  • 410 min
  • 250 min
  • 120 min
In a zero order reaction half life is 100 sec. After how much time 78 fraction of reactant will be reacted?
  • 300 sec
  • 200 sec
  • 175 sec
  • 25 sec
The half-life period of a first order reaction is $$15\: minute.$$ How much reaction will be completed in $$30\:minute$$?
  • $$\;75\%$$
  • $$\;80\%$$
  • $$\;95\%$$
  • $$\;100\%$$
$$70\%$$ of a first order reaction was completed in $$70\ min$$. What is the half-life of the reaction?
  • $$4.2\ min$$
  • $$42\ min$$
  • $$4.2\ hr$$
  • $$42\ s$$
A radioactive sample has a half-life period 1500 years. A sealed tube containing 1 g of the sample will contain _________ after 3000 year.
  • 1 g of the sample
  • 0.5 g of the sample
  • 0.25 g of the sample
  • 0.025g of the sample
The half-life period of a radioactive substance is 20 minutes. The time taken for 1 g of the substance to reduce to 0.25g will be:
  • 30 minutes
  • 40 minutes
  • 60 minutes
  • 10 minutes
For a reaction $$2A + B \rightarrow$$ product, rate law is :
$$-\displaystyle \frac{d[A]}{dt}=k[A]$$
At a time when $$t =\displaystyle \frac{1}{k},$$ concentration of the reactant is : ($$C_0 =$$ initial concentration)
  • $$\displaystyle \frac{C_0}{e}$$
  • $$C_0e$$
  • $$\displaystyle \frac{C_0}{e^2}$$
  • $$\displaystyle \frac{1}{C_0}$$
80% of a first order reaction was completed in 70 min. How much time will it take for 90% completion of a reaction?
  • 114 min
  • 140 min
  • 100 min
  • 200 min
A reaction which is of first order w.r.t reactant $$A$$, has a rate constant $$6$$ $${min}^{-1}$$. If we start with $$[A]=0.5mol$$ $${L}^{-1}$$, when would $$[A]$$ reach the value of $$0.05 mol$$ $${L}^{-1}$$?
  • $$0.384min$$
  • $$0.15min$$
  • $$3min$$
  • $$3.84min$$
For the reaction: $${H}_{2}+{Cl}_{2}\overset { sunlight }{ \longrightarrow}2HCl$$ the order of reaction is :
  • $$0$$
  • $$2$$
  • $$1$$
  • $$3$$
At 500 K, the half-life period of a gaseous reaction at an initial pressure of 80 kPa is 350 s. When the pressure is 40 kPa, the half-life period is 175 s. The order of the reaction is:
  • zero
  • one
  • two
  • three
A mixture of 2 gases -A (reactive) and X (inert) is kept in a closed flask when A decomposes as per the following roaction at 500 k
$$\displaystyle A(g)\rightarrow 2B(g)\rightarrow 2B(g)+3C(\varphi )+4D(s)$$
$$\displaystyle P^{\circ}=210mm Hg$$
$$\displaystyle P_{t}(10\, mins)=330mm\, Hg$$
$$\displaystyle P_{\infty t}=430mm\, Hg$$
Vapour pressure of $$\displaystyle C(\varphi )$$ at 500 K is 20 mm Hg
Calculate the half-life of A ?
  • 5 mins
  • 10 mins
  • 12 mins
  • Given data is not sufficient to answer

When sugar is stirred with a spoon in a glass of water, more sugar is dissolved and faster. Why?
  • Spoon acts as a catalyst
  • On stirring, temperature increases
  • Stirring increases the rate of interaction
  • Spoon increases the attraction between the molecules of water and sugar
The time required for $$100\%$$ completion of a zero order reaction is:
  • $$ak$$
  • $$\dfrac{a}{2k}$$
  • $$\dfrac{a}{k}$$
  • $$\dfrac{2k}{a}$$
Which among the following reactions is an example of instantaneous reaction under normal condition?
  • $$2{H}_{2}+{O}_{2}\rightarrow 2{H}_{2}O$$
  • $${N}_{2}+{O}_{2}\rightarrow 2NO$$
  • $$NaOH+HCl\rightarrow NaCl+{H}_{2}O$$
  • $${C}_{12}{H}_{22}{O}_{11}+{H}_{2}O\rightarrow {C}_{6}{H}_{12}{O}_{6}+{C}_{6}{H}_{12}{O}_{6}$$
Which of the following expression is correct for first order reactions ($$c_0$$ refers to initial concentration of reactant) ?
  • $$t_{1/2}\, \propto\, c_0$$
  • $$t_{1/2}\, \propto\, c_0^{-1}$$
  • $$t_{1/2}\, \propto\, c_0^{-2}$$
  • $$t_{1/2}\, \propto\, c_0^0$$
$$99\%$$ at a first order reaction was completed in $$32\:min.$$ when will $$99.9\%$$ of the reaction complete.(in min) :
  • 48
  • 46
  • 50
  • 45
The rate equation for a reaction, $$\displaystyle A\longrightarrow B$$ is $$\displaystyle r={ k\left[ A \right] }^{ 0 }$$. If the initial concentration of the reactant is $$a$$ $$mol.{ dm }^{ -3 }$$, the half-life period of the reaction is:
  • $$\displaystyle \frac { a }{ 2k } $$
  • $$\displaystyle \frac { k }{ a } $$
  • $$\displaystyle \frac { a }{ k } $$
  • $$\displaystyle \frac { 2a }{ k } $$
The time taken for $$10$$% completion of a first order reaction is $$20$$ min. Then, for $$19$$% completion, the reaction will take:
  • $$40$$ min
  • $$60$$ min
  • $$30$$ min
  • $$50$$ min
For a zero order reaction :
  • $${ t }_{ 1/2 }\propto { R }_{ o }$$
  • $${ t }_{ 1/2 }\propto \dfrac{1}{{ R }_{ o }}$$
  • $${ t }_{ 1/2 }\propto { R }_{ o }^{ 2 }$$
  • $${ t }_{ 1/2 }\propto \dfrac{1}{{ R }_{ o }^{2 }}$$
For a reaction $$X\longrightarrow\ Y$$, the graph of the product concentration (x) versus time (t) came out to be straight line passing through the origin. Hence the graph of $$\cfrac{-d[X]}{dt}$$ and time would be:
  • straight line with a negative slope and an intercept on y-axis
  • straight line with positive slope and an intercept on y-axis
  • a straight line parallel to x-axis
  • a hyperbola
A first order reaction is given as $$A\rightarrow$$ products. Its integrated equation is:
  • $$k=\dfrac{2.303}{t}log\dfrac{a-x}{a}$$
  • $$k=\dfrac{1}{t}log\dfrac{a}{a-x}$$
  • $$k=\dfrac{2.303}{t}log\dfrac{a}{a-x}$$
  • $$-k=\dfrac{1}{t}log\dfrac{a-x}{a}$$
The relationship between rate constant and half-life period of zero order reaction is given by:
  • $$\displaystyle t_{1/2} = [A_0]2k$$
  • $$\displaystyle t_{1/2} = \frac{0.693}{k}$$
  • $$\displaystyle t_{1/2} = \frac{[A_0]}{2k}$$
  • $$\displaystyle t_{1/2} = \frac{2[A_0]}{2k}$$
In the first order reaction, 75% of the reactant gets disappeared in 1.386 h. The rate constant of the reaction is:
  • $$3.0 \times { 10 }^{ -3 }{ s }^{ -1 }$$
  • $$2.8 { \times 10 }^{ -4}{ s }^{ -1 }$$
  • $$17.2 { \times 10 }^{ -3 }{ s }^{ -1 }$$
  • $$1.8 { \times 10 }^{ -3 }{ s }^{ -1 }$$
The first order integrated rate equation is:
  • $$k\, =\, \displaystyle \frac {x}{t}$$
  • $$k\, =\, -\displaystyle \frac {2.303}{t}\, log\, \displaystyle \frac {\alpha}{\alpha\, -\, x}$$
  • $$k\, =\, \displaystyle \frac {1}{t}\, ln\, \displaystyle \frac {\alpha}{\alpha\, -\, x}$$
  • $$k\, =\, \displaystyle \frac {1}{t}\, ln \displaystyle \frac {x}{\alpha(\alpha\, -\, x)}$$
Found the enthalpy change of the forward reaction ?

480955.JPG
  • B
  • C
  • D
  • E
Assertion: Reactions happen faster at higher temperatures.
Reason: As temperatures increase, there is also an increase in the number of collisions with the required activation energy for a reaction to occur.
  • Both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
  • Both Assertion and Reason are false
The minimum energy required for molecules to react and form compounds can be defined as :
  • Reduction potential
  • Ionization energy
  • Electronegativity
  • Heat of formation
  • Activation energy
The time required for $$100\%$$ completion of zero order reaction is:
  • $$\displaystyle\frac{a}{k}$$
  • $$\displaystyle\frac{a}{2k}$$
  • $$\displaystyle\frac{2a}{k}$$
  • $$\displaystyle\frac{k}{a}$$
In a reaction, the potential energy of the reactants is 40 kJ/mol, the potential energy of the products is 10 kJ/mol and the potential energy of the activated complex is 55 kJ/mol. What is the activation energy for the reverse reaction?
  • 45 kJ/mol
  • -30 kJ/mol
  • 15 kJ/mol
  • 35 kJ/mol
  • -55 kJ/mol
Assertion: Increasing the concentration of reactants will cause a reaction to proceed faster.
Reason: More reactants lowers the activation energy of a reaction.
  • Both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
  • Both Assertion and Reason are false
In a first order reaction, the concentration of the reactant decreases from 0.6 M to 0.3 M in 15 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M in minutes is:
  • 1.2
  • 12
  • 30
  • 3
The addition of a catalyst to a reaction changes which of the following?
  •  Activation energy
  •  Entropy
  • Enthalpy
  •  Nature of the products
How an increase in concentration is related to number of collisions?
  • Directly
  • Inversely
  • Has no effect
  • None
Based on the following reaction and rate data:
$$\displaystyle A\left( g \right) +B\left( g \right) \rightarrow products$$

Experiment$$[A]$$ mol/L$$[B]$$ mol/LInitial Rate (M/s)
10.0600.0100.040
20.0300.0100.040
30.0300.0200.080
What is the order of the reaction with respect to $$A$$?
  • 0
  • 1
  • 2
  • 3
  • 4
What does the exponential factor represent?
  • The total number of reactants in a reaction.
  • The amount of energy needed to start a chemical reaction.
  • The fraction of reactants that have approached the activation energy hill and made it over per number of attempts.
  • The fraction of reaction energy given off per unit of time.
  • The fraction of products that have approached the activation energy hill and made it over per number of attempts.
Based on the following reaction and rate data:
$$\displaystyle A\left( g \right) +B\left( g \right) \rightarrow products$$

Experiment$$[A]$$ mol/L$$[B]$$ mol/LInitial Rate (M/s)
10.0600.0100.040
20.0300.0100.040
30.0300.0200.080
What is the order of the reaction with respect to $$B$$?
  • 0
  • 1
  • 2
  • 3
  • 4
Refer to the heating curve for $$H_{2}O$$ above.
Which region indicates a solid?

496907_83782dfd16a34401b2b110a886412264.png
  • A
  • B
  • C
  • D
  • E
Refer to the heating curve for $$H_{2}O$$ above.
Where is the temperature of $$H_{2}O$$ changing at $$\dfrac {1^{\circ}C}{g.cal}$$?

496906_41a9a53158a04d5bb268b2a48f1a5351.png
  • A
  • B
  • C
  • D
  • E
Assertion: The rate of the reaction of iron and hydorchloric acid will increase if the iron pieces are cut into smaller pieces.
Reason: Increasing surface area of a reactant helps to reduce activation energy.
  • Both Assertion and Reason are true and Reason is the correct explanation of Assertion
  • Both Assertion and Reason are true but Reason is not the correct explanation of Assertion
  • Assertion is true but Reason is false
  • Assertion is false but Reason is true
  • Both Assertion and Reason are false
Which letter shows the potential energy of the products?
496903_b0fcb4be4dd04e3288562e141d44f077.png
  • A
  • B
  • C
  • D
  • E
In a multistep chemical process, the rate-limiting step is the step in the reaction with the :
  • Highest activation energy & fastest reaction rate
  • Highest activation energy & slowest reaction rate
  • Lowest activation energy & fastest reaction rate
  • Lowest activation energy & slowest reaction rate
  • Greatest concentration of the reactants and products
Statement I : Catalysts decrease the rate of a chemical reaction
Because
Statement II : Catalysts decrease activation energy
  • Statement 1 and Statement 2 are correct and Statement 2 is the correct explanation of Statement 1 .
  • Both the Statement 1 and Statement 2 are correct and Statement 2 is not the correct explanation of Statement 1.
  • Statement 1 is correct but Statement 2 is not correct.
  • Statement 1 is not correct but Statement 2 is correct.
  • Both the Statement 1 and Statement 2 are not correct.
Which reaction in the diagram has the lowest activation energy?
525816.PNG
  • $$A$$
  • $$B$$
  • $$C$$
  • $$D$$
  • All reactions have equal activation energy
How would the activation energy of the reaction diagram above be affected by an increase in temperature?
536868_79eafdddd79a480cb9d90e37a50b181b.png
  • The activation energy curve would grow taller.
  • The activation energy curve would grow shorter.
  • The activation energy curve would become inverted.
  • The activation energy curve would not be affected by an increase in temperature.
In the following image, which reverse reaction has the highest activation energy?
537807_52e6f9a35f8d4fe9a0a31bd5b0f4cff0.png
  • E to D
  • G to E
  • C to A
  • This cannot be determined from the given information.
Two molecules collide and a reaction not occur. Which of the following is not a valid explanation for this?
  • The molecules were not in the proper states of matter.
  • The molecules did not have enough kinetic energy.
  • The molecules were not oriented correctly when they struck each other.
  • The temperature of the reaction mixture was not high enough.
Activation energy, by definition, is the minimum amount of energy required for reactants to form products. Which of the following is not true of activation energy?
  • The value of activation energy varies from reaction to reaction.
  • If molecules are moving fast enough, the collisions will result in kinetic energy that can be used to bend, stretch, and eventually break the bonds of the reactants releasing the potential energy in a usable form.
  • All reactions eventually form an intermediate that lowers the overall energy requirements of the reaction resulting in a relatively reasonable activation energy.
  • Reactants only form products if the activation energy barrier has been exceeded with usable kinetic energy from the system and /or surroundings.
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