Problem 16 - Chemistry The Central Science In Si Units

Question

Write balanced chemical equations to correspond to each of the following descriptions: (a) When sulfur trioxide gas reacts with water, a solution of sulfuric acid forms. (b) Boron sulfide, \(\mathrm{B}_{2} \mathrm{~S}_{3}(s),\) reacts violently with water to form dissolved boric acid, \(\mathrm{H}_{3} \mathrm{BO}_{3},\) and hydrogen sulfide gas. (c) Phosphine, \(\mathrm{PH}_{3}(g)\), combusts in oxygen gas to form water vapor and solid tetraphosphorus decaoxide. (d) When solid mercury(II) nitrate is heated, it decomposes to form solid mercury(II) oxide, gaseous nitrogen dioxide, and oxygen. (e) Copper metal reacts with hot concentrated sulfuric acid solution to form aqueous copper(II) sulfate, sulfur dioxide gas, and water.

Step-by-Step Solution

Answer

(a) \(\text{SO}_3\left( g \right) + \text{H}_2\text{O}\left( l \right) \rightarrow \text{H}_2\text{SO}_4\left( aq \right)\); (b) \(\text{B}_2\text{S}_3\left( s \right) + 6\text{H}_2\text{O}\left( l \right) \rightarrow 2\text{H}_3\text{BO}_3\left( aq \right) + 3\text{H}_2\text{S}\left( g \right)\); (c) \(4\text{PH}_3\left( g \right) + 8\text{O}_2\left( g \right) \rightarrow 6\text{H}_2\text{O}\left( g \right) + \text{P}_4\text{O}_{10}\left( s \right)\); (d) \(2\text{Hg}\left(\text{NO}_3\right)_2\left( s \right) \rightarrow 2\text{HgO}\left( s \right) + 4\text{NO}_2\left( g \right) + \text{O}_2\left( g \right)\); (e) \(\text{Cu}\left( s \right) + 2\text{H}_2\text{SO}_4\left( l \right) \rightarrow \text{CuSO}_4\left( aq \right) + \text{SO}_2\left( g \right) + 2\text{H}_2\text{O}\left( l \right)\).

Step 1: Analyze the Reaction Description for Part (a)

In part (a), sulfur trioxide gas (\(\text{SO}_3\left( g \right)\)) reacts with water (\(\text{H}_2\text{O}\left( l \right)\)) to form sulfuric acid (\(\text{H}_2\text{SO}_4\left( aq \right)\)). This is a direct combination reaction where the reactants combine to form the product: \(\text{SO}_3\left( g \right) + \text{H}_2\text{O}\left( l \right) \rightarrow \text{H}_2\text{SO}_4\left( aq \right)\).

Step 2: Analyze the Reaction Description for Part (b)

In part (b), boron sulfide (\(\text{B}_2\text{S}_3\left( s \right)\)) reacts with water (\(\text{H}_2\text{O}\left( l \right)\)) to produce boric acid (\(\text{H}_3\text{BO}_3\left( aq \right)\)) and hydrogen sulfide gas (\(\text{H}_2\text{S}\left( g \right)\)). The balanced chemical equation is: \(\text{B}_2\text{S}_3\left( s \right) + 6\text{H}_2\text{O}\left( l \right) \rightarrow 2\text{H}_3\text{BO}_3\left( aq \right) + 3\text{H}_2\text{S}\left( g \right)\).

Step 3: Analyze the Reaction Description for Part (c)

Phosphine gas (\(\text{PH}_3\left( g \right)\)) burns in oxygen gas (\(\text{O}_2\left( g \right)\)) to form water vapor (\(\text{H}_2\text{O}\left( g \right)\)) and solid tetraphosphorus decaoxide (\(\text{P}_4\text{O}_{10}\left( s \right)\)). The balanced equation is: \(4\text{PH}_3\left( g \right) + 8\text{O}_2\left( g \right) \rightarrow 6\text{H}_2\text{O}\left( g \right) + \text{P}_4\text{O}_{10}\left( s \right)\).

Step 4: Analyze the Reaction Description for Part (d)

Upon heating, mercury(II) nitrate (\(\text{Hg}\left(\text{NO}_3\right)_2\left( s \right)\)) decomposes to form mercury(II) oxide (\(\text{HgO}\left( s \right)\)), nitrogen dioxide (\(\text{NO}_2\left( g \right)\)), and oxygen (\(\text{O}_2\left( g \right)\)). The balanced equation for this decomposition is: \(2\text{Hg}\left(\text{NO}_3\right)_2\left( s \right) \rightarrow 2\text{HgO}\left( s \right) + 4\text{NO}_2\left( g \right) + \text{O}_2\left( g \right)\).

Step 5: Analyze the Reaction Description for Part (e)

Copper metal (\(\text{Cu}\left( s \right)\)) reacts with hot concentrated sulfuric acid (\(\text{H}_2\text{SO}_4\left( l \right)\)) to form copper(II) sulfate (\(\text{CuSO}_4\left( aq \right)\)), sulfur dioxide (\(\text{SO}_2\left( g \right)\)), and water (\(\text{H}_2\text{O}\left( l \right)\)). The balanced equation is: \(\text{Cu}\left( s \right) + 2\text{H}_2\text{SO}_4\left( l \right) \rightarrow \text{CuSO}_4\left( aq \right) + \text{SO}_2\left( g \right) + 2\text{H}_2\text{O}\left( l \right)\).

Key Concepts

Combination Reactions

A combination reaction is when two or more reactants join to form a single product. This often occurs with elements or simple compounds coming together to create more complex substances. For example, when sulfur trioxide \(\text{SO}_3(g)\) reacts with water \(\text{H}_2\text{O}(l)\) to form sulfuric acid \(\text{H}_2\text{SO}_4(aq)\), we witness an elegant combination:

• Sulfur trioxide and water, both individual entities, merge into one comprehensive compound: sulfuric acid.
• This reaction highlights the simplicity and beauty of composition reactions, where simplicity breeds complexity.

Combination reactions are foundational in chemistry because they demonstrate how new, more complex substances are created from simpler components. They are particularly important in forming various compounds we come into contact with daily.
Consider this the primary dance of chemistry: two become one!

Decomposition Reactions

Decomposition reactions are the opposite of combination reactions. In these reactions, a single compound breaks down into two or more simpler products. One good example is how mercury(II) nitrate \(\text{Hg}(\text{NO}_3)_2(s)\) decomposes when heated:

• The compound splits into mercury(II) oxide \(\text{HgO}(s)\), nitrogen dioxide \(\text{NO}_2(g)\), and oxygen \(\text{O}_2(g)\).
• Energy, often in the form of heat, is typically needed to drive decomposition.

Decomposition reactions are critical to understanding the stability and breakdown of compounds. Think of these reactions as the unraveling of a complex puzzle and revealing all its intricate pieces.
They help us understand processes such as fermentation, respiration, and even the digestion of food.

Combustion Reactions

Combustion reactions are the fireworks of chemical reactions. They occur when a substance combines with oxygen, releasing energy in the form of light or heat. A perfect illustration is phosphine \(\text{PH}_3(g)\) combusting in oxygen \(\text{O}_2(g)\) to form water vapor \(\text{H}_2\text{O}(g)\) and solid tetraphosphorus decaoxide \(\text{P}_4\text{O}_{10}(s)\):

• These reactions are highly exothermic, meaning they produce significant amounts of energy.
• Combustion is central to many everyday processes, such as car engines running and campfires burning.

Understanding combustion is crucial for energy-related applications.
They are not just about fire; they are about how we harness energy from various fuels.

Chemical Reaction Analysis

Analyzing chemical reactions involves breaking down the components and understanding how they interact. It's like being a detective in a mysterious story of atoms and molecules. This analysis uses balanced chemical equations, which provide a roadmap of the reactants and products involved.

• A balanced equation follows the law of conservation of mass, ensuring the quantity of each element remains constant before and after the reaction.
• By balancing equations, we accurately depict what happens in a chemical transformation.

For example, examining the reaction of copper with hot concentrated sulfuric acid reveals the production of copper(II) sulfate, sulfur dioxide gas, and water.
Each element's count must match on both sides of the equation. By understanding these equations, we gain insight into crucial industrial processes and environmental impacts.
Analyzing these reactions comprehensively helps propel innovations across various fields of science and technology.