Problem 22 - Chemistry and Chemical Reactivity

Question

Write balanced equations for the reaction of lithium, sodium, and potassium with \(\mathrm{O}_{2}\). Specify which metal forms an oxide, which forms a peroxide, and which forms a superoxide.

Step-by-Step Solution

Answer

Lithium forms an oxide, sodium forms a peroxide, and potassium forms a superoxide.

Step 1: Understand the Reaction

In this task, we are balancing the chemical equations for the reactions of lithium (Li), sodium (Na), and potassium (K) with oxygen ( O_2). We'll determine which metal forms an oxide, peroxide, or superoxide based on their reactivity with oxygen.

Step 2: Writing Lithium Reaction

Lithium reacts with oxygen to form lithium oxide. The balanced chemical equation for this reaction is:\[ 4 ext{Li} + ext{O}_2 ightarrow 2 ext{Li}_2 ext{O} \]

Step 3: Writing Sodium Reaction

Sodium reacts with oxygen to form sodium peroxide. The balanced chemical equation is:\[ 2 ext{Na} + ext{O}_2 ightarrow ext{Na}_2 ext{O}_2 \]

Step 4: Writing Potassium Reaction

Potassium reacts with oxygen to form potassium superoxide. The balanced chemical equation is:\[ ext{K} + ext{O}_2 ightarrow ext{KO}_2 \]

Step 5: Identify the Type of Compound Formed

- Lithium forms an oxide (Li₂O). - Sodium forms a peroxide (Na₂O₂). - Potassium forms a superoxide (KO₂).

Key Concepts

Balancing Equations

Balancing chemical equations is an essential skill in chemistry that ensures the conservation of mass, meaning the number of atoms for each element in the reactants equals the number in the products. To balance an equation, adjust the coefficients—numbers placed before compounds—so that all elements have the same number on both sides of the reaction. For example, in the equation for lithium and oxygen:

• Lithium reaction: \( 4 \mathrm{Li} + \mathrm{O}_2 \rightarrow 2 \mathrm{Li}_2 \mathrm{O} \)

Here, you start by counting the number of Li and O atoms on both sides. For lithium (Li), there are 4 atoms on the left and 4 on the right (as \(2 \times 2=4\)) in \(\mathrm{Li}_2\mathrm{O}\). Oxygen is balanced with 2 atoms on both sides. Using coefficients effectively maintains this balance without altering the chemical nature of the substances involved.

Metal Oxides

Metal oxides result from metals reacting with oxygen, forming ionic compounds where metal cations combine with oxygen anions. These compounds are quite stable.

• Lithium forms \(\mathrm{Li}_2 \mathrm{O}\), a typical metal oxide.

Lithium oxide, specifically, is formed when lithium burns in oxygen, producing a white crystalline solid. Metal oxides are significant in numerous applications, including metallurgy and as precursors in material synthesis. Understanding the properties of metal oxides can provide insights into the reactivity and characteristics of the metals themselves.

Reactivity with Oxygen

The reaction of metals with oxygen varies based on several factors, including the metal's position in the periodic table. Reactivity increases as you move down the alkali metal group, resulting in different oxygen compounds.

• Lithium forms oxides due to its lower reactivity.
• Sodium forms peroxides as it is slightly more reactive.
• Potassium, highly reactive, forms superoxides.

The nature of the oxide, peroxide, or superoxide formed depends on the metal's ability to electron-transfer with oxygen. Understanding this reactivity trend is crucial in predicting the outcomes of metal reactions with oxygen and in practical applications like battery technology.

Alkali Metals Reactions

Alkali metals, located in Group 1 of the periodic table, exhibit unique properties including increasing reactivity as you go down the group. Their reactions with oxygen demonstrate the diversity of compounds formed.

• Lithium reacts to form an oxide (\(\mathrm{Li}_2 \mathrm{O}\)).
• Sodium reacts to form a peroxide (\(\mathrm{Na}_2 \mathrm{O}_2\)).
• Potassium reacts to form a superoxide (\(\mathrm{KO}_2\)).

These reactions are highly exothermic and illustrate the robust electron donation tendencies of alkali metals. Understanding these reactions helps in grasping why these metals behave so differently compared to others, influencing their use in industry and technology.