Chemistry-class-12-html_c-12-chemical-kinetics

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (c)

The role of a catalyst is to change the activation energy of reaction. This is done by either increasing or decreasing activation energy of molecule as catalyst are mainly of two types; +ve catalyst and -ve catalyst.

**Note** Catalyst are of two types one is positive catalyst which increases rate of reaction by decreasing activation energy and another is negative catalyst which decreases rate of reaction by increasing energy of activation.

</div>

</main>

<hr>

<footer> <font size = "4"> <span style="color:blue">MCQ (Single correct option)</span> $\rarr$ MCQ (More than one correct questions) $\rarr$ Short answer type questions $\rarr$ Matching the columns $\rarr$ Assertion and Reason $\rarr$ Long answer type questions  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Consider figure and mark the correct option.

(a) Activation energy of forward reaction is $E_1+E_2$ and product is less stable than reactant

(b) Activation energy of forward reaction is $E_1+E_2$ and product is more stable than reactant

(d) Activation energy of backward reaction is $E_1$ and product is more stable than reactant

</div>

</div>
<div  style='float: right; width:35%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Consider a first order gas phase decomposition reaction given below

$A(g) \to B(g)+C(g)$

The initial pressure of the system before decomposition of $A$ was $p_i$. After lapse of time ' $t$ ' total pressure of the system increased by $x$ units and became ' $p_t$ '. The rate constant $k$ for the reaction is given as

(a) $k=\frac{2.303}{t} \log \frac{p_i}{p_i-x}$

(b) $k=\frac{2.303}{t} \log \frac{p_i}{2 p_i-p_t}$

(d) $k=\frac{2.303}{t} \log \frac{p_i}{p_i+x}$

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (b)

$ \underset{\text{At time t}}{\underset{Initially}{}}  \quad \underset{p_i^{-x}}{\underset{p_i}{A(g)}} \longrightarrow \underset{x}{\underset{0}{B(g)}} + \underset{x}{\underset{0}{C(g)}}$

$
\text{ For first order reaction } \quad x=p_t-p_i
$

$ k= \frac{2.303}{t}log \frac{p_i}{p_i-x} $

$ = \frac{2.303}{t}log \frac{p_i}{p_i-(p_t-p_i)} $

$ = \frac{2.303}{t}log \frac{p_i}{2p_i-p_t} $

</font>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** According to Arrhenius equation rate constant $k$ is equal to $A e^{-E_a / R T}$ Which of the following options represents the graph of $\ln k v s \frac{1}{T}$ ?
 
(a)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-077.jpg?height=305&width=339&top_left_y=482&top_left_x=402" width ="200px">
$\quad \quad \quad \quad $(b)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-077.jpg?height=300&width=342&top_left_y=485&top_left_x=930" width ="200px">

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

(c)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-077.jpg?height=310&width=339&top_left_y=797&top_left_x=402" width ="200px">

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

(d)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-077.jpg?height=308&width=342&top_left_y=798&top_left_x=930" width ="200px">

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

This equation can be related to equation of straight line as shown above.

From the graph, it is very clear that slope of the plot $=\frac{-E_a}{R}$ and intercept $=\ln A$.

**Explanation**

This problem include graphical representation of Arrhenius equation. To solve this problem transform the Arrhenius equation into equation of straight line taking $\ln k$ on $x$-axis and $\frac{1}{T}$ on $y$-axis

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Consider the Arrhenius equation given below and mark the correct option.

$
k=A e^{-\frac{E_a}{RT}}
$

(a) Rate constant increases exponentially with increasing activation energy and decreasing temperature

(b) Rate constant decreases exponentially with increasing activation energy and decreasing temperature

(d) Rate constant increases exponentially with decreasing activation energy and increasing temperature

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** A graph of volume of hydrogen released vs time for the reaction between zinc and dil. $HCl$ is given in figure. On the basis of this mark the correct option.

(a) Average rate upto $40 s$ is $\frac{V_3-V_2}{40}$

(b) Average rate upto $40 s$ is $\frac{V_3-V_2}{40-30}$

(d) Average rate upto $40 s$ is $\frac{V_3-V_1}{40-20}$

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Which of the following statements is not correct about order of a reaction?

(a) The order of a reaction can be a fractional number

(b) Order of a reaction is experimentally determined quantity

(c) The order of a reaction is always equal to the sum of the stoichiometric coefficients of reactants in the balanced chemical equation for a reaction

(d) The order of a reaction is the sum of the powers of molar concentration of the reactants in the rate law expression

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Consider the graph given in figure. Which of the following options does not show instantaneous rate of reaction at 40 s?

(a) $\frac{V_5-V_2}{50-30}$

(b) $\frac{V_4-V_2}{50-30}$

(d) $\frac{V_3-V_1}{40-20}$

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (b)

Reaction occurring at smallest time interval is known as instantaneous rate of reaction e.g., instantaneous rate of reaction at $40 s$ is rate of reaction during a small interval of time close to $40 s$. Volume change during a small time interval close to $40 s$ i.e., $40-30$ s, $50-40 s, 50-30 s, 40-20 s$.

Instantaneous rate of reaction $=\frac{\text{ Change in volume }}{\text{ Time interval close to } 40 s}$
 
(a) $r   _{\text{inst }}(20 s)=\frac{V_5-V_2}{50-30}$ correct

(b) $r   _{\text{inst }}(20 s)=\frac{V_4-V_3}{50-30}$ incorrect, correct is $\frac{V_5-V_3}{50-30}$

(d) $r   _{\text{inst }}(20 s)=\frac{V_3-V_1}{40-20}$ correct

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Which of the following statements is correct?

(a) The rate of a reaction decreases with passage of time as the concentration of reactants decreases

(b) The rate of a reaction is same at any time during the reaction

(d) The rate of a reaction decreases with increase in concentration of reactant (s)

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (a)

Rate of reaction is defined as rate of decrease of concentration of any one of reactant with passage of time

$
\begin{aligned}
\text{ Rate of reaction } & =\frac{\text{ Rate of disappearance of reactant }}{\text{ Time taken }} \\\\\\
r & =\frac{-d x}{d t}
\end{aligned}
$

Thus, as the concentration of reactant decreases with passage of time, rate of reaction decreases.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Which of the following expressions is correct for the rate of reaction given below?

$
5 Br^{-}(a q)+BrO_3^{-}(a q)+6 H^{+}(a q) \to 3 Br_2(a q)+3 H_2 O(l)
$

(a) $\frac{\Delta[Br^{-}]}{\Delta t}=5 \frac{\Delta[H^{+}]}{\Delta t}$

(b) $\frac{\Delta[Br^{-}]}{\Delta t}=\frac{6}{5} \frac{\Delta[H^{+}]}{\Delta t}$

(d) $\frac{\Delta[Br^{-}]}{\Delta t}=6 \frac{\Delta[H^{+}]}{\Delta t}$

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (c)

Given, chemical reaction is

$
5 Br^{-}(aq)+BrO_3^{-}(aq)+6 H^{+}(aq) \longrightarrow 3 Br_2(aq)+3 H_2 O(l)
$

Rate law expression for the above equation can be written as

$ -\frac{1}{5} \frac{\Delta[Br^{-}]}{\Delta t}=-\frac{\Delta[BrO_3^{-}]}{\Delta t}=\frac{-1}{6} \frac{\Delta[H^{+}]}{\Delta t}=\frac{+1}{3} \frac{\Delta[Br_2]}{\Delta t} $

$ \Rightarrow  \frac{\Delta[Br^{-}]}{\Delta t}  =-\frac{\Delta[BrO_3^{-}]}{\Delta t}=\frac{-5}{6} \frac{\Delta[H^{+}]}{\Delta t} $

$  \Rightarrow  \frac{\Delta[Br^{-}]}{\Delta t}  =\frac{5}{6} \frac{\Delta[H^{+}]}{\Delta t} $

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (a)

The chemical reaction in which energy is evolved during the reaction is known as exothermic reaction i.e., activation energy of product is greater than activation energy of reactants.

Here, only (I) denotes correct picture of exothermic reaction.

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Which of the following statements is incorrect about the collision theory of chemical reaction?

(a) It considers reacting molecules or atoms to be hard spheres and ignores their structural features

(b) Number of effective collisions determines the rate of reaction

(d) Molecules should collide with sufficient threshold energy and proper orientation for the collision to be effective

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (d)

The time taken for half the reaction to complete. i.e., the time in which the concentration of a reactant is reduced to half of its original value is called half-life period of the reaction.

</div>

But it is impossible to perform $100 \%$ of the reaction. Whole of the substance never reacts because in every half-life, $50 \%$ of the substance reacts. Hence, time taken for $100 \%$ completion of a reaction is infinite.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Compounds ' $A$ ' and ' $B$ ' react according to the following chemical equation.

$
A(g)+2 B(g) \longrightarrow 2 C(g)
$

Concentration of either ' $A$ ' or ' $B$ ' were changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

<div style='float: left; width:100%; text-align: left;font-size:20px'>
 
| Experiment | Initial concentration of $[\boldsymbol{{}A}] / \mathbf{m o l ~ L}^{-\mathbf{1}}$ | Initial concentration of $[\boldsymbol{{}B}] / \mathbf{m o l ~ L}^{-\mathbf{1}}$ | Initial concentration of $[C] / m o l  L^{-1} s^{-1}$ |
| :---: | :---: | :---: | :---: |
| 1. | 0.30 | 0.30 | 0.10 |
| 2. | 0.30 | 0.60 | 0.40 |
| 3. | 0.60 | 0.30 | 0.20 |

(a) Rate $=k[A]^{2}[B]$

(b) Rate $=k[A][B]^{2}$

(d) Rate $=k[A]^{2}[B]^{0}$

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Which of the following statement is not correct for the catalyst?

(a) It catalyses the forward and backward reactions to the same extent

(b) It alters $\Delta G$ of the reaction

(d) It provides an alternate mechanism by reducing activation energy between reactants and products

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer** (b)

Characteristics of catalyst
 
(a) It catalyses the forward and backward reaction to the same extent as it decreases energy of activation hence, increases the rate of both the reactions.

(b) Since, reaction quotient is the relation between concentration of reactants and products. Hence, catalyst does not alter Gibbs free energy as it is related to reaction quotient. Thus, Gibbs free energy does not change during the reaction when catalyst is added to it.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Answer**

$(\boldsymbol{{}a}, \boldsymbol{{}b})$ Pseudo first order reaction is a chemical reaction in which rate of reaction depends upon concentration of only one reactant while concentration of another reactant has no effect on rate of reaction.

e.g., hydrolysis of ethyl acetate in presence of excess of water

$
\begin{gathered}
CH_3 COOC_2 H_5+\underset{\text{ excess }}{H_2 O} \xrightarrow{H^{+}} CH_3 COOH+C_2 H_5 OH \\\\\\
r=k[CH_3 COO C _2 H_5]^{2}[H_2 O]^{0}
\end{gathered}
$

Excess $[H_2 O]$ can cause the independency of reaction on $H_2 O$.

Hence, (a) is the correct choice.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (Single correct option)** </Primary>

<hr>

<main>

**Ques.** Consider the reaction $A \longrightarrow B.$
The concentration of both the reactants and the products varies exponentially with time. Which of the following figures correctly describes the change in concentration of reactants and products with time?
 
(a)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-083.jpg?height=293&width=396&top_left_y=1685&top_left_x=388" width ="250px">
$\quad \quad \quad \quad \quad $(b)
<img src="https://imagedelivery.net/YfdZ0yYuJi8R0IouXWrMsA/b1b48f85-7aef-49bb-d8bf-b6d0b623ad00/public" width ="250px">

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(a, d)$

For a balanced chemical equation of an elementary reaction order is same as molecularity and molecularity can never be zero. If molecularity of a reaction is considered to be zero it mean that no reactant is going to transform into product. Consider a chemical reaction.

$ 2 NO(g)+O_2(g) \longrightarrow 2 NO_2(g) $

Differential rate law expression can be written as

$ \frac{d R}{d t}=k[NO]^{2}[O_2] $

Here, molecularity $=3$, order $=3$

</div>
</main>

<hr>

<footer> <font size = "4">  MCQ (Single correct option)  $\rarr$ <span style="color:blue">MCQ (More than one correct questions)</span> $\rarr$ Short answer type questions $\rarr$ Matching the columns $\rarr$ Assertion and Reason $\rarr$ Long answer type questions  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** For a complex reaction...... .

(a) order of overall reaction is same as molecularity of the slowest step

(b) order of overall reaction is less than the molecularity of the slowest step

(d) molecularity of the slowest step is never zero or non-integer

</div>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(a, d)$
 
(a) For a complex reaction, order of overall reaction = molecularity of slowest step As rate of overall reaction depends upon total number of molecules involved in slowest step of the reaction. Hence, molecularity of the slowest step is equal to order of overall reaction.

(d) Since, the completion of any chemical reaction is not possible in the absence of reactants. Hence, slowest step of any chemical reaction must contain at least one reactant. Thus, molecularity of the slowest step is never zero or non-integer.

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** At high pressure the following reaction is zero order.

$
2 NH_3(g) \frac{1130 K}{\text{ Platinum catalyst }} N_2(g)+3 H_2(g)
$

Which of the following options are correct for this reaction?

(a) Rate of reaction $=$ Rate constant

(b) Rate of the reaction depends on concentration of ammonia

(d) Further increase in pressure will change the rate of reaction

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(a, d)$

When the reactant molecules collide each other they lead to formation of an activated complex. It has highest energy among reactants, products and activated complex. When it decomposes to give product, energy is released and stability of product increases.

Since, the entire concentration of activated complex do not convert into products while, some activated complex may give reactants also.

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** According to Maxwell, Boltzmann distribution of energy,...... .

(a) the fraction of molecules with most probable kinetic energy decreases at higher temperatures

(b) the fraction of molecules with most probable kinetic energy increases at higher temperatures

(d) most probable kinetic energy decreases at higher temperatures

</div>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

Kinetic energy of maximum fraction of molecule is known as most probable kinetic energy. It is important to note that with increase of temperature, peak shifts forward but downward. This means that with increase of temperature,

(i) most probable kinetic energy increases.

(ii) the fractions of molecules possessing most probable kinetic energy decreases.

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** In the graph showing Maxwell, Boltzmann distribution of energy

(a) area under the curve must not change with increase in temperature

(b) area under the curve increases with increase in temperature

(d) with increase in temperature curve broadens and shifts to the right hand side

</div>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(a, d)$

According to Maxwell Boltzmann distribution curve, area under the curve must not change with increase in temperature. But with increase in temperature curve broadens and shift towards right hand side due to decrease in fraction of molecules having most probable kinetic energy.

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** Which of the following statements are in accordance with the Arrhenius equation?

(a) Rate of a reaction increases with increase in temperature

(b) Rate of a reaction increases with decrease in activation energy

(d) Rate of reaction decreases with decrease in activation energy

</div>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(b, d)$

**Function of Catalyst** As the catalyst is added to the reaction medium rate of reaction increases by decreasing activation energy of molecule. Hence, it follows an alternative pathway.

Catalyst does not change the enthalpy change of reaction. Energy of reactant and product remain same in both catalysed and uncatalysed reaction.

Hence, (a) and (d) are incorrect statements.

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** Which of the following graphs is correct for a zero order reaction?

(a)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-087.jpg?height=298&width=374&top_left_y=1438&top_left_x=428" width ="250px">
$\quad \quad \quad \quad \quad$(b)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-087.jpg?height=293&width=398&top_left_y=1443&top_left_x=834" width ="250px">

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

(c)

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

(d)

</div>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Ques.** Which of the following graphs is correct for a first order reaction?

(a)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-088.jpg?height=274&width=344&top_left_y=1313&top_left_x=463" width ="250px">
$ \quad \quad \quad  \quad \quad  \quad \quad$(b)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-088.jpg?height=274&width=356&top_left_y=1308&top_left_x=874" width ="250px">

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

(c)
<img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-088.jpg?height=335&width=363&top_left_y=1544&top_left_x=441" width ="250px">

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

(d)
 <img src="https://cdn.mathpix.com/cropped/2024_01_24_76a1a59bab5d20ee6cc6g-088.jpg?height=278&width=373&top_left_y=1602&top_left_x=856" width ="250px">

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

**Answer** $(a, $d)$

For the first order reaction

$
\begin{aligned}
& k=\frac{2.303}{t} \log \frac{[R]_0}{[R]} \\\\\\
& \frac{k t}{2.303}=\log \frac{[R]_0}{[R]} \\\\\\
& \begin{matrix}
\log \frac{[R]_0}{[R]} & =(\frac{k}{2.303}) &\times t&+0  \\\\\\
\uparrow & \uparrow & \uparrow & \uparrow \\\\\\
 y= &\quad m & \quad x &+c
\end{matrix}  \\\\\\
\end{aligned}
$

</font>

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **MCQ (More than one correct questions)** </Primary>

<hr>

<main>

Correct plot of $\log \frac{[R]_0}{[R]}$ can be represented by (d)

where,

$
\text{ slope }=\frac{k}{2.303}
$

The time taken for any fraction of the reaction to complete is independent of the initial concentration. Let, us consider it for half of the reaction to complete.

$t  =\frac{2.303}{k} \log \frac{a}{a-x} $

$\text{For half-life} \quad t  =t   _{1 \backslash 2} \text{ and } x=\frac{a}{2} $

</div>
</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Answer**

Presence of one of the reactants in excess, as in such a condition, its concentration remains constant and rate of such reaction depends upon concentration of one reactant only and reaction is known as pseudo first order reaction e.g., acid catalysed hydrolysis of ethyl acetate.

$
\underset{\text{ Ethyl acetate }}{CH_3 COOC_2 H_5}+H_2 O \xrightarrow[\text{ Acetic acid }]{H^{+}} \underset{\text{ Ethyl alcohol }}{CH_3 COOH}+\underset{2}{C_2 H_5 OH}
$

This reaction is bimolecular but is found to be of first order as experimentally it is observed that rate of reaction depends upon the concentration of ethyl acetate not on water as it is present in excess.

</div>

</main>

<hr>

<footer> <font size = "4">  MCQ (Single correct option)  $\rarr$  MCQ (More than one correct questions)  $\rarr$ <span style="color:blue">Short answer type questions</span> $\rarr$ Matching the columns $\rarr$ Assertion and Reason $\rarr$ Long answer type questions  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Answer**

We can determine the rate of this reaction as a function of initial concentrations either by keeping the concentration of one of the reactants constant and changing the concentration of the other reactant or by changing the concentration of both the reactants. e.g., for the given reaction,

(i) Keeping $[O_2]$ constant, if the concentration of $NO$ is doubled, rate is found to become four times. This shows that,

Rate $\propto[NO]^{2}$

(ii) Keeping $[NO]$ constant, if the concentration of $[O_2]$ is doubled, rate is also found to become double. This shows that,

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Answer**

During an elementary reaction, the number or atoms or ions colliding to react is referred to as molecularity. Had this been an elementary reaction, the order of reaction with respect to $B$ would have been 1 , but in the given rate law it is $\frac{3}{2}$. This indicates that the reaction is not an elementary reaction. Hence, this reaction must be a complex reaction.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Ques.** For a general reaction $A \to B$, plot of concentration of $A$ vs time is given in figure. Answer the following questions on the basis of this graph.

(i) What is the order of the reaction?

(ii) What is the slope of the curve?

(iii) What are the units of rate constant?

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Answer**

A complex reaction occurs through a number of steps i.e., elementary reactions. Number of molecules involved in each elementary reaction may be different, i.e., the molecularity of each step may be different. Therefore, it is meaningless to talk of molecularity of the overall complex reaction.

On the other hand, order of complex reaction depends upon the molecularity of the slowest step. Hence, it is not meaningless to talk of the order of a complex reaction.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Short answer type questions** </Primary>

<hr>

<main>

**Answer**

Balanced chemical equation often leads to incorrect order or rate law. e.g., the following reaction seems to be a tenth order reaction

$
KClO_3+6 FeSO_4+3 H_2 SO_4 \longrightarrow KCl+3 H_2 O+3 Fe_2(SO_4)_3
$

This is actually a second order reaction. Actually the reaction is complex and occurs in several steps. The order of such reaction is determined by the slowest step in the reaction mechanism.

Order is determined experimentally and is confined to the dependence of observed rate of reaction on the concentration of reactants.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

**Ques.** Match the graph given in Column I with the order of reaction given in Column II. More than one item in Column I may link to the same item of Column II.

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>
<footer> <font size = "4">  MCQ (Single correct option)  $\rarr$  MCQ (More than one correct questions)  $\rarr$  Short answer type questions $\rarr$ <span style="color:blue">Matching the columns</span> $\rarr$ Assertion and Reason $\rarr$ Long answer type questions  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

$
[R]=-k t+[R_0]
$

Which denotes a straight line equation similar to $y=m x+c$

On transforming (i) $\quad \frac{[R]-[R_0]}{t}=-k$

$
k=\frac{[R_0]-[R]}{t}
$

Rate $=k \cdot[t]^{0}$

Rate $\propto[t]^{0}$

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

For a first order reaction $\frac{d x}{d t} \propto$ [concentration]

$\therefore$ Graph between rate and concentration may be drawn as

$
\begin{aligned}
k & =\frac{2.303}{t} \log \frac{[R]_0}{[R]} \\\\\\
\frac{k t}{2.303} & =\log [\frac{R^{\circ}}{R}] \\\\\\
\frac{k t}{2.303}= & \log [R]_0-\log [R] \\\\\\
\log [R] & =\underset{\text{ slope }}{(\frac{-k}{2.303}) t}+\underset{\text{ intercept }}{\log [R]_0}
\end{aligned}
$

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

**Ques.** Match the statements given in Column I and Column II.

|  | Column I |  | Column II |
| :---: | :---: | :---: | :---: |
| A. | Catalyst alters the rate of reaction | 1. | Cannot be fraction or zero |
| B. | Molecularity | 2. | Proper orientation is not there |
| C. | Second half-life of first order reaction | 3. | By lowering the activation energy |
| D. | $e^{-E_a / R T}$ | 4. | Is same as the first |
| E. | Energetically favourable reactions are sometimes slow | 5. | Total probability is one |
| F. | Area under the Maxwell, Boltzmann curve is constant | 6. | Refers to the fraction of molecules with energy equal to or greater than activation energy |

</div>

</main>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

1. Catalyst alters the rate of reaction by lowering activation energy.

2. Molecularity can't be fraction or zero. If molecularity is zero, then reaction is not possible.

3. Second half-life of first order reaction is same as first because half-life time is temperature independent.

4. $e^{-E_a / R T}$ refers to the fraction of molecules with kinetic energy equal to or greater than activation energy.

5. Energetically favourable reactions are sometimes slow due to improper orientation of molecule cause some ineffective collision of molecules.

6. Area under the Maxwell, Boltzmann curve is constant because total probability of molecule taking part in a chemical reaction is equal to one.

</div>

</main>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Matching the columns** </Primary>

<hr>

<main>

**Ques.** Match the items of Column I and Column II.

| |Column I |  | Column II |  
| :--- | :--- | :--- | :--- |
| A. | Mathematical expression for rate of reaction | 1. | Rate constant |
| B. | Rate of reaction for zero order reaction is <br> equal to | 2. | Rate law |
| C. |Units of rate constant for zero order reaction <br> is same as that of | 3. | Order of slowest step |  
| D. | Order of a complex reaction is determined by | 4. | Rate of reaction |

</div>

</main>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Assertion and Reason** </Primary>

<hr>

<main>

#### **Assertion** and **Reason**

In the following questions a statement of **Assertion** (A) followed by a statement of **Reason** $(R)$ is given. Choose the correct answer out of the following choices.
 
(a) Both assertion and reason are correct and the reason is correct explanation of assertion.

(b) Both assertion and reason are correct, but reason does not explain assertion.

(d) Both assertion and reason are incorrect.
 
(e) **Assertion** is incorrect, but reason is correct.

</div>

</main>

<hr>

<footer> <font size = "4">  MCQ (Single correct option)  $\rarr$  MCQ (More than one correct questions)  $\rarr$  Short answer type questions $\rarr$  Matching the columns $\rarr$ <span style="color:blue">Assertion and Reason</span> $\rarr$ Long answer type questions  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Assertion and Reason** </Primary>

<hr>

**Answer** (a)

**Assertion** and reason both are correct and reason is the correct explanation of assertion.

Enthalpy of reaction i.e., difference of total enthalpy of reactants and product remains constant in the presence of a catalyst. As a catalyst participating in the reaction forms different activated complex and lowers down the activation energy but the difference in energy of reactant and product remains same.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Assertion and Reason** </Primary>

<hr>

**Answer** (e)

**Assertion** is incorrect, but reason is correct.

Correct assertion is "only effective collision lead to formation of product."

**Reason** defines correct meaning of effective collision, and criterion of collision theory for completion of reaction.

Only those collisions in which molecules have correct orientation and sufficient energy lead to formation of product.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

**Answer**

Only effective collision lead to the formation of products. It means that collisions in which molecules collide with sufficient kinetic energy (called threshold energy = activation energy + energy possessed by reacting species).

And proper orientation lead to a chemical change because it facilitates the breaking of old bonds between (reactant) molecules and formation of the new ones i.e., in products.

e.g., formation of methanol from bromomethane depends upon the orientation of the reactant molecules.

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<footer> <font size = "4">  MCQ (Single correct option)  $\rarr$  MCQ (More than one correct questions)  $\rarr$  Short answer type questions $\rarr$  Matching the columns $\rarr$  Assertion and Reason $\rarr$ <span style="color:blue">Long answer type questions</span>  </font></footer>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

**Answer**

Kinetic energy is directly proportional to the absolute temperature and the number of molecules possessing higher energies increases with increase in temperature, i.e., most probable kinetic energy increases with increase in temperature.

Energy of activation is related to temperature by the following Arrhenius equation

$
k=A e^{-E_a / R T}
$

Thus, it also shows an increase with rise in temperature.

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

**Answer**

A catalyst is a s'ubstance which increases the speed of a reaction without itself undergoing any chemical change.

According to "intermediate complex formation theory" reactants first combine with the catalyst to form an intermediate complex which is short-lived and decomposes to form the products and regenerating the catalyst.

The intermediate formed has much lower potential energy than the intermediate complex formed between the reactants in the absence of the catalyst.

Thus, the presence of catalyst lowers the potential energy barrier and the reaction follows a new alternate pathway which require less activation energy.

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

We know that, lower the activation energy, faster is the reaction because more reactant molecules can cross the energy barrier and change into products.

Enthalpy, $\Delta H$ is a state function. Enthalpy of reaction, i.e., difference in energy between reactants and product is constant, which is clear from potential energy diagram.

Potential energy diagram of catalysed reaction is given as

</div>
<div  style='float: right; width:45%; text-align: left;font-size:21px'>

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

**Answer**

The difference between instantaneous rate of reaction and averatge rate of a reaction are as below

|   | Instantaneous rate of reaction | Average rate of reaction |
| :--- | :--- | :--- |
| (i)| It occurs within  a short span of time |It occurs during a long interval of time. |
|(ii) | It can't be calculated for  multistep reaction |  It can be calculated for multistep reaction |
| (iii)|It can be calculated for elementary reaction. | It can be calculated for elementary reaction. |

</div>

</main>

<hr>

<Success style="float:center; font-size: 25px; text-align:center;"><b> **CHEMICAL KINETICS**</b></Success>

#### <Primary style ="float:center; font-size: 23px; text-align:center;"> **Long answer type questions** </Primary>

<hr>

**Answer**

A reaction in which one reactant is present in large amount and its concentration does not get altered during the course of the reaction, behaves as first order reaction. Such reaction is called pseudo first order reaction.

e.g., (i) hydrolysis of ethyl acetate

$
\begin{matrix} 
\text{ conc. }& CH_3 COOC_2H_5 & + &H_2 O & \xrightarrow{H^{+}} & CH_3 COOH & + & C_2 H_5 OH \\\\\\
\text{Conc.} t= 0 & 0.01 mol & & 10 mol  && 0 mol &  & 0 mol \\\\\\
\text{Conc. at } t & 0 mol & & 9.99 mol  && 0.01 mol &  & 0.01 mol
\end{matrix} 
$

</div>

</main>

<hr>