Problem 83 - Chemistry: The Central Science

Question

Write a balanced equation for the reaction of each of the following compounds with water: (a) \(\mathrm{SO}_{2}(g)\), (b) \(\mathrm{Cl}_{2} \mathrm{O}_{7}(g)\), (c) \(\mathrm{Na}_{2} \mathrm{O}_{2}(s)\), (d) \(\mathrm{BaC}_{2}\) (s), (e) \(\mathrm{RbO}_{2}\) (s) (f) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(s)\), (g) \(\mathrm{NaH}(\) s).

Step-by-Step Solution

Answer

(a) \(\mathrm{SO}_{2}(g) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{H}_{2}\mathrm{SO}_{3}(aq)\) (b) \(\mathrm{Cl}_{2}\mathrm{O}_{7}(g) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{HClO}_{4}(aq)\) (c) \(\mathrm{Na}_{2}\mathrm{O}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{NaOH}(aq) + \mathrm{H}_{2}\mathrm{O}_{2}(aq)\) (d) \(\mathrm{BaC}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{Ba(OH)}_{2}(aq) + \mathrm{C}_{2}\mathrm{H}_{2}(g)\) (e) \(\mathrm{RbO}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{RbOH}(aq) + \mathrm{H}_{2}\mathrm{O}_{2}(l)\) (f) \(\mathrm{Mg}_{3}\mathrm{N}_{2}(s) + 6 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 3 \, \mathrm{Mg(OH)}_{2}(s) + 2 \, \mathrm{NH}_{3}(g)\) (g) \(\mathrm{NaH}(s) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{NaOH}(aq) + \mathrm{H}_{2}(g)\)

Step 1: Identify the type of reaction

This is an acid-base reaction, as sulfur dioxide dissolves in water to form an acidic solution.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{SO}_{2}(g) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{H}_{2}\mathrm{SO}_{3}(aq)\) (b) Reaction of \(\mathrm{Cl}_{2}\mathrm{O}_{7}(g)\) with water

Step 1: Identify the type of reaction

This is an acid-base reaction, where chlorine heptoxide reacts with water to form an acidic solution.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{Cl}_{2}\mathrm{O}_{7}(g) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{HClO}_{4}(aq)\) (c) Reaction of \(\mathrm{Na}_{2}\mathrm{O}_{2}(s)\) with water

Step 1: Identify the type of reaction

This is an acid-base reaction, as sodium peroxide reacts with water to form an alkaline solution.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{Na}_{2}\mathrm{O}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{NaOH}(aq) + \mathrm{H}_{2}\mathrm{O}_{2}(aq)\) (d) Reaction of \(\mathrm{BaC}_{2}(s)\) with water

Step 1: Identify the type of reaction

This is a hydrolysis reaction, where water reacts with barium carbide to produce calcium hydroxide and acetylene gas.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{BaC}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{Ba(OH)}_{2}(aq) + \mathrm{C}_{2}\mathrm{H}_{2}(g)\) (e) Reaction of \(\mathrm{RbO}_{2}(s)\) with water

Step 1: Identify the type of reaction

This is an acid-base reaction, as rubidium superoxide reacts with water to form alkali and hydrogen peroxide.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{RbO}_{2}(s) + 2 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 2 \, \mathrm{RbOH}(aq) + \mathrm{H}_{2}\mathrm{O}_{2}(l)\) (f) Reaction of \(\mathrm{Mg}_{3}\mathrm{N}_{2}(s)\) with water

Step 1: Identify the type of reaction

This is a hydrolysis reaction, where magnesium nitride reacts with water to produce magnesium hydroxide and ammonia.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{Mg}_{3}\mathrm{N}_{2}(s) + 6 \, \mathrm{H}_{2}\mathrm{O}(l) \rightarrow 3 \, \mathrm{Mg(OH)}_{2}(s) + 2 \, \mathrm{NH}_{3}(g)\) (g) Reaction of \(\mathrm{NaH}(s)\) with water

Step 1: Identify the type of reaction

This is an acid-base reaction, as sodium hydride reacts with water to produce sodium hydroxide and hydrogen gas.

Step 2: Write the balanced equation

The balanced chemical equation is: \(\mathrm{NaH}(s) + \mathrm{H}_{2}\mathrm{O}(l) \rightarrow \mathrm{NaOH}(aq) + \mathrm{H}_{2}(g)\)

Key Concepts

Balanced Chemical Equations

In chemistry, a balanced chemical equation is crucially important as it depicts the conservation of mass and the quantity of each substance involved in a reaction. This means that the number of atoms of each element is the same on both the reactant and product sides of the equation. Balancing chemical equations ensures the Law of Conservation of Mass is respected, implying that matter is neither created nor destroyed during a chemical reaction.

For instance, when we examine the reaction between sodium peroxide (\(\mathrm{Na}_2\mathrm{O}_2(s)\)) and water (\(\mathrm{H}_2\mathrm{O}(l)\)), the balanced equation is:
\(\mathrm{Na}_2\mathrm{O}_2(s) + 2\, \mathrm{H}_2\mathrm{O}(l) \rightarrow 2\, \mathrm{NaOH}(aq) + \mathrm{H}_2\mathrm{O}_2(aq)\).

• All elements have the same number of atoms on each side of the equation: Sodium (Na), oxygen (O), and hydrogen (H).
• This balanced equation shows the substances in the reaction accurately reflects their real-world interactions.

Balancing equations is crucial for predicting the amounts of products formed in a reaction as well as the amount of reactants required.

Acid-Base Reactions

Acid-base reactions are fundamental to chemistry and involve the transfer of protons (H⁺ ions) between substances. In these reactions, an acid typically donates a proton to a base. This is well represented in reactions like that of sulfur dioxide (\(\mathrm{SO}_2(g)\)) reacting with water (\(\mathrm{H}_2\mathrm{O}(l)\)). In this reaction, sulfur dioxide, the acid, produces sulfurous acid (\(\mathrm{H}_2\mathrm{SO}_3(aq)\)) when combined with water.

Here are some key points about acid-base reactions:

• The strength of an acid or base can affect the extent of the reaction and the concentration of products.
• Indicators are often used to determine the pH of a solution resulting from an acid-base reaction.
• Acid-base reactions lead to the formation of water and salt as common products, though there are exceptions.

The reaction transforms neutral water into a solution with distinct acidic or basic properties, which can be tested and observed in practical laboratory scenarios.

Hydrolysis Reactions

Hydrolysis reactions involve the chemical breakdown of a compound due to its reaction with water. These reactions play significant roles in organic and inorganic chemistry, breaking down complex molecules into simpler components.

A classic example is the reaction of magnesium nitride (\(\mathrm{Mg}_3\mathrm{N}_2(s)\)) with water, which produces magnesium hydroxide (\(\mathrm{Mg(OH)}_2\)) and ammonia (\(\mathrm{NH}_3\)) gas. This exemplifies how hydrolysis can alter the chemical structure of the reacting compounds:

• These reactions help in breaking down larger molecules into smaller, more manageable substances.
• They are crucial in numerous biological processes, including digestion and metabolism.
• Hydrolysis is crucial for understanding weathering processes in geology and soil chemistry.

Through hydrolysis, we gain insight into the adaptability and reactivity of molecules in various environments, which is critical for applications in chemical engineering and environmental science.