Nitric Oxide and Ozone Reaction | NO + O3
Nitric oxide (NO) reacts with ozone (O3) to produce nitrogen dioxide (NO'2) and oxygen gas (O2). This reaction is a redox reaction and also an elementary reaction.
In this tutorial you will learn followings.
- Explanation of nitric oxide (NO) and ozone (O3) reaction
- Balanced chemical equation
- Kinetics of reaction
NO + O3 = NO2 + O2
Colourless nitric oxide reacts with ozone gas to produce nitrogen dioxide and oxygen gas. In this reaction, all reactants and products are gases. Also, this reaction is a redo reaction (oxidation - reduction reaction) because oxidation numbers of nitrogen atom and oxygen atom are changed.
This reaction involves to ozone layer depletion in the Earth's stratosphere. This is a big environmental problem.
Balanced Equation
NO + O3 = NO2 + O2
Reaction is already balanced. No need to do furthermore studies to balance the reaction. One mole of NO reacts with one mol of O3 and produce one mol of NO2 and one mol of O2.
Balanced reaction with physical states
All NO, O3, NO2 and O2 are in gaseous states.
NO(g) + O3(g) = NO2(g) + O2(g)
Reaction kinetics
Reaction of NO and O3 is an elementary reaction. Therefore, this reaction is a one of the rare reaction of elementary reactions.
What is an elementary reaction?
An elementary reaction is a chemical reaction in which one or more chemical species react directly to form products in a single reaction step and with a single transition state.
Heat of reaction, entropy change, free energy of reaction
Here, we are going to see heat of reaction, entropy change, free energy of reaction of NO + O3 reaction.
- Heat of reaction = -199.74 kJ mol-1
- Entropy change = - 4.49 J/K
- Free energy of reaction = -198.45 kJ mol-1
Because free energy of reaction is negative, this reaction is spontaneous.
Safety of NO + O3 reaction
Ozone is a very toxic gas to humans and plants in ground level though it protects us from UV rays coming from sun.
Where NO reacts with ozone and describe the procedure
Due to human activities, nitrogen dioxide gas was released to the atmosphere. This nitrogen dioxide molecules absorbs energy from sunlight and dissociates to nitric oxide and oxygen gas. These NO radicals are very active and reacts with ozone molecules. This is what happens in the ozone layer due the human activities of nitrogen dioxide emissions.
References
- The rate constant of NO + O3 → NO2 + O2 in the temperature range of 283–443 K
- Chemistry of Ozone Formation
Questions asked by students.
O3 oxidation
In this reaction nitric oxide (NO) os oxidized to nitrogen dioxide (NO2). Therefore ozone (O3) should be reduced. But, actually it does not happen. in the O3 molecule, one oxygen atom is at -1 oxidation state. To understand this correctly, we have to find the mechanism of the NO + O3 reacction.
Is NO + O3 → NO2 + O2 an elementary reaction? How do you wtite the rate equation?
Yes. NO + O3 → NO2 + O2 is an elementary reaction.
Reaction rate = K[NO(g)][O3], K = reaction rate constant
