Problem 69 - Chemistry Matter and Change

Question

Write skeleton equations for these reactions. $$\begin{array}{c}{\text { a. butane }\left(\mathrm{C}_{4} \mathrm{H}_{10}\right)(1)+\text { oxygen }(\mathrm{g}) \rightarrow} \\ {\text { carbon dioxide }(\mathrm{g})+\text { water }(1)}\end{array}$$ $$\begin{array}{c}{\text { b. aluminum carbonate(s) } \rightarrow} \\ {\text { aluminum oxide }(s)+\text { carbon dioxide }(g)}\end{array}$$ $$\begin{array}{c}{\text { c. silver nitrate }(a q)+\text { sodium sulfide }(a q) \rightarrow} \\ {\text { silver sulfide }(s)+\text { sodium nitrate }(a q)}\end{array}$$

Step-by-Step Solution

Answer

(a) \(\mathrm{C}_{4}\mathrm{H}_{10} (1) + \mathrm{O}_{2} (g) \rightarrow \mathrm{CO}_{2} (g) + \mathrm{H}_{2}\mathrm{O} (1)\); (b) \(\mathrm{Al}_{2}(\mathrm{CO}_{3})_{3} (s) \rightarrow \mathrm{Al}_{2}\mathrm{O}_{3}(s) +\mathrm{CO}_{2}(g)\); (c) \(\mathrm{AgNO}_{3}(aq) + \mathrm{Na}_{2}\mathrm{S}(aq) \rightarrow \mathrm{Ag}_{2}\mathrm{S}(s) + \mathrm{NaNO}_{3}(aq)\).

Step 1: Identify Reactants and Products for Reaction (a)

In reaction (a), the reactants are butane, \( \mathrm{C}_{4} \mathrm{H}_{10} \ (1) \) , and oxygen, \( \mathrm{O}_{2} \ (g) \) . The products are carbon dioxide, \( \mathrm{CO}_{2} \ (g) \) and water, \( \mathrm{H}_{2} \mathrm{O} \ (1) \) . Begin by writing the unbalanced chemical equation: \( \mathrm{C}_{4} \mathrm{H}_{10} (1) + \mathrm{O}_{2} (g) \rightarrow \mathrm{CO}_{2} (g) + \mathrm{H}_{2} \mathrm{O} (1) \) .

Step 2: Write Skeleton Equation for Reaction (b)

For reaction (b), the reactant is aluminum carbonate, \( \mathrm{Al}_{2}(\mathrm{CO}_{3})_{3}(s) \) , and the products are aluminum oxide, \( \mathrm{Al}_{2}\mathrm{O}_{3}(s) \) and carbon dioxide, \( \mathrm{CO}_{2}(g) \) . Construct the unbalanced skeleton equation as follows: \( \mathrm{Al}_{2}(\mathrm{CO}_{3})_{3} (s) \rightarrow \mathrm{Al}_{2}\mathrm{O}_{3}(s) +\mathrm{CO}_{2}(g) \) .

Step 3: Construct Skeleton Equation for Reaction (c)

In reaction (c), the reactants are silver nitrate, \( \mathrm{AgNO}_{3}(aq) \) and sodium sulfide, \( \mathrm{Na}_{2}\mathrm{S}(aq) \) . The products are silver sulfide, \( \mathrm{Ag}_{2}\mathrm{S}(s) \) and sodium nitrate, \( \mathrm{NaNO}_{3}(aq) \) . Write the skeleton equation as: \( \mathrm{AgNO}_{3}(aq) + \mathrm{Na}_{2}\mathrm{S}(aq) \rightarrow \mathrm{Ag}_{2}\mathrm{S}(s) + \mathrm{NaNO}_{3}(aq) \) .

Key Concepts

Chemical Reactions

Chemical reactions serve as the backbone of chemistry and represent the transformation of substances. In these processes, reactants are converted into products through the breaking and forming of chemical bonds. A chemical reaction is typically represented by a chemical equation. This equation not only shows the reactants and products but also the relative quantities of substances involved.

Understanding chemical reactions involves recognizing the following key elements:

• Reactants: Substances that undergo change.
• Products: Substances that are formed from the reaction.
• Chemical Bonds: Forces holding atoms together, which break and reform during reactions.
• Reaction Conditions: Factors like temperature, pressure, and catalysts that can affect the outcome.

At the core, every chemical reaction follows the law of conservation of mass – meaning the mass of reactants equals the mass of products, thus ensuring that atoms are neither created nor destroyed in the process.

Writing skeleton equations is a vital skill that helps depict the transformation from reactants to products, emphasizing the qualitative aspect of a reaction without initially detailing stoichiometry or balancing atom counts.

Butane Combustion

Butane combustion is a type of chemical reaction known as combustion, where a substance (butane in this case) reacts with oxygen to produce heat and often light.

The primary products of hydrocarbon combustion are carbon dioxide and water. This kind of reaction is highly exothermic, meaning it releases energy. For butane ({\( \mathrm{C}_{4}\mathrm{H}_{10} \)}), the reaction with oxygen can be represented by the skeleton equation:
\[\mathrm{C}_{4}\mathrm{H}_{10} (1) + \mathrm{O}_{2} (g) \rightarrow \mathrm{CO}_{2} (g) + \mathrm{H}_{2} \mathrm{O} (1)\]
This equation shows:

• The reactants: Butane ({\( \mathrm{C}_{4}\mathrm{H}_{10} \)}) and Oxygen ({\( \mathrm{O}_{2} \)}).
• The products: Carbon dioxide ({\( \mathrm{CO}_{2} \)}) and Water ({\( \mathrm{H}_{2}\mathrm{O} \)}).

It's important to understand that while this skeleton equation sets up the scenario, balancing the equation is necessary to respect the law of conservation of mass, ensuring the equation reflects the same number of each type of atom on both sides.

Aluminum Carbonate Decomposition

The decomposition of aluminum carbonate is a type of chemical reaction where a single compound breaks into two or more simpler substances.

For aluminum carbonate, this decomposition occurs as follows:
\[\mathrm{Al}_{2}(\mathrm{CO}_{3})_{3}(s) \rightarrow \mathrm{Al}_{2}\mathrm{O}_{3}(s) + \mathrm{CO}_{2}(g)\]
Here's what happens in this decomposition reaction:

• The reactant: Aluminum carbonate ({\( \mathrm{Al}_{2}(\mathrm{CO}_{3})_{3} \)}) is a compound prone to breaking down under certain conditions.
• The products: Aluminum oxide ({\( \mathrm{Al}_{2}\mathrm{O}_{3} \)}) and Carbon dioxide ({\( \mathrm{CO}_{2} \)}).

Decomposition reactions like this are essential in various applications, from industrial production of materials to understanding geochemical processes.

Silver Nitrate Reaction

The reaction involving silver nitrate is an example of a double displacement reaction.

In these kinds of reactions, the ions in the reactants exchange partners, resulting in the formation of new products. The skeleton equation for the reaction between silver nitrate and sodium sulfide is:
\[\mathrm{AgNO}_{3}(aq) + \mathrm{Na}_{2}\mathrm{S}(aq) \rightarrow \mathrm{Ag}_{2}\mathrm{S}(s) + \mathrm{NaNO}_{3}(aq)\]
Breaking this down:

• Reactants: Silver nitrate ({\( \mathrm{AgNO}_{3} \)}) and sodium sulfide ({\( \mathrm{Na}_{2}\mathrm{S} \)}), both initially in aqueous form.
• Products: Silver sulfide ({\( \mathrm{Ag}_{2}\mathrm{S} \)}), which often precipitates out of the solution, and sodium nitrate ({\( \mathrm{NaNO}_{3} \)}) which remains in solution.

Double displacement reactions are noteworthy for their ability to produce precipitates, gases, or weak electrolytes, and they play a critical role in fields such as medicinal chemistry and environmental science.