Activation Energy

Q.

When water is added to quicklime rise in temperature is observed. This is an example of _____ reaction

Q. For a reaction $A\to B$, enthalpy of reaction is $–4.2kJmo{l}^{–1}$ and enthalpy of activation is $9.6kJmo{l}^{–1}$. The correct potential energy profile for the reaction is shown in option.

1. 
   
   
2. 
   
   
3. 
   
4. 
   

Q.

What is activation energy ?How it is calculated?

Q.

Define the average rate of reaction?

Q. Most effective coagulating ion for the coagulation of TiO₂ sol is

TiO₂ सॉल के स्कंदन के लिए सर्वाधिक प्रभावी स्कंदनकारी आयन है

1. Na⁺
2. F^–
3. Al³⁺
4. $P{O}_4^{3-}$

Q.

What is the drawback of Collision Theory?

Q.

What is the difference between zero-order and first-order kinetics?

Q.

Three beakers labelled as A, B and C each containing $25\mathrm{mL}$ of water were taken. A small amount of $\mathrm{NaOH}$, anhydrous${\mathrm{CuSO}}_4$ and were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers A and B, whereas, in the case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is(are) correct? $\left(\mathrm{i}\right)$ In beakers A and B, the exothermic process has occurred.

$\left(\mathrm{ii}\right)$ In beakers A and B, the endothermic process has occurred.

$\left(\mathrm{iii}\right)$ In beaker C exothermic process has occurred.

$\left(\mathrm{iv}\right)$ In beaker C endothermic process has occurred.

1. $\left(\mathrm{i}\right)\mathrm{only}$

2. $\left(\mathrm{ii}\right)\mathrm{only}$

3. $\left(\mathrm{i}\right)\mathrm{and}\left(\mathrm{iv}\right)$

4. $\left(\mathrm{ii}\right)\mathrm{and}\left(\mathrm{iii}\right)$

Q.

The given reaction of $\mathrm{Ba}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+2{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{s}\right)$ is endothermic/exothermic?

Q.

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

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

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

Q.

The rate of a reaction quadruples when the temperature changes from 293 K to 313 K. Calculate the energy of activation of the reaction assuming that it does not change with temperature.

Q.

For the reaction 2NO + Br2 ------> 2NOBr Mechanism given is NO +Br2 <------> NOBr, (fast) NOBr2 + NO ------> 2NOBr (slow) Then which of the following is true? (1) Order of the above reaction is less than molecularity of reaction (2) Order of the above reaction is equal to molecularity of reaction (3) Order is greater than molecularity of reaction (4) Relation between order and molecularity cannot be predicted

Q. The forward and backward activation energy of exothermic reaction $A\to B$ is $80\text{and}280kJmo{l}^{-1}$ respectively. The enthalpy change of the forward reaction $A\to B$ ( in $kJ/mol$) will be :

1. -200
2. -360
3. -280
4. -80

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. The activation energy of one of the reaction in a biochemical process is $532611Jmo{l}^{-1}$. When the temperature falls from $310K$ to $300K$, the change in rate constant observed is $k_{300}=x\times {10}^{-3}{k}_{310}$. The value of $x$ is
[Given: $In10=2.3,R=8.3J{K}^{-1}{\text{mol}}^{-1}$]

Q.

When the temperature is raised from $27\mathrm{to}42°\mathrm{C}$, there are five times as many molecules with energy above the reaction threshold. Its activation energy is _______ $\mathrm{J}/\mathrm{mol}$. $\left(\mathrm{R}=8.314\mathrm{J}{\mathrm{mol}}^{-1}{\mathrm{K}}^{-1},\mathrm{Take}\ln 5=1.6094\right)$

Q. For first order parallel reaction $k_1$ and $k_2$ are $4$ and $2mi{n}^{-1}$ respectively at $300K$. The activation energies for the formation of $B$ and $C$ are $30,000$ and $38,314J/mol$ respectively. The temperature at which $B$ and $C$ will be obtained in equimolar ratio is:

1. $757.48K$
2. $378.74K$
3. $600K$
4. None of these

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. At room temperature the rms speed of the molecules of certain diatomic gas is found to be 1930m/s.the gas is 1.hydrogen. 2.fluorine. 3.oxygen 4. Chlorine.

Q.

Why does every chemical reaction require a certain amount of activation energy?

Q.

What happens to most probable kinetic energy and the energy of activation with increases in temperature?

Q. Equimolar conc. of H2 and I2 are heated to equilibrium in a 2l flask. At equilibrium the forward and backward rate constants are found to be equal. What percent of initial conc. of H2 has reacted at equilibrium?

Q. The speed of three molecules is 2m/s, 3m/s, 4m/s.find the average speed and rms speed of the molecules

Q.

While cooking, if the bottom of the vessel is getting blackened on the outside, it means that

1. the food is not cooked completely.

2. the fuel is not burning completely.

3. the fuel is wet.

4. the fuel is burning completely.

Q.

Which of the following graphs represents exothermic reaction ?

(a) Only I
(b) Only II
(c) Only III
(d) I and II

Q. Different possible thermal decomposition pathways for peroxyesters are shown below. Match each pathway from Column I with an appropriate structure from Column II and select the correct answer using the code given below the lists.

1. P -3 Q - 2 R - 1 S - 4
2. P -4 Q - 1 R - 2 S - 3
3. P -2 Q -4 R - 3 S - 1
4. P -1 Q - 3 R - 4 S - 2

Q.

Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of one example.

Q. $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right);\Delta H=-22kcal$
Activation energy, $E_a$ for the given reaction is $70kcal$. Find the activation energy for $2N{H}_3\left(g\right)\to N_2\left(g\right)+3H_2\left(g\right)$ in $kcal$.

Q. What is the activation energy for a reaction whose rate constant doubles when temperature changes from ${30}^{\circ }C\text{to}{40}^{\circ }C$?

1. $72.56{\text{KJ mol}}^{-1}$
2. $45.45{\text{KJ mol}}^{-1}$
3. $54.5{\text{KJ mol}}^{-1}$
4. None of these

Q.

Oxygen is available in plenty in the air yet fuels do not burn by themselves at room temperature. Explain.