Problem 88 - General Chemistry: Principles and Modern Applications

Question

Complete and balance the following. Write the simplest equation possible. If no reaction occurs, so state. (a) \(\operatorname{Li}_{2} \mathrm{CO}_{3}(\mathrm{s}) \stackrel{\Delta}{\longrightarrow}\) (b) \(\mathrm{CaCO}_{3}(\mathrm{s})+\mathrm{HCl}(\mathrm{aq}) \longrightarrow\) (c) \(\mathrm{Al}(\mathrm{s})+\mathrm{NaOH}(\mathrm{aq}) \longrightarrow\) (d) \(\operatorname{BaO}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(1) \longrightarrow\) (e) \(\mathrm{Na}_{2} \mathrm{O}_{2}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{g}) \longrightarrow\)

Step-by-Step Solution

Answer

The balanced equations are: (a) \(Li_2CO_3 \stackrel{\Delta}{\longrightarrow} Li_2O + CO_2\), (b) \(CaCO_3 + 2HCl \longrightarrow CaCl_2 + H_2O + CO_2\), (c) \(2Al + 2NaOH + 6H_2O \longrightarrow 2Na[Al(OH)_4]\), (d) \(BaO + H_2O \longrightarrow Ba(OH)_2\), (e) \(2Na_2O_2 + 2CO_2 \longrightarrow 2Na_2CO_3 + O_2\).

Step 1: Identify The Type of Reaction and The Possible Chemical Products

Looking at the reactants, we can identify the type of the reaction and potential products. By following established chemistry rules, it is possible to predict the products for each reaction. For example, a salt (like lithium carbonate) when exposed to heat (indicated by the delta symbol) generally undergoes decomposition, resulting in the formation of a metal oxide and carbon dioxide. The application of such reasoning would generate potential chemical products for each reaction.

Step 2: Write The Unbalanced Chemical Equation

After predicting the products, write down the chemical reaction using the formula of these products. In each equation, the reactants will yield the predicted products.

Step 3: Balance The Chemical Equation

Each equation must follow the Law of Conservation of Mass, meaning the number of atoms of each element must be the same on both the reactant and product sides of the equation. This step requires making sure that the equation is balanced by adjusting the coefficients in front of the chemical formulas.

Step 4: Repeat The Process for Each Reaction

Repeat these steps for each of the chemical reactions mentioned in the exercise (a to e).

Key Concepts

Decomposition Reactions

Decomposition reactions are a fundamental type of chemical reaction where a single compound breaks down into two or more simpler substances. This process is triggered by energy input, such as heat, light, or electricity. For instance, heating lithium carbonate ( Li_{2}CO_{3}) causes it to decompose into lithium oxide ( Li_{2}O) and carbon dioxide ( CO_{2}).
In decomposition reactions, recognizing what the starting compound will yield as it breaks down is key. For example:

• While breaking down ionic compounds such as carbonates, a metal oxide and carbon dioxide are often the decomposition products.
• Heating hydrates typically results in the release of water and an anhydrous compound.

By understanding the common patterns, it becomes easier to predict what a decomposition reaction will produce.

Law of Conservation of Mass

The law of conservation of mass is a fundamental principle of chemistry that states mass is neither created nor destroyed in a chemical reaction. In practical terms, it implies that the total mass of reactants must equal the total mass of products.
This law is crucial during chemical reactions as it ensures that equations are accurately balanced. When balancing chemical equations, each element must have the same number of atoms on both sides of the equation.
For example, if the chemical equation begins with 2 atoms of oxygen in the reactants, it must have 2 atoms of oxygen in the products as well.

• Mass remains consistent before and after chemical transformations.
• Balancing requires adjustment of coefficients but not changes to the chemical formulas.

Applying this principle helps in accurately predicting and understanding the outcome of chemical reactions.

Chemical Equation Balancing

Balancing chemical equations is a critical skill in chemistry that involves adjusting the coefficients in front of each compound to ensure the same number of atoms of each element exist on both sides. This step is crucial to honor the law of conservation of mass.
Understanding the steps for balancing can make the process easier:

• Identify each compound within the equation and list all elements present.
• Count the number of atoms of each element in both reactants and products.
• Adjust coefficients to balance the number of atoms for each element.
• Repeat the process iteratively until balanced.

Balancing ensures that the reaction is not only correct but also accurately represents the conservation of matter. It's like solving a puzzle where all pieces must fit perfectly.

Product Prediction in Chemical Reactions

Predicting the products of a chemical reaction is an essential skill for chemists. Understanding the nature of reactants and the type of reaction involved helps in predicting what substances will be formed.
There are a few guidelines that can aid in this process:

• Identify the type of reaction: Decomposition, synthesis, single or double replacement, etc.
• Recognize patterns of known reactions, like metal carbonates generally decomposing to yield metal oxides and CO_{2}.
• Use tables or rules for solubility and reactivity to foresee possible outcomes in replacement reactions.

Accurate prediction requires comprehension of chemical behavior and familiarity with the types of reactions. This understanding allows chemists to predict outcomes logically and without memorization for each specific scenario.