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Introduction to chemical kinetics - class-XII

introduction to chemical kinetics

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Questions

Question 1 Multiple Choice (Single Answer)

Fill up the following with suitable terms.

(i) Activation energy $=$ Threshold energy $-$ _______.

(ii) Half-life period of zero order reaction $=$ ________.

(iii) Average rate of reaction $=$ _______.

(iv) Instantaneous rate of reaction $=$ ______.

  1. Potential energy, $\dfrac {0.693}{k}, \dfrac {dx}{dt}, \dfrac {\triangle [A]}{\triangle t}$
  2. Energy of reactants, $\dfrac {1}{k}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$
  3. Energy of reaction, $\dfrac {\log k}{t}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$
  4. Average kinetic energy of reactants, $\dfrac {a}{2k}, \dfrac {\triangle [A]}{\triangle t}, \dfrac {dx}{dt}$
Question 2 Multiple Choice (Single Answer)

Chemical kinetics a branch of physical chemistry deals with:

  1. structure of molecules
  2. heat changes in a reaction
  3. physical changes in a reaction
  4. rate of reactions
Question 3 Multiple Choice (Single Answer)

If reaction A and B are given with Same temperature and same concentration but rate of $A$ is double than $B$. Pre exponential factor is same for both the reaction then difference in activation energy $E _{A} - E _{B}$ is?

  1. $-RT\ ln2$
  2. $RT\ ln2$
  3. $2RT$
  4. $\dfrac {RT}{2}$
Question 4 Multiple Choice (Single Answer)

Which of the following theory is not related to the chemical kinetics?

  1. Collision theory
  2. Absolute theory
  3. Absolute reaction rate
  4. VSEPR theory
Question 5 Multiple Choice (Single Answer)

Chemical kinetics, a branch of physical chemistry, deals with:

  1. heat changes in a reaction
  2. physical changes in a reaction
  3. rate of reactions
  4. structure of molecules
Question 6 Multiple Choice (Single Answer)
The rate of chemical reaction is directly proportional to the equilibrium constant.
In which of the following process reaction will be completed first?
  1. $K=10$
  2. $K=1$
  3. $K={ 10 }^{ 3 }$
  4. $K={ 10 }^{ -2 }$
Question 7 Multiple Choice (Single Answer)
Find out the correct order of rate of reaction towards allylic substitution :
(I) $CH _3 - CH = CH _2$
(II) $CH _3 -CH _2 - CH = CH _2$
(III) $CH _3 - \overset{CH _3}{\overset{\!\!\!\!\!\!|}{CH}} - CH = CH _2$
  1. ${\rm{I}}\,\,{\rm{ > }}\,\,{\rm{II}}\,\,{\rm{ > }}\,\,{\rm{III}}$
  2. ${\rm{II}}\,\,{\rm{ > }}\,\,{\rm{I}}\,\,{\rm{ > }}\,\,{\rm{III}}$
  3. ${\rm{III}}\,\,{\rm{ > }}\,\,{\rm{I}}\,\,{\rm{ > }}\,\,{\rm{II}}$
  4. ${\rm{III}}\,\,{\rm{ > }}\,\,{\rm{II}}\,\,{\rm{ > }}\,\,{\rm{I}}$
Question 8 Multiple Choice (Single Answer)

A chemist puts a sample of dilute aqueous hydrochloric acid into beaker $1$. She adds a sample of zinc and measures the rate of production of hydrogen gas.
She then puts a different sample of dilute aqueous hydrochloric acid into beaker $2$. She adds a different sample of zinc and measure the rate of production of hydrogen gas.
The rate of the reaction in beaker $2$ is greater than the rate of the reaction in beaker $1$.
Which factors could help to explain this observation?
$1$. The reaction in beaker $1$ has a higher activation energy than the reaction in beaker $2$.
$2$. The zinc in beaker $1$ is in larger pieces than the zinc in beaker $2$.
$3$. The acid in beaker $1$ is at a lower concentration than the acid in beaker $2$.

  1. $1, 2$ and $3$ are correct
  2. $1$ and $2$ only are correct
  3. $2$ and $3$ only are correct
  4. $1$ only is correct
Question 9 Multiple Choice (Single Answer)

The approach to the following equilibrium was observed kinetically from both directions:
$ Pt{ Cl } _{ 4 }^{ -2 }+H _{ 2 }O\rightleftharpoons Pt(H _{ 2 }O)CI _{ 3 }+Cl^{ - } $
At $ 25^o C,$  it was found that  $ -\dfrac { d[PtC{ l } _{ 4 }^{ 2- }] }{ dt } =(3.9  \times 10^{ -5 } s^{ -1 }) [PtC{ l } _{ 4 }^{ 2- }]-(2.1  \times 10^{ -3 } L mol^{ -1 }s^{ -1 }) [Pt(H _{ 2 }O)C{ l } _{ 3 }^{ - }][Cl^{ - }] $
The value of $ K _{eq} $ (equilibrium constant) for the complexation of the fourth $ cl^- $ by $ Pt( II ) $ is

  1. $ 53.8 mol L^{-1} $
  2. $ 0.018 mol L^{-1} $
  3. $ 53.8 L mol^{-1} $
  4. $ 0.018 L mol^{-1} $
Question 10 Multiple Choice (Multiple Answers)

Which statements are correct in terms of chemical kinetic stuides?

  1. The quenching of a reaction can be made by cooling the reaction mixture.
  2. The quenching of a reaction can be made by diluting the reaction mixture.
  3. The reaction is supposed to be completed if it is kept for long time or strongly heated.
  4. None of the above
Question 11 Multiple Choice (Single Answer)

What does the exponential factor represent?

  1. The total number of reactants in a reaction.
  2. The amount of energy needed to start a chemical reaction.
  3. The fraction of reactants that have approached the activation energy hill and made it over per number of attempts.
  4. The fraction of reaction energy given off per unit of time.
  5. The fraction of products that have approached the activation energy hill and made it over per number of attempts.
Question 12 Multiple Choice (Single Answer)

In a reaction mechanism consisting of elementary reaction steps where the relative rate of each is given, which of the following is most likely to be the rate-determining step?

  1. A step labeled fast
  2. A step labeled moderate
  3. A step labeled slow
  4. It is not possible to tell which step is rate determining from this information.
Question 13 Multiple Choice (Single Answer)

Statement: The rate of instantaneous reactions can be determined experimentally.


State whether the given statement is true or false.

  1. True
  2. False
Question 14 Multiple Choice (Single Answer)
If the rate with respect to $O _2, NO, NO _2$ are $\displaystyle \frac{- \Delta [O _2]}{\Delta t}$ $= \dfrac{-1}{2}\dfrac{\Delta [NO]}{\Delta t}$, $= \dfrac{+1}{2} \dfrac{\Delta [NO _2]}{\Delta t}$, then the corresponding chemical equation is $2NO+O _2  \rightarrow NO _2$.
  1. True
  2. False
Question 15 Multiple Choice (Single Answer)

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. $1.6\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$
  2. $8.0\times { 10 }^{ -4 }kg\quad { min }^{ -1 }$
  3. $3.2\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$
  4. $1.28\times { 10 }^{ -3 }kg\quad { min }^{ -1 }$
Question 16 Multiple Choice (Single Answer)

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 -

  1. Decrease by $3$ times
  2. Increased by $9$ times
  3. Increase by $3$ times
  4. Unpredictable
Question 17 Multiple Choice (Multiple Answers)

The study of chemical kinetics becomes highly complicate if there occurs:

  1. reversible reaction
  2. side reaction
  3. surface reaction
  4. none of these
Question 18 Multiple Choice (Single Answer)

The container of $2$ litrer contains $4$ mole of $N _{2}O _{5}$. On heating to $100^{\circ}C, N _{2}O _{5}$ undergoes complete dissociation to $NO _{2}$ and $O _{2}$. Select the correct answers if rate constant for decomposition of $N _{2}O _{5}$ is $6.2\times 10^{-4}sec^{-1}$.
1. The mole ratio before and after dissociation is $4 : 2$
2. Half life of $N _{2}O _{5}$ is $1117\ sec$ and it is independent of concentration.
3. Time required to complete $40$% of reaction is $824\ sec$.
4. If volume of container is doubled, the initial rate of decomposition becomes half of the initial rate.

  1. $1, 3, 4$
  2. $1, 2, 3, 4$
  3. $3, 4$
  4. $2, 3, 4$
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