# Worksheet on Order of reaction

The sum of powers to which the concentration terms are raised in order to determine the rate of the reaction is known as order of reaction.

There are three orders of reaction:
1. First Order Reaction

2. Second Order Reaction

3. Third Order of reaction

Questions:

1. The rate of the reaction $A + B + C \to \text{Products}$ is given by:

$r = \dfrac{d[A]}{dt} = k[A]^{1/2} [B]^{1/3} [C]^{1/4}$

The order of reaction is:

(a)    1

(b)   3

(c)    5

(d)   13/12

2. Which one of the following statements about the order of a reaction is true?

(a)    The order of a reaction can only be determined by experiment

(b)   The order of a reaction increases with increase in temperature

(c)    A second order reaction is also bimolecular t

(d)   the order of a reaction can be determined from the balanced equation i ( )

3. The second order rate constant is usually expressed as:

(a)    $mole^{-1} \hspace{3mm}litre^{-1} \hspace{3mm} sec^{-1}$

(b)   $mole \hspace{3mm}litre^{-1} \hspace{3mm} sec^{-1}$

(c)    $mole \hspace{3mm}litre \hspace{3mm} sec^{-1}$

(d)   $mole^{-1} litre \hspace{3mm}sec^{-1}$

4. Which of the following is a first order reaction?

(a)    $NH_4NO_2 \to N_2 + 2H_2O$

(b)   $2HI \leftrightharpoons H_2 + I_2$

(c)    $2NO + O_2 \to 2NO_2$

(d)   $2NO_2 \to 2NO + O_2$

5. The rate constant of a reaction is $1.2 \times 10^{-2} mol^{-2} litre^{2} sec^{-1}$. The order of reaction is:

(a)    1

(b)   Zero

(c)    2

(d)   3

6. A reaction involving two different reactants:

(a)    Can never be a bimolecular reaction

(b)   Can never be a first order reaction

(c)     Can never be a unimolecular reaction

(d)   Can never be a second order reaction

7. Order of a reaction is:

(a)    Equal to the sum of the concentration terms in the rate equation

(b)   Equal to the sum of the concentration terms in the stoichiometric

(c)    Always equal to the molecularity of the reaction

(d)   Equal to the sum of the powers of the concentration terms in the rate equation

8. What will be the order of the reaction if doubling the concentration of a reactant increases the rate by a factor of 4 and trebling the concentration of the reactant by a factor of 9?

(a)    Zero order

(b)   First order

(c)    Second order

(d)   Third order

9. The rate of reaction $A + B \to \text{Products}$ is given by the equation $r = k[A][B]$. If B is taken in large excess, the order of the reaction would be:

(a)    0

(b)   1

(c)    2

(d)   Unpredictable

10. The one which is unimolecular reaction is:

(a)    $H_2 + Cl_2 \to 2HCl$

(b)   $H_2O_2 \to H_2O + 1/2O_2$

(c)    $2HCl \to H_2 + Cl$

(d)   $PCl_3 + Cl_2 \to PCl_3$

11. For a given reaction $t_{1/2} = 1/ka^2$. The order of theis reaction is:

(a)    1

(b)   3

(c)    2

(d)   Zero

12. A first order reaction is half-completed in 45 minutes. How long does it need for 99.9% of the reaction to be completed?

(a)    20 hours

(b)   5 hours

(c)    $7 \dfrac{1}{2}$ hours

(d)   10 hours

13. For the first order reaction, half-life is 14s. The time required for the initial concentration to reduce to 1 / 8th of its value is:

(a)    $(14)^3 s$

(b)   42

(c)    28 s

(d)   $(14)^2 s$

14. Which of the following is correct for a first order reaction?

(a)    $t_{1} \propto 1/a$

(b)   $t_{1/2} \propto a$

(c)    $t_{1/2} \propto a^0$

(d)   $t_{1/2} \propto 1/a^2$

15. The rate constant for a first order reaction whose half-life is 480 sec is:

(a)    $1.44 sec^{-1}$

(b)   $1.44 \times 10^{-3} sec^{-1}$

(c)    $0.72 \times 10^{-3} sec^{-1}$

(d)   $2.88 \times 10^{-3} sec^{-1}$

1.(d)    2. (a)     3. (d)     4. (a)     5. (d)

6. (c)     7. (d)     8. (c)    9. (b)     10. (b)

11. (c)     12. (c)     13. (b)     14. (c)     15. (b)

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