Activation Energy

Q.

The thermal decomposition of Acetaldehyde $\left({\mathrm{CH}}_3\mathrm{CHO}\right)$occurs as: ${\mathrm{CH}}_3\mathrm{CHO}\to {\mathrm{CH}}_4+\mathrm{CO}$. The kinetic data of the thermal decomposition is given below. The rate expression thus can be given as:

The kinetic data of the thermal decomposition.

$\left({\mathrm{CH}}_3\mathrm{CHO}\right)$ $\mathbf{mol}\mathbf{.}{\mathbf{lit}}^{\mathbf{-}\mathbf{1}}$	Rate $\mathbf{(}\mathbf{mol}\mathbf{.}{\mathbf{lit}}^{\mathbf{-}\mathbf{1}}\mathbf{.}{\mathbf{sec}}^{\mathbf{-}\mathbf{1}}\mathbf{)}$
$1.75\times {10}^{-3}$	$2.06\times {10}^{-11}$
$3.5\times {10}^{-3}$	$8.24\times {10}^{-11}$
$7.0\times {10}^{-3}$	$3.30\times {10}^{-10}$

1. $\mathrm{k}\left[{\mathrm{CH}}_3\mathrm{CHO}\right]$

2. $\mathrm{k}{\left[{\mathrm{CH}}_3\mathrm{CHO}\right]}^{1/2}$

3. $\mathrm{k}{\left[{\mathrm{CH}}_3\mathrm{CHO}\right]}^2$

4. $\mathrm{k}{\left[{\mathrm{CH}}_3\mathrm{CHO}\right]}^3$

Q. The equilibrium constant kp for the reaction H2g) + CO2, g) gives H2O(g) CO(g) is 4.0 at 1660^° C. Initially0.80 mole H2, and 0.80 mole CO2 are injected into a 5.0 liter flask. What is the equilibrium concentration of co2

Q.

The root mean square speed of a molecule is given as

1. 

2. 

3. 3RT

4. 

Q.

Threshold frequency of metal is $f_0$. When light of frequency $\theta$ = $2f_0$ is incident on the metal plate, velocity of electron emitted in $V_1$. When a frequency of incident radiation is $5f_0.V_2$ is velocity of emitted electron, then $V_1:V_2$ is

1. 1 : 4

2. 1 : 2

3. 2 : 1

4. 4 : 1

Q. what is the n-factor of H2O2 in dispropertionation reaction

Q.

If an endothermic reaction is non-spontaneous at freezing point of water and becomes feasible at its boiling point, then:

1. H and S both are -ve

2. H is +ve, S is -ve

3. H is -ve, S is +ve

4. H and S both are +ve

Q. 98.Why do oxygen and hydrogen molecules (O2 and H2) react to form water molecules even when the octet of these molecules is complete?

Q. Choose the incorrect statement regarding collision theory:

1. For a collision to be effective, orientation of the molecules does not matter.
2. For a collision to be effective, kinetic energy of molecules does matter.
3. The minimum amount of energy the colliding molecules must possess to participate in a chemical reaction is the threshold energy.
4. Kinetic energy and orientation factor both play an important role for an effective collision to take place

Q.

When two substances (reactants) react to give products reversibly, the reaction quotient (Q) of the reaction as the reaction proceeds

1. becomes zero.

2. decreases with time till equilibrium point.

3. increases with time till equilibrium point.

4. remains the same.

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.

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. At 473 K, equilibrium constant $K_c$ for decomposition of phosphorus pentachloride, ${PCl}_5$ is $8.3\times {10}^{-3}$. If decomposition is depicted as,
${PCl}_5\left(g\right)\rightleftharpoons {PCl}_3\left(g\right)+{Cl}_2\left(g\right)$ ${\Delta }_r{H}^{\ominus }=124.0kJ{mol}^{-1}$
(a) Write an expression for $K_c$ for the reaction.
(b) What is the value of $K_c$ for the reverse reaction at the same temperature?
(c) What would be the effect on $K_c$ if (i) more ${PCl}_5$ is added (ii) pressure is increased (iii) the temperature is increased ?

Q. Select the correct diagram for an endothermic reaction that proceeds through two steps, where the second step is rate determining:

1. 
2. 
3. 
4. 

Q. Lindemann proposed the following detailed mechanism for gas phase isomerization, the reaction is

In the above scheme, $A^{\ast }$ is a molecule that has enough vibrational energy to decompose or isomerise. The Lindemann mechanism is followed by most of gas phase decomposition or isomerization reaction.
For the overall unimolecular isomerization of cyclopropane to propylene at , the values of versus concentration is as follows.
$\underset{K_{unit}}{\left|M\right|}\underset{\frac{1}{137.5}}{\left|1M\right|}\underset{\frac{1}{131.25}{\text{in s}}^{-1}}{\left|2M\right|}$

If with the increase in temperature the overall rate increases, then the correct representation at a very high concentration of M is

1. 
2. 
3. 
4. 

Q. For the chemical process, graph of energy and progress of reaction are plotted.

Which of the following is correct?

1. It is the exothermic reaction, $\Delta H=b-a$
2. Threshold energy, $e=a+c$
3. $(E_a{)}_f<(E_a{)}_b$
4. All of the above.

Q. For the chemical process, graph of energy and progress of reaction are plotted.

Which of the following is correct?

1. It is the exothermic reaction, $\Delta H=b-a$
2. Threshold energy, $e=a+c$
3. $(E_a{)}_f<(E_a{)}_b$
4. All of the above.

Q. Write the industrial / commercial method of preparation of dihydrogen with equations.

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