Ozone (O₃) in the atmosphere protects against harmful UV radiation. The overall reaction for ozone formation is3O₂ → 2O₃and proceeds in two steps. Step 1 is initiated when molecular oxygen (O₂) absorbs UV light and splits into two oxygen atoms:O₂→ 2OWhich of the following second steps would yield the net reaction for ozone formation?

Question

Quizplus · Accepted Answer

11ecba2d_11be_2020_a3bf_eda1d1080446_MD0008_00 The law of conservation of mass says that in a chemical reaction, atoms are neither created nor destroyed: they can only be rearranged. Therefore, in any chemical reaction the same number of each type of atom must be present on the left and right sides of the reaction arrow. Reactions may proceed in multiple steps, producing intermediates along the way. If the reaction goes to completion (the maximum possible amount of product is formed), all intermediate species must be consumed in subsequent steps to form the final products. In the formation of ozone (O₃), first, one molecule of oxygen (O₂) is split into two oxygen atoms as intermediates (O₂ → 2O). The oxygen atoms are then consumed as each reacts with an oxygen molecule to form ozone. For the reaction to go to completion, the two oxygen atoms must combine with two O₂ molecules to form two ozone molecules (2O + 2O₂→ 2O₃) in the second step. This yields the net reaction 3O₂ → 2O₃. (Choice A) O + O₂ → O₃ correctly shows the reaction of one oxygen atom with one O₂ molecule to form one ozone molecule. However, if this were the second step it would not yield the correct net reaction. Instead, the resulting net reaction would be 2O₂ → O₃ + O. (Choice C) O₂ + 2O → 2O₃ has four oxygen atoms on the left and 6 oxygen atoms on the right, so it is unbalanced. If it were the second step, the resulting net reaction would be 2O₂ → 2O₃, which is also unbalanced. (Choice D) O + 2O₂ → O₃ has five oxygen atoms on the left side and only three on the right, leaving two oxygen atoms unaccounted for. If it were the second step, the resulting net reaction would be 3O₂ → O₃, which is unbalanced. Educational objective: According to the law of conservation of mass, atoms are neither created nor destroyed in a chemical reaction. The same number of each type of atom must be present on both the left and right sides of a reaction arrow. Multistep reactions that go to completion must consume all intermediates produced before or during the final step.

Ozone (O3) in the Atmosphere Protects Against Harmful UV Radiation

Ozone (O₃) in the Atmosphere Protects Against Harmful UV Radiation