Problem 9 - Chemistry Matter and Change

Question

Apply Hydrogen peroxide \(\left(\mathrm{H}_{2} \mathrm{O}_{2}\right)\) decomposes to produce water and oxygen. Write a balanced chemical equation for this reaction, and determine the possible mole ratios.

Step-by-Step Solution

Answer

The balanced equation is \(\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2\). The mole ratios are 1:2 for \(\mathrm{H}_2\mathrm{O}_2\) to \(\mathrm{H}_2\mathrm{O}\) and 1:1 for \(\mathrm{H}_2\mathrm{O}_2\) to \(\mathrm{O}_2\).

Step 1: Write the Unbalanced Equation

The chemical formula for hydrogen peroxide is \(\mathrm{H}_{2} \mathrm{O}_{2}\). When it decomposes, it produces water \(\mathrm{H}_2\mathrm{O}\) and oxygen gas \(\mathrm{O}_2\). Initially, write the unbalanced chemical equation: \[ \mathrm{H}_{2} \mathrm{O}_{2} \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{O}_2 \].

Step 2: Write and Count the Atoms

Count the number of each type of atom on both sides of the equation. On the left, there are 2 hydrogen atoms and 2 oxygen atoms. On the right, there are 2 hydrogen atoms and 3 oxygen atoms (2 from \(\mathrm{O}_2\) and 1 from \(\mathrm{H}_2\mathrm{O}\)).

Step 3: Balance the Equation

To balance the equation, we need to make the number of oxygen atoms equal on both sides. You can start by putting a 2 in front of \(\mathrm{H}_2\mathrm{O}\) to balance hydrogen atoms: \[ \mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2 \]. Now, there are 2 hydrogen atoms on each side and 4 oxygen atoms on both sides, maintaining the same number of each type of atom.

Step 4: Determine Mole Ratios

From the balanced reaction \(\mathrm{H}_2\mathrm{O}_2 \rightarrow 2\mathrm{H}_2\mathrm{O} + \mathrm{O}_2\), mole ratios can be derived: 1 mole of \(\mathrm{H}_2\mathrm{O}_2\) produces 2 moles of \(\mathrm{H}_2\mathrm{O}\) and 1 mole of \(\mathrm{O}_2\). So, the possible mole ratios are 1:2 for \(\mathrm{H}_2\mathrm{O}_2\) to \(\mathrm{H}_2\mathrm{O}\) and 1:1 for \(\mathrm{H}_2\mathrm{O}_2\) to \(\mathrm{O}_2\).

Key Concepts

Balancing Chemical Equations

Balancing chemical equations is like solving a puzzle—ensuring that the number of each type of atom is the same on both sides of the equation. When hydrogen peroxide (\( \mathrm{H}_{2} \mathrm{O}_{2} \)) decomposes, it forms water and oxygen. The unbalanced equation starts as: \( \mathrm{H}_{2}\mathrm{O}_{2} \rightarrow \mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2} \).### How to BalanceFirstly, count the atoms: - On the left, there are 2 hydrogens and 2 oxygens. - On the right, there are 2 hydrogens and 3 oxygens. Since the oxygen is unbalanced, adding coefficients helps balance the equation. We add a 2 in front of water:\( \mathrm{H}_{2}\mathrm{O}_{2} \rightarrow 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2} \). This fix makes the atom count equal, balancing the equation and illustrating the law of conservation of mass—no atoms are lost; they’re just rearranged. Balancing equations teaches us that chemical reactions must adhere to basic physical laws, preparing us for more complex chemistry later on! ### Tips for Success:- Always start by writing the unbalanced equation. - Recount atoms after adjusting coefficients. - Keep practising to make it second nature.

Mole Ratios

Mole ratios come into play once the equation is balanced. They show the proportional relationships between reactants and products in a chemical reaction. In the decomposition of hydrogen peroxide: \( \mathrm{H}_{2}\mathrm{O}_{2} \rightarrow 2\mathrm{H}_{2}\mathrm{O} + \mathrm{O}_{2} \),the ratio provides a clear guide to how much of each substance is involved. ### Determining Mole RatiosFrom the balanced equation: - 1 mole of \( \mathrm{H}_{2} \mathrm{O}_{2} \) yields 2 moles of \( \mathrm{H}_{2} \mathrm{O} \) and 1 mole of \( \mathrm{O}_{2} \). This means that if you start with 5 moles of \( \mathrm{H}_{2} \mathrm{O}_{2} \), you will get 10 moles of \( \mathrm{H}_{2} \mathrm{O} \) and 5 moles of \( \mathrm{O}_{2} \). Understanding mole ratios is crucial in chemistry because they help us:- Predict how much of a reactant is needed or a product is formed.- Convert between mass, volume, and particles. These ratios provide a practical tool for scaling chemical reactions in the lab and industry.

Decomposition Reaction

A decomposition reaction is a type of chemical reaction where a single compound breaks down into two or more simpler substances. In the given problem, hydrogen peroxide (\( \mathrm{H}_2\mathrm{O}_2 \)) decomposes into water (\( \mathrm{H}_2\mathrm{O} \)) and oxygen (\( \mathrm{O}_2 \)). This can be seen in the equation:\[\mathrm{H}_2\mathrm{O}_2 \rightarrow \mathrm{H}_2\mathrm{O} + \mathrm{O}_2 \].### Characteristics of Decomposition Reactions- **Single Reactant**: Typically, they start with one complex molecule.- **Multiple Products**: They tend to yield two or more simpler products.- **Energy Requirement**: Often need energy, like heat, light, or electricity, to occur. In our example, hydrogen peroxide naturally decomposes to relieve its inherent instability, releasing oxygen gas—a central reason \( \mathrm{H}_2\mathrm{O}_2 \) is used as a bleach and disinfectant. Understanding decomposition reactions is key in fields such as environmental science and engineering, where these reactions play a role in processes like the breakdown of pollutants. Getting a grasp on these concepts strengthens your understanding of chemical changes at a molecular level. Embrace these reactions as they underline the transformative nature of chemistry—unveiling how complex compounds can simplify into basic substances.