Problem 69 - Chemistry Matter and Change

Question

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

Step-by-Step Solution

Answer

For the given reactions, the skeleton equations are as follows: a. \(C_4H_{10} + O_2 \rightarrow CO_2 + H_2O\) b. \(Al_2(CO_3)_3 (s) \rightarrow Al_2O_3 (s) + CO_2 (g)\) c. \(AgNO_3 (aq) + Na_2S (aq) \rightarrow Ag_2S (s) + NaNO_3 (aq)\)

Step 1: 1. Reaction A: Butane and Oxygen

For this reaction, butane (C4H10) reacts with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O). The skeleton equation for this reaction can be written as: C4H10 + O2 -> CO2 + H2O

Step 2: 2. Reaction B: Aluminum Carbonate Decomposition

For this reaction, aluminum carbonate (Al2(CO3)3) decomposes into aluminum oxide (Al2O3) and carbon dioxide (CO2). The skeleton equation for this reaction can be written as: Al2(CO3)3 (s) -> Al2O3 (s) + CO2 (g)

Step 3: 3. Reaction C: Silver Nitrate and Sodium Sulfide

For this reaction, silver nitrate (AgNO3) reacts with sodium sulfide (Na2S) to produce silver sulfide (Ag2S) and sodium nitrate (NaNO3). The skeleton equation for this reaction can be written as: AgNO3 (aq) + Na2S (aq) -> Ag2S (s) + NaNO3 (aq)

Key Concepts

Skeleton Equations

In the realm of chemical reactions, skeleton equations play a crucial role. They provide a basic representation of the reactants and products involved without necessarily indicating the quantities needed to balance the equation.

• A skeleton equation uses chemical formulas to present the substances participating in the reaction.
• It does not include coefficients, which are used to balance the equation.
• The equation essentially answers "what" reacts, rather than "how much" reacts.

For example, in exercise A, the reaction involves butane and oxygen forming carbon dioxide and water. The skeleton equation is:\[\text{C}_4\text{H}_{10} + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\]This equation shows the reactants and products, setting the stage for further balancing.

Combustion Reaction

The combustion reaction is a type of chemical reaction where a substance combines with oxygen, releasing energy.

• It typically involves hydrocarbons or organic molecules.
• The usual products are carbon dioxide and water.
• Combustion reactions are exothermic, meaning they release heat.

Exercise A outlines a combustion reaction involving butane \((\text{C}_4\text{H}_{10})\) and oxygen. The skeleton equation for a combustion reaction is a good starting point to understand the larger concept, focusing on how hydrocarbons interact with oxygen to form carbon dioxide and water. The skeleton equation given can be expanded upon by balancing to reflect the conservation of mass and energy.

Decomposition Reaction

A decomposition reaction involves a single compound breaking down into two or more simpler substances. It's one of the primary types of chemical reactions that helps to form new substances from a single source.

• Involves only one reactant and multiple products.
• Energy input is often required to initiate the reaction, such as heat, light, or electricity.

In exercise B, aluminum carbonate is decomposing into aluminum oxide and carbon dioxide. The skeleton equation is:\[\text{Al}_2(\text{CO}_3)_3 (s) \rightarrow \text{Al}_2\text{O}_3 (s) + \text{CO}_2 (g)\]This exemplifies a decomposition reaction as one compound splits into separate substances. Balancing this equation is essential for illustrating the conservation of mass.

Precipitation Reaction

A precipitation reaction occurs when two solutions combine to form an insoluble solid, known as a precipitate. This type of reaction is crucial for many chemical processes, as it helps in identifying and isolating specific compounds.

• Involves ionic compounds in aqueous solutions.
• One of the products is a solid, which falls out of the solution.

In exercise C, the reaction between silver nitrate and sodium sulfide results in the formation of silver sulfide, a solid precipitate, and sodium nitrate, which remains in solution. The skeleton equation is:\[\text{AgNO}_3 (aq) + \text{Na}_2\text{S} (aq) \rightarrow \text{Ag}_2\text{S} (s) + \text{NaNO}_3 (aq)\]This reaction highlights the formation of a precipitate, which can often be identified when the reaction mixture becomes cloudy. Balancing the equation confirms that matter is neither created nor destroyed.