# Activation Energy worksheet

Activation energy was introduced by Swedish scientist Svante Arrhenius in 1889. The minimum energy which is required inorder to start a chemical reaction is known as Activation energy. The unit of activation energy is Kilojoules per mole and denoted by Ea.

Questions:

1. The Arrhenius equation expressing the effect temperature on the rate constant of the reaction is:

(a)    $K = \dfrac{Ea}{RT}$

(b)   $K = e^{-Ea/RT}$

(c)    $K = \log_e \dfrac{Ea}{RT}$

(d)   $K = Ae^{-Ea/RT}$

2. In Arrhenius plot, intercept is equal to:

(a)    ln K

(b)   ln A

(c)    –Ea/R

(d)   $\log_{10}a$

3. Velocity constant of a reaction at 290 K was found to be $3.2 \times 10^{-3}$. At 300 K it will be:

(a)    $9.6 \times 10^{-3}$

(b)   $1.28 \times 10^{-2}$

(c)    $6.4 \times 10^{-3}$

(d)   $3.2 \times 10^{-4}$

4. An endothermic reaction $A \to B$ has an activation energy of 15 kcal/ mole and the energy of reaction is 5 kcal/ mole. The activation energy for the reaction $B \to A$ is:

(a)    15 kcal/mole

(b)   20 kcl/mole

(c)    10 kcl/mole

(d)   zeri

5. The activation energy of a reaction is 9 kcal / mole. The increase in the rate constant when its temperature is raised from 295 to 300 K is approximately:

(a)    50 %

(b)   100 %

(c)    10 %

(d)   25 %

6. A graph plotted between $\log K vs 1/T$ for calculating activation energy is shown by:

Activation energy

7. When the increase the temperature, the rate of reaction increases because of:

(a)    more number of collisions

(b)   more number of energetic electrons

(c)    less number of energetic electrons

(d)   decrease in mean free path

8. According to the Arrhenius equation a straight line is to be obtained by plotting the logarithm of the rate constant of a chemical reaction (log k) against:

(a)    T

(b)   $\log 1/T$

(c)    1/T

(d)   $\log T$

9. An example of photochemical reaction is:

(a)    darkening of silver chloride in light

(b)   rusting of iron in moist air

(c)    glowing of charcoal

(d)   blackening of white lead upon prolonged  exposure to air

10. In photochemical reactions:

(a)    temperature may have a little effect in certain cases

(b)   temperature has the same effect as on thermal reactions

(c)    temperature has no effect

(d)   temperature has opposite effect as on thermal reactions

11. The reaction occurring in a glow-worm is most correctly refered as:

(a)    a photochemical reaction

(b)   It start the reaction

(c)    a simple chemical reaction

(d)   chemiluminescence

12. Which is not true about a catalyst?

(a)    It changes rate of reaction by changing activation energy

(b)   It is more effective in powder form

(c)    It start the reaction

(d)   Its mass and composition do not change during the reaction

13. Vision is a:

(a)    Chemical reaction

(b)   Photochemical reaction

(c)    No reaction

(d)   Can not be said

14. The value of quantum efficiency for HBr in comparison to HCI is:

(a)    Equal

(b)   Greater

(c)    Less

(d)   Can not be predicted

15. Fluorescence is shown by:

(a)    ZnS

(b)   $CaF_2$

(c)    Both

(d)   None of these

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

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

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

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