Problem 86 - 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) \(\mathrm{Cl}_{2} \mathrm{O}_{7}(\mathrm{~g})\), (c) \(\mathrm{Na}_{2} \mathrm{O}_{2}(s)\), (d) \(\mathrm{BaC}_{2}(\mathrm{~s})\), (e) \(\mathrm{RbO}_{2}(s)\), (f) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(\mathrm{~s})\), (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) \( \mathrm{Cl}_{2} \mathrm{O}_{7}(g) + \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{HC}\mathrm{lO}_{4}(aq) \) (c) \( \mathrm{Na}_{2} \mathrm{O}_{2}(s) + 2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{NaOH}(aq) + \mathrm{O}_{2}(g) \) (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) \( \mathrm{RbO}_{2}(s) + 2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{RbOH}(aq) + \mathrm{O}_{2}(g) \) (f) \( \mathrm{Mg}_{3} \mathrm{N}_{2}(s) + 6 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 3 \mathrm{Mg(OH)}_{2}(aq) + 2 \mathrm{NH}_{3}(g) \) (g) \( \mathrm{NaH}(s) + \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{NaOH}(aq) + \mathrm{H}_{2}(g) \)

Step 1: (a) Reaction of SO2 with water

When sulfur dioxide (SO2) reacts with water (H2O), the product formed is sulfurous acid (H2SO3). The balanced chemical equation for this reaction is: \( \mathrm{SO}_{2}(g) + \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{H}_{2} \mathrm{SO}_{3}(aq) \)

Step 2: (b) Reaction of Cl2O7 with water

When dichlorine heptoxide (Cl2O7) reacts with water (H2O), the product formed is perchloric acid (HClO4). The balanced chemical equation for this reaction is: \( \mathrm{Cl}_{2} \mathrm{O}_{7}(g) + \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{HC}\mathrm{lO}_{4}(aq) \)

Step 3: (c) Reaction of Na2O2 with water

When sodium peroxide (Na2O2) reacts with water (H2O), the products formed are sodium hydroxide (NaOH) and oxygen gas (O2). The balanced chemical equation for this reaction is: \( \mathrm{Na}_{2} \mathrm{O}_{2}(s) + 2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{NaOH}(aq) + \mathrm{O}_{2}(g) \)

Step 4: (d) Reaction of BaC2 with water

When barium carbide (BaC2) reacts with water (H2O), the products formed are barium hydroxide (Ba(OH)2) and acetylene (C2H2). The balanced chemical equation for this reaction is: \( \mathrm{BaC}_{2}(s) + 2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{Ba(OH)}_{2}(aq) + \mathrm{C}_{2} \mathrm{H}_{2}(g) \)

Step 5: (e) Reaction of RbO2 with water

When rubidium superoxide (RbO2) reacts with water (H2O), the products formed are rubidium hydroxide (RbOH) and oxygen gas (O2). The balanced chemical equation for this reaction is: \( \mathrm{RbO}_{2}(s) + 2 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 2 \mathrm{RbOH}(aq) + \mathrm{O}_{2}(g) \)

Step 6: (f) Reaction of Mg3N2 with water

When magnesium nitride (Mg3N2) reacts with water (H2O), the products formed are magnesium hydroxide (Mg(OH)2) and ammonia gas (NH3). The balanced chemical equation for this reaction is: \( \mathrm{Mg}_{3} \mathrm{N}_{2}(s) + 6 \mathrm{H}_{2} \mathrm{O}(l) \rightarrow 3 \mathrm{Mg(OH)}_{2}(aq) + 2 \mathrm{NH}_{3}(g) \)

Step 7: (g) Reaction of NaH with water

When sodium hydride (NaH) reacts with water (H2O), the products formed are sodium hydroxide (NaOH) and hydrogen gas (H2). The balanced chemical equation for this reaction is: \( \mathrm{NaH}(s) + \mathrm{H}_{2} \mathrm{O}(l) \rightarrow \mathrm{NaOH}(aq) + \mathrm{H}_{2}(g) \)

Key Concepts

Balanced Chemical Equations

Understanding balanced chemical equations is fundamental in studying chemical reactions. In a balanced equation, the number of atoms of each element is equal on both the reactant and product sides, adhering to the Law of Conservation of Mass. For instance, in the reaction of sodium hydride with water, the equation is balanced as such:
\( \text{NaH}(s) + \text{H}_2\text{O}(l) \rightarrow \text{NaOH}(aq) + \text{H}_2(g) \).
Notice how there is one sodium, hydrogen, and oxygen atom on each side, ensuring mass is conserved. When writing balanced chemical equations, all reactants and products must be identified, states of matter should be included, and coefficients must be adjusted to balance the atoms. This practice is not just a theoretical requirement; it has practical implications in predicting the amounts of substances consumed and produced in chemical reactions.

Reaction of Nonmetals with Water

Nonmetals can react with water, often forming acidic or gaseous products. For instance, when sulfur dioxide reacts with water, it forms sulfurous acid:
\( \text{SO}_2(g) + \text{H}_2\text{O}(l) \rightarrow \text{H}_2\text{SO}_3(aq) \).
Another example is the reaction of dichlorine heptoxide to yield perchloric acid:
\( \text{Cl}_2\text{O}_7(g) + \text{H}_2\text{O}(l) \rightarrow 2\text{HClO}_4(aq) \).
These reactions are important in environmental chemistry, as they can lead to acid rain formation when such nonmetal oxides dissolve in atmospheric moisture. Students must remember that while some nonmetals react vigorously with water, others might be less reactive or do not react under normal conditions.

Reaction of Metals with Water

Metals react with water in various ways, depending on their reactivity. Highly reactive metals like sodium rapidly react even with cold water to form hydroxides and release hydrogen gas. Less reactive metals might require higher temperatures or do not react at all. For example, in the provided exercises:

Reaction of Sodium Peroxide:

Sodium peroxide, a strong oxidizer, reacts with water to produce sodium hydroxide and oxygen:
\( \text{Na}_2\text{O}_2(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq) + \text{O}_2(g) \).
Other reactions involving metals with water include the formation of hydroxides, such as barium hydroxide from barium carbide and water, and magnesium hydroxide from magnesium nitride and water. These reactions are not only academically interesting but also have industrial relevance, such as in the production of various compounds and in the generation of gases.

Hydrolysis Reactions

Hydrolysis reactions are a specific type of chemical reaction where a compound reacts with water, causing a chemical breakdown. These reactions are crucial in both organic and inorganic chemistry. For instance, barium carbide reacts with water to yield barium hydroxide and acetylene gas via hydrolysis:
\( \text{BaC}_2(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{Ba(OH)}_2(aq) + \text{C}_2\text{H}_2(g) \).
Hydrolysis can also be seen when rubidium superoxide reacts with water to form rubidium hydroxide and oxygen gas. These types of reactions are integral to understanding chemical processes like corrosion, digestion, and even the functioning of ecosystems. In an educational context, mastering hydrolysis reactions can empower students to predict and explain the outcomes of interactions between substances and water.