Problem 30 - 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: Determine the Oxide Forming Metal

Lithium tends to form normal oxides when it reacts with oxygen. The balanced chemical equation for lithium reacting with oxygen is given as:\[ 4\text{Li} + \text{O}_2 \rightarrow 2\text{Li}_2\text{O} \]Here, \(\text{Li}_2\text{O}\) is lithium oxide.

Step 2: Determine the Peroxide Forming Metal

Sodium tends to form peroxides with oxygen. The balanced chemical equation for sodium reacting with oxygen is given as:\[ 2\text{Na} + \text{O}_2 \rightarrow \text{Na}_2\text{O}_2 \]In this reaction, \(\text{Na}_2\text{O}_2\) represents sodium peroxide.

Step 3: Determine the Superoxide Forming Metal

Potassium tends to form superoxides when reacting with oxygen. The balanced equation for potassium with oxygen is:\[ \text{K} + \text{O}_2 \rightarrow \text{KO}_2 \]Here, \(\text{KO}_2\) is potassium superoxide.

Key Concepts

Balanced Chemical Equations

Balanced chemical equations are essential in chemistry because they show the exact proportions in which elements react and products form. For a chemical equation to be balanced, the number of atoms for each element on the reactants side must equal those on the products side. This is because, according to the law of conservation of mass, matter cannot be created or destroyed in a chemical reaction.

When balancing chemical equations, you'll often follow these steps:

• Identify the reactants and products.
• Count the number of atoms for each element in both the reactants and products.
• Add coefficients to make the numbers of atoms of each element equal on both sides.
• Check your work to ensure the balance is correct.

In the given exercise, lithium, sodium, and potassium react with oxygen to form different compounds. Each chemical equation is balanced by adjusting the number of each reactant and product molecule so that the atoms on each side are equal.

Oxides

Oxides are compounds formed when elements react with oxygen, and they often exhibit a wide range of properties. Metal oxides are typically formed when metals react with oxygen, and they play a crucial role in many chemical processes.

Lithium forms an oxide when it reacts with oxygen. The balanced equation for this reaction is: \[ 4\text{Li} + \text{O}_2 \rightarrow 2\text{Li}_2\text{O} \]Here, \(\text{Li}_2\text{O}\) is lithium oxide. This type of oxide has basic properties and is involved in various industrial applications. Lithium oxide can react with water to form lithium hydroxide, a useful substance in many chemical reactions.

Peroxides

Peroxides contain an oxygen-oxygen single bond and are characterized by the formula \(\text{M}_2\text{O}_2\), where \(\text{M}\) is a metal. These compounds are less stable compared to normal oxides due to the presence of the peroxo bond \((\text{O}_2^{2-})\).

Sodium forms a peroxide when it reacts with oxygen. The balanced chemical equation is: \[ 2\text{Na} + \text{O}_2 \rightarrow \text{Na}_2\text{O}_2 \]In this equation, \(\text{Na}_2\text{O}_2\) is sodium peroxide. Peroxides are often reactive and can decompose to release oxygen gas, a property utilized in various industrial processes such as bleaching and disinfection. Sodium peroxide, specifically, can be used in the purification of drinking water.

Superoxides

Superoxides are unique compounds characterized by the presence of the superoxide ion \((\text{O}_2^-)\). They form primarily with alkali metals and have the general formula \(\text{MO}_2\). The superoxide ion can stabilize highly reactive oxygen species, making superoxides highly reactive as well.

Potassium forms a superoxide with oxygen, and the balanced equation is: \[ \text{K} + \text{O}_2 \rightarrow \text{KO}_2 \]Here, \(\text{KO}_2\) is potassium superoxide. Superoxides are known for their strong oxidizing properties and can be utilized in emergency oxygen supply systems because they can release oxygen when decomposed. Additionally, they participate in oxidative processes important in batteries and some chemical syntheses.