Problem 87 - Chemistry Matter and Change

Question

Write chemical equations for each of the following decomposition reactions. One or more products might be identified. a. magnesium bromide \(\rightarrow\) b. cobalt (II) oxide \(\rightarrow\) c. titanium (IV) hydroxide \(\rightarrow\) titanium (IV) oxide + water d. barium carbonate \(\rightarrow\) barium oxide \(+\) carbon dioxide

Step-by-Step Solution

Answer

The balanced chemical equations for the decomposition reactions are: a. \[ \text{MgBr}_2 \rightarrow \text{Mg} + \text{Br}_2 \] b. \[ 2\text{CoO} \rightarrow 2\text{Co} + \text{O}_2 \] c. \[ \text{Ti(OH)}_4 \rightarrow \text{TiO}_2 + 2\text{H}_2\text{O} \] d. \[ \text{BaCO}_3 \rightarrow \text{BaO} + \text{CO}_2 \]

Step 1: a. Magnesium bromide decomposition

In this case, we have magnesium bromide (MgBr₂) as the compound undergoing decomposition. When this compound decomposes, it will produce elemental magnesium (Mg) and elemental bromine (Br₂). The balanced equation for this reaction is: \[ \text{MgBr}_2 \rightarrow \text{Mg} + \text{Br}_2 \]

Step 2: b. Cobalt (II) oxide decomposition

For cobalt (II) oxide (CoO), decomposition will result in the formation of elemental cobalt (Co) and elemental oxygen (O₂). The balanced equation for this reaction is: \[ 2\text{CoO} \rightarrow 2\text{Co} + \text{O}_2 \]

Step 3: c. Titanium (IV) hydroxide decomposition

In this situation, we have titanium (IV) hydroxide (Ti(OH)₄) decomposing into titanium (IV) oxide (TiO₂) and water (H₂O). The balanced equation for this reaction is: \[ \text{Ti(OH)}_4 \rightarrow \text{TiO}_2 + 2\text{H}_2\text{O} \]

Step 4: d. Barium carbonate decomposition

For barium carbonate (BaCO₃), decomposition will produce barium oxide (BaO) and carbon dioxide (CO₂). The balanced equation for this reaction is: \[ \text{BaCO}_3 \rightarrow \text{BaO} + \text{CO}_2 \]

Key Concepts

Chemical Equations

When studying chemistry, you'll often need to depict the transformation of reactants to products, and this is where chemical equations come into play. These equations are symbolic representations of chemical reactions, where the reactants are shown on the left-hand side and the products are displayed on the right. For example, the decomposition of magnesium bromide is represented as:

\[\[\begin{align*} \text{MgBr}_2 & \rightarrow \text{Mg} + \text{Br}_2\end{align*}\]\]
It's essential to understand that the compounds and elements are denoted by their chemical symbols, such as Mg for magnesium and Br for bromine. Subscripts, like the '2' in Br₂, tell us the number of atoms involved, while the arrow indicates the direction of the reaction: reactants yield products. To fully understand chemical reactions, you must be comfortable reading and writing these chemical equations.

Balance Chemical Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures the law of conservation of mass is adhered to. This law states that matter cannot be created or destroyed in a chemical reaction. Hence, you must have the same number of atoms for each element on both sides of the equation. Let's take the decomposition of cobalt (II) oxide:

\[\[\begin{align*} 2\text{CoO} & \rightarrow 2\text{Co} + \text{O}_2\end{align*}\]\]
To balance this equation, we needed to ensure that the number of cobalt and oxygen atoms before and after the reaction is equal—resulting in putting a coefficient '2' before cobalt oxide (CoO) and cobalt (Co) on the reactants and products side, respectively. Balancing equations can sometimes be more complex, especially with multiple elements, but the principle remains the same—what goes in must come out, atom for atom.

Types of Chemical Reactions

Chemical reactions are categorized into various types depending on the nature of the process. Decomposition reactions, one of these types, involve a single compound breaking down into two or more simpler substances. The exercises provided earlier are classic examples of decomposition reactions.

For instance, titanium (IV) hydroxide decomposes into titanium (IV) oxide and water:
\[\[\begin{align*} \text{Ti(OH)}_4 & \rightarrow \text{TiO}_2 + 2\text{H}_2\text{O}\end{align*}\]\]
Other types of chemical reactions include synthesis, where two or more substances combine to form one product; single replacement, where one element replaces another in a compound; double replacement, where parts of two compounds swap places to form two new compounds; and combustion, often involving oxygen and producing energy. Each reaction type has its set of patterns and balancing rules. Recognizing the type of reaction can help in predicting products and understanding the reaction's behavior.