Chemical Kinetics - Result Question 13

####14. Consider the given plots for a reaction obeying Arrhenius equation $\left(0^{\circ} C<T<300^{\circ} C\right)$ : ( $k$ and $E _a$ are rate constant and activation energy, respectively)

(2019 Main, 10 Jan I)

Choose the correct option.

(a) Both I and II are wrong

(b) Both I and II are correct

(c) I is wrong but II is right

(d) I is right but II is wrong

15 For the reaction, $2 A+B \longrightarrow$ products

When concentration of both $(A$ and $B$ ) becomes double, then rate of reaction increases from $0.3 mol L^{-1} s^{-1}$ to $2.4 mol L^{-1} s^{-1}$.

When concentration of only $A$ is doubled, the rate of reaction increases from $0.3 mol L^{-1} s^{-1}$ to $0.6 mol L^{-1} s^{-1}$.

Which of the following is true?

(2019 Main, 9 Jan II)

(a) The whole reaction is of 4 th order

(b) The order of reaction w.r.t. $B$ is one

(c) The order of reaction w.r.t. $B$ is 2

(d) The order of reaction w.r.t. $A$ is 2

16 The following results were obtained during kinetic studies of the reaction;

(2019 Main, 9 Jan I)

$2 A+B \longrightarrow$ Products
Experiment $[\boldsymbol{A}]$
(in $\left.mol L^{-1}\right)$
$[\boldsymbol{B}]$
(in $\left.mol L^{-1}\right)$
Initial rate of
reaction
(in $\left.mol L^{-1} min^{-1}\right)$
I. 0.10 0.20 $6.93 \times 10^{-3}$
II. 0.10 0.25 $6.93 \times 10^{-3}$
III. 0.20 0.30 $1.386 \times 10^{-2}$

The time (in minutes) required to consume half of $A$ is

(a) 5

(b) 10

(c) 100

(d) 1

Show Answer

Answer:

Correct Answer: 14. (d)

Solution:

  1. The Arrhenius equation is,

$$ k=A \cdot e^{-E _a / R T} $$

where, $k=$ rate constant,

$$ A=\text { Arrhenius constant }, E _a=\text { activation energy, } $$

and $T=$ temperature in $K$

From the equation, it is clear that $k$ decreases exponentially with $E _a$. So, the plot-I is correct.

In the plot-II, $k$ is plotted with temperature (in ${ }^{\circ} C$ but not in $K$ ). So, at $0^{\circ} C, k \neq 0$ and $k$ will increase exponentially with temperature upto $300^{\circ} C$. Therefore, the plot-II is also correct.



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