Problem 34 - Introductory Chemistry Atoms First

Question

John writes the chemical equation \(\mathrm{O}_{2}+\mathrm{O}_{2} \rightarrow 1 \frac{1}{3} \mathrm{O}_{3}\). Sue claims that is not a chemical reaction because there is no chemical change, saying "Oxygen is on both sides of the arrow!" (Hint: \(\mathrm{O}_{2}\) is oxygen that you breathe; \(\mathrm{O}_{3}\) is ozone, which is quite toxic.) Sue also says it's not balanced. Which of Sue's complaints is correct? Explain.

Step-by-Step Solution

Answer

Sue's claim regarding no chemical change is incorrect, as oxygen molecules (\(\mathrm{O}_{2}\)) are converted into a new substance, ozone (\(\mathrm{O}_{3}\)). Her claim about the equation being unbalanced is also incorrect, since both sides have an equal number of oxygen atoms (4).

Step 1: Identify reactants and products

The given chemical equation is: \[\mathrm{O}_{2}+\mathrm{O}_{2} \rightarrow \frac{4}{3} \mathrm{O}_{3}\] Reactants are the substances present on the left side of the arrow, that participate in the chemical reaction. In this case, the reactants are two molecules of oxygen gas (\(\mathrm{O}_{2}\), which we breathe). The product is the substance formed as a result of the reaction, present on the right side of the arrow. Here, the product is ozone gas (\(\mathrm{O}_{3}\), which is toxic).

Step 2: Evaluate the claim that there is no chemical change

Sue claims that there is no chemical change because she observes oxygen on both sides of the arrow. However, oxygen exists in different forms, depending on the number of oxygen atoms bonded. In this case, we have two oxygen molecules (\(\mathrm{O}_{2}\)) on the reactant side and ozone (\(\mathrm{O}_{3}\)) as the product. The reactants and products are chemically different even though they share the same element - oxygen. Thus, there is a chemical change taking place as oxygen molecules are converted into a new substance, ozone. Sue's claim about no chemical change is incorrect.

Step 3: Check the equation for balance

To determine if the reaction is balanced, we must count the number of atoms of each element on both sides of the equation. For this equation, we should look at the number of oxygen atoms. On the left side (reactants) of the equation we have: 2 \(\mathrm{O}_{2}\) molecules, each containing 2 oxygen atoms, thus, a total of 2 * 2 = 4 oxygen atoms. On the right side (products) of the equation we have: \(\frac{4}{3} \mathrm{O}_{3}\) molecules, each molecule contains 3 oxygen atoms, thus, a total of \(\frac{4}{3} * 3 = 4\) oxygen atoms. Both sides of the equation have an equal number of oxygen atoms, which means that the equation is balanced. Sue's claim that the equation is not balanced is incorrect. In conclusion, Sue's claim about no chemical change is incorrect because there is a conversion of oxygen molecules (\(\mathrm{O}_{2}\)) to ozone (\(\mathrm{O}_{3}\)). However, her claim about the equation being unbalanced is also incorrect as both sides of the equation contain an equal number of oxygen atoms.

Key Concepts

Balancing Chemical Equations

Balancing chemical equations ensures that the number of each type of atom is the same on both sides of the equation. This is crucial because it reflects the law of conservation of mass, where matter cannot be created or destroyed in a chemical reaction.

To balance a chemical equation, we count the number of atoms of each element in the reactants and products. If they don't match, coefficients are adjusted to achieve balance. In the given exercise:

• The left side has oxygen molecules, (\(2 \mathrm{O}_{2}\)), contributing 4 oxygen atoms.
• The right side forms (\(\frac{4}{3} \mathrm{O}_{3}\)), which also accounts for 4 oxygen atoms.

This demonstrates that both sides are balanced, satisfying Sue's concern about balance. Ensure counting is accurate to maintain the integrity of the equation.

Reactants and Products

In a chemical reaction, reactants are substances that start a reaction, while products are new substances formed. They are separated by an arrow in chemical equations, with reactants on the left and products on the right.

In this specific case:

• **Reactants:** Oxygen gas, (\(\mathrm{O}_{2}\)), is breathable and harmless in regulated amounts.
• **Products:** Ozone, (\(\mathrm{O}_{3}\)), which is more reactive and toxic.

Even though both reactants and products here involve oxygen, they are different molecules with distinct properties and structures. This indicates a chemical change occurred, converting oxygen gas into ozone.

Types of Chemical Reactions

Chemical reactions can be classified into various types such as synthesis, decomposition, single-replacement, and double-replacement based on how reactants transform into products.

The exercise depicts a synthesizing reaction:

• Synthesis Reaction: This is when simpler substances combine to form a more complex compound. Here, oxygen molecules (\(\mathrm{O}_{2}\)) combine to form ozone (\(\mathrm{O}_{3}\)).

Recognizing the type of reaction helps predict products and understand the process involved. This reaction illustrates how changes at the molecular level can lead to significant differences in the chemical properties of the materials formed.