Activation Energy

Q. An exothermic chemical reaction proceeds by two stages:
$\text{Reactants}\stackrel{\text{stage 1}}{\to }\text{Intermediate}\stackrel{\text{stage 2}}{\to }\text{Products}$
The activation energy of stage 1 is $50\text{kJ/mol}$. The overall enthalpy change of the reaction is $-100\text{kJ/mol}$. Which diagram could represent the energy level diagram for the other reaction.

1. 
2. 
3. 
4. 

Q. A reaction having equal energies of activation for forward and reverse reactions has

1. $\Delta H=0$
2. $\Delta H=\Delta G=\Delta S=0$
3. $\Delta G=0$
4. $\Delta S=0$

Q.

For an endothermic reaction, energy of activation is $E_a$ and enthalpy of reaction is $\Delta H$ (both of these in kJ/mol). Minimum value of $E_a$ will be:

1. Less than $\Delta H$

2. Equal to $\Delta H$

3. More than $\Delta H$

4. Equal to zero

Q.

The activation energy of a reaction can be determined from the slope of which of the following graphs?

1. ln K vs T
2. $\frac{T}{lnK}vs\frac{l}{T}$
3. $\frac{lnK}{T}vsT$
4. ln K vs $\frac{1}{T}$

Q.

The rate of a reaction doubles when its temperature changes form 300 K to 310 K. Activation energy of such a reaction will be $(R=8.314J{K}^{-1}mo{l}^{-1}andlog2=0.301)$

1. $53.6kjmo{l}^{-1}$

2. $48.6kjmo{l}^{-1}$

3. $58.5kjmo{l}^{-1}$

4. $60.5kjmo{l}^{-1}$

Q. The activation energy for a simple chemical reaction, $A\to B$ is $E_a$ in forward direction. The activation energy for reverse reaction.
[CBSE AIPMT 2003]

1. Can be less than or more than $E_a$
2. Is always double of $E_a$
3. Is negative of $E_a$
4. Is always less than $E_a$

Q. For a first order reaction, A $\to$ P, the temperature (T) dependent rate constant (k) was found to follow the equation:
$logk=\frac{2000}{T}+6.0$
the pre - exponential factor A and the activation energy $E_{\alpha }$. respectively, are:

1. $6.0s^{-1}and16.6kJmo{l}^{-1}$
2. $1.0\times {10}^6{s}^{-1}and9.2kJmo{l}^{-1}$
3. $1.0\times {10}^6{s}^{-1}and16.6kJmo{l}^{-1}$
4. $1.0\times {10}^6{s}^{-1}and38.3kJmo{l}^{-1}$

Q.

In an exothermic reaction $A\to B$, the activation energy of reverse reaction is twice that of forward reaction. If enthalpy of the reaction is -80 kJ $mo{l}^{-1}$, the activation energy of the reverse reaction is :

1. $80.0kJmo{l}^{-1}$

2. $60.0kJmo{l}^{-1}$

3. $40.0kJmo{l}^{-1}$

4. $160.0kJmo{l}^{-1}$

Q.

The activation energies for the forward and reverse elementary reactions in the system $A\rightleftharpoons B$ are 10.303 and 8.000 k cal respectively at 500K. Assuming the pre-exponential factor to be the same for both the forward and reverse steps and R = 2 cal $K^{-1}mo{l}^{-1}$, calculate equilibrium constant of the reaction :

1. 0.1

2. 1.00

3. 10.0

4. 100

Q. Select the correct statement regarding activation energy:

1. Activation energy may be greater than the heat of a reaction
2. Activation energy is less than the threshold energy
3. Rate of reaction is inversely proportional to activation energy
4. All of these