Question

At room temperature, the reaction between NO and ${{\rm{O}}_{\rm{2}}}$ to give ${\rm{N}}{{\rm{O}}_{\rm{2}}}$ is fast while that of between CO and ${{\rm{O}}_{\rm{2}}}$ is slow. It is because:

A. The intrinsic energy of the reaction $2NO+O_2\rightleftharpoons 2NO_2$ is less
B. CO is smaller in size that of NO
C. CO is poisonous
D. The activation energy for the reaction $2NO+O_2\rightleftharpoons 2NO_2$

Answer 1

We know that activation energy is the minimum amount of energy that reactants possess to undergo a chemical reaction. Below the activation energy, reactants will not be able to undergo reaction to form products.

Complete step by step answer:

Here, given that, at room temperature reaction between NO and ${{\rm{O}}_{\rm{2}}}$ is fast while that of reaction between CO and ${{\rm{O}}_{\rm{2}}}$ is slow and we have to choose the correct reason for this.

The Arrhenius equation proves the dependence of temperature on the rate of reaction. The Arrhenius equation is,

$k = A{e^{ - Ea/RT}}$

Where, k is rate constant, A is Arrhenius factor, ${E_a}$ is activation energy, R is gas constant and T is temperature.

If we rearrange the Arrhenius equation, we find that,

$k = \dfrac{A}{{{e^{Ea/RT}}}}$

If we increase the value of ${E_a}$, the value of ${e^{Ea/RT}}$ increases and the value of k decreases. That means, if the value of activation energy increases, rate of reaction will decrease and if the activation energy decreases, then the rate of reaction will increase.

Here, reaction of NO and ${{\rm{O}}_{\rm{2}}}$ is fast because of less activation energy of them than CO and ${{\rm{O}}_{\rm{2}}}$.

Hence, option D is the correct answer.

Additional Information:

Collision theory states that for a reaction to occur, the reactant particles must undergo collision with proper energy and orientation. The greater the effective collision between particles, more the rate of chemical reaction is.

Note:
Therefore there are many factors on which the rate of chemical reaction depends, such as, temperature, effect of catalyst, surface area of reactants etc. Rate constant of reaction gets doubled if the temperature rises by 10 degree Celsius. A catalyst speeds up the reaction without getting consumed in the reaction.