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) \(\mathrm{BaC}_{2}(\mathrm{~s})\), (e) \(\mathrm{RbO}_{2}(\mathrm{~s})\), (f) \(\mathrm{Mg}_{3} \mathrm{~N}_{2}(s)\) (g) \(\mathrm{NaH}(s)\).

Short answer

(a) \( SO_{2}(g) + H_{2}O(l) \rightarrow H_{2}SO_{3}(aq) \) (b) \( Cl_{2}O_{7}(g) + H_{2}O(l) \rightarrow 2 HClO_{4}(l) \) (c) \( Na_{2}O_{2}(s) + 2 H_{2}O(l) \rightarrow 2 NaOH(aq) + O_{2}(g) \) (d) \( BaC_{2}(s) + 2 H_{2}O(l) \rightarrow Ba(OH)_{2}(aq) + C_{2}H_{2}(g) \) (e) \( RbO_{2}(s) + 2 H_{2}O(l) \rightarrow 2 RbOH(aq) + O_{2}(g) \) (f) \( Mg_{3}N_{2}(s) + 6 H_{2}O(l) \rightarrow 3 Mg(OH)_{2}(aq) + 2 NH_{3}(g) \) (g) \( NaH(s) + H_{2}O(l) \rightarrow NaOH(aq) + H_{2}(g) \)

Step-by-step solution

(a) Reaction of SO2(g) with water

Sulfur dioxide (SO2) is an acidic oxide that will react with water in a hydrolysis reaction to form sulfurous acid (H2SO3). The chemical equation for this reaction can be written as: \( SO_{2}(g) + H_{2}O(l) \rightarrow H_{2}SO_{3}(aq) \) The equation is already balanced.

(b) Reaction of Cl2O7(g) with water

Chlorine heptoxide (Cl2O7) is an acidic oxide. It will react with water to form perchloric acid (HClO4). The chemical equation for this reaction is: \( Cl_{2}O_{7}(g) + H_{2}O(l) \rightarrow 2 H_{2}O_{4}(l) \) The equation is now balanced.

(c) Reaction of Na2O2(s) with water

Sodium peroxide (Na2O2) is a peroxide and will decompose in the presence of water to release oxygen gas and form a hydroxide ion. The chemical equation for this reaction is: \( Na_{2}O_{2}(s) + 2 H_{2}O(l) \rightarrow 2 NaOH(aq) + O_{2}(g) \) The equation is now balanced.

(d) Reaction of BaC2(s) with water

Barium carbide (BaC2) reacts with water and undergoes hydrolysis to form Barium hydroxide (Ba(OH)2) and acetylene gas (C2H2). The chemical equation for this reaction is: \( BaC_{2}(s) + 2 H_{2}O(l) \rightarrow Ba(OH)_{2}(aq) + C_{2}H_{2}(g) \) The equation is now balanced.

(e) Reaction of RbO2(s) with water

Rubidium peroxide (RbO2) is a peroxide and will decompose when in contact with water to release oxygen gas and form rubidium hydroxide (RbOH). The chemical equation for this reaction is: \( RbO_{2}(s) + 2 H_{2}O(l) \rightarrow 2 RbOH(aq) + O_{2}(g) \) The equation is now balanced.

(f) Reaction of Mg3N2(s) with water

Magnesium nitride (Mg3N2) reacts with water in a hydrolysis reaction to form magnesium hydroxide (Mg(OH)2) and ammonia gas (NH3). The chemical equation for this reaction is: \( Mg_{3}N_{2}(s) + 6 H_{2}O(l) \rightarrow 3 Mg(OH)_{2}(aq) + 2 NH_{3}(g) \) The equation is now balanced.

(g) Reaction of NaH(s) with water

Sodium hydride (NaH) reacts with water in an acid-base reaction to form sodium hydroxide (NaOH) and hydrogen gas (H2). The chemical equation for this reaction is: \( NaH(s) + H_{2}O(l) \rightarrow NaOH(aq) + H_{2}(g) \) The equation is now balanced.

Key concepts

Acidic Oxides

Acidic oxides are a group of oxides that react with water to form acidic solutions. These are typically non-metal oxides. A common example is sulfur dioxide (\( \text{SO}_{2} \)), which reacts with water to produce sulfurous acid (\( \text{H}_{2}\text{SO}_{3} \)).
The chemical equation for this reaction illustrates a classic acidic behavior:

• \( \text{SO}_{2}(g) + \text{H}_{2}\text{O}(l) \rightarrow \text{H}_{2}\text{SO}_{3}(aq) \)

Another example is chlorine heptoxide (\( \text{Cl}_{2}\text{O}_{7} \)), forming perchloric acid (\( \text{HClO}_{4} \)) when it reacts with water:

• \( \text{Cl}_{2}\text{O}_{7}(g) + \text{H}_{2}\text{O}(l) \rightarrow 2 \text{HClO}_{4}(l) \)

Understanding acidic oxides is important as it helps predict the nature of the substances formed when these oxides dissolve in water. It is an integral concept in predicting reactions and understanding environmental phenomena such as acid rain.

Basic Oxides

Basic oxides are typically metal oxides that react with water to produce a basic solution. These are also known as alkaline oxides. A classic example of a basic oxide is sodium peroxide (\( \text{Na}_{2}\text{O}_{2} \)), which forms sodium hydroxide (\( \text{NaOH} \)) and releases oxygen gas when it reacts with water:

• \( \text{Na}_{2}\text{O}_{2}(s) + 2 \text{H}_{2}\text{O}(l) \rightarrow 2 \text{NaOH}(aq) + \text{O}_{2}(g) \)

Similarly, rubidium peroxide (\( \text{RbO}_{2} \)) reacts with water in a similar manner:

• \( \text{RbO}_{2}(s) + 2 \text{H}_{2}\text{O}(l) \rightarrow 2 \text{RbOH}(aq) + \text{O}_{2}(g) \)

These reactions are essential in understanding the behavior of metal oxides in aqueous environments. By knowing how these compounds interact with water, chemists can predict the resulting pH and reactivity in different contexts.

Hydrolysis Reactions

Hydrolysis reactions occur when a chemical compound reacts with water, leading to the dissociation and formation of new products. This process is pivotal in chemical transformations, especially with compounds like \( \text{BaC}_{2} \) and \( \text{Mg}_{3}\text{N}_{2} \).
For instance, barium carbide \( \text{BaC}_{2} \) undergoes hydrolysis to form barium hydroxide (\( \text{Ba(OH)}_{2} \)) and acetylene gas (\( \text{C}_{2}\text{H}_{2} \)):

• \( \text{BaC}_{2}(s) + 2 \text{H}_{2}\text{O}(l) \rightarrow \text{Ba(OH)}_{2}(aq) + \text{C}_{2}\text{H}_{2}(g) \)

Additionally, magnesium nitride \( \text{Mg}_{3} ext{N}_{2} \) reacts with water to produce magnesium hydroxide (\( \text{Mg(OH)}_{2} \)) and ammonia gas (\( \text{NH}_{3} \)):

• \( \text{Mg}_{3}\text{N}_{2}(s) + 6 \text{H}_{2}\text{O}(l) \rightarrow 3 \text{Mg(OH)}_{2}(aq) + 2 \text{NH}_{3}(g) \)

Hydrolysis stands out as a crucial concept for understanding how specific compounds decompose in the presence of water, broadening our comprehension of chemical stability and transformation.

Chemical Equation Balancing

Balancing chemical equations is a fundamental skill in chemistry that ensures the conservation of mass. The number and type of atoms on the reactant side must equal those on the product side. Consider the following example:
When sodium hydride (\( \text{NaH} \)) reacts with water, it forms sodium hydroxide (\( \text{NaOH} \)) and hydrogen gas (\( \text{H}_{2} \)):

• \( \text{NaH}(s) + \text{H}_{2}\text{O}(l) \rightarrow \text{NaOH}(aq) + \text{H}_{2}(g) \)

This equation shows one sodium atom, one hydrogen atom, and one oxygen atom balancing both sides.

• Sodium: 1 on each side
• Hydrogen: 2 on each side
• Oxygen: 1 on each side

Balancing chemical equations ensures accurate representation of chemical reactivity and is crucial to further studies and applications of chemistry, such as stoichiometry and reaction predictions.