Question

There are fears that the protective ozone layer around the earth is being depleted. Ozone, \(\mathrm{O}_{3}\), is produced by the interaction of ordinary oxygen gas in the atmosphere with ultraviolet light and lightning discharges. The oxides of nitrogen (which are common in automobile exhaust gases), in particular, are known to decompose ozone. For example, gaseous nitric oxide (NO) reacts with ozone gas to produce nitrogen dioxide gas and oxygen gas. Write the unbalanced chemical equation for this process.

Short answer

The balanced chemical equation for the reaction between gaseous nitric oxide (NO) and ozone gas (O3) to produce nitrogen dioxide gas (NO2) and oxygen gas (O2) is: \(2\text{NO} + 2\text{O}_{3} \rightarrow 2\text{NO}_{2} + 3\text{O}_{2}\).

Step-by-step solution

Identify the reactants and products

The problem states that the reaction involves gaseous nitric oxide (NO) and ozone gas (O3) as reactants and produces nitrogen dioxide gas (NO2) and oxygen gas (O2) as products.

Write the unbalanced chemical equation

In this step, we'll write down the reactants and products using their chemical symbols and combine them to form the unbalanced chemical equation: NO + O3 → NO2 + O2

Balance the chemical equation

To balance the chemical equation, we need to make sure the number of atoms for each element is equal on both sides of the equation. For the current unbalanced equation: NO + O3 → NO2 + O2 - Nitrogen atoms: There is 1 nitrogen atom on both sides (balanced) - Oxygen atoms: There are 3 oxygen atoms on the left and 4 oxygen atoms on the right (unbalanced) To balance the oxygen atoms, you can multiply the O3 molecule on the left by 2, the NO molecule on the left by 2, and the O2 molecule on the right by 3. 2NO + 2O3 → 2NO2 + 3O2 Now the equation is balanced: - Nitrogen atoms: 2 nitrogen atoms on both sides - Oxygen atoms: 6 oxygen atoms on both sides

Key concepts

Ozone Layer Depletion

The ozone layer, a fragile shield of gas, protects the Earth from the harmful portion of the rays of the sun, thus helping preserve life on the planet. Ozone depletion refers to the thinning and reduced concentration of the ozone layer, primarily caused by human-made chemicals, like chlorofluorocarbons (CFCs), halons, and other substances collectively known as ozone-depleting substances (ODS).

When ODS reach the stratosphere, they are exposed to UV rays, causing them to release chlorine and bromine atoms, which then lead to the destruction of ozone molecules. This process is concerning because it increases the amount of UV radiation that reaches the Earth's surface, leading to increased skin cancers, cataract incidences, and potential harm to ecosystems.

A specific example of a chemical reaction contributing to ozone layer depletion is given in the exercise. Gaseous nitric oxide (NO), a byproduct of internal combustion engines, reacts with ozone (O3) to yield nitrogen dioxide (NO2) and molecular oxygen (O2), thereby reducing the total ozone.

Chemical Reactions

Chemical reactions involve the transformation of one or more substances into different substances. The substances that undergo the reaction are known as reactants, and the new substances produced are known as products.

Several signs indicate a chemical reaction, including color changes, temperature changes, gas formation, and precipitate formation. In the case of the ozone depletion example, the reactants are nitric oxide (NO) and ozone (O3), while the products are nitrogen dioxide (NO2) and oxygen gas (O2).

The reaction showcased in this exercise is a type of decomposition reaction, where ozone molecules are broken down. Understanding these basic types of reactions helps students predict and balance reactions in more complex scenarios. Chemical reactions are represented by chemical equations that need to be balanced to obey the law of conservation of mass, which states that mass cannot be created or destroyed in a chemical reaction.

Stoichiometry

Stoichiometry is the quantitative relationship between reactants and products in a chemical reaction. It involves using balanced chemical equations to calculate the quantities of reactants needed or products formed. A balanced chemical equation has equal numbers of each type of atom on both sides, adhering to the law of conservation of mass.

To balance the given equation in the exercise (NO + O3 → NO2 + O2), we ensure that there are equal numbers of nitrogen and oxygen atoms on both sides of the equation. By employing stoichiometric coefficients (the numbers placed before the chemical formulas), the atoms are balanced, providing a crucial stepping stone towards calculations in chemical reactions.

Stoichiometry is not only about balancing chemical equations but also involves mole ratios, molar mass, and gas laws, which are all part of converting between quantities (like mass, volume, and number of particles) of reactants and products in chemical reactions.