Question

Write balanced equations describing the reaction of lithium metal with each of the following: \(\mathrm{O}_{2}, \mathrm{~S}, \mathrm{Cl}_{2}, \mathrm{P}_{4}, \mathrm{H}_{2}, \mathrm{H}_{2} \mathrm{O}\), and \(\mathrm{HCl}\).

Short answer

The balanced equations for the reaction of lithium with various substances are as follows: 1. \(4 \mathrm{Li} + \mathrm{O}_{2} \rightarrow 2\mathrm{Li}_{2}\mathrm{O}\) 2. \(2\mathrm{Li} + \mathrm{S} \rightarrow \mathrm{Li}_{2}\mathrm{S}\) 3. \(2\mathrm{Li} + \mathrm{Cl}_{2} \rightarrow 2\mathrm{LiCl}\) 4. \(12 \mathrm{Li} + \mathrm{P}_{4} \rightarrow 4\mathrm{Li}_{3}\mathrm{P}\) 5. \(2 \mathrm{Li} + \mathrm{H}_{2} \rightarrow 2\mathrm{LiH}\) 6. \(2\mathrm{Li} + 2\mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{LiOH} + \mathrm{H}_{2}\) 7. \(2\mathrm{Li} + 2\mathrm{HCl} \rightarrow 2\mathrm{LiCl} + \mathrm{H}_{2}\)

Step-by-step solution

Reaction with O₂ (oxygen gas)

Lithium (Li) reacts with O₂ (oxygen gas) to form lithium oxide (Li₂O). In order to balance the equation, we need to have the same number of Li and O atoms on both sides. The balanced equation for this reaction is: \[4 \mathrm{Li} + \mathrm{O}_{2} \rightarrow 2\mathrm{Li}_{2}\mathrm{O}\]

Reaction with S (sulfur)

Lithium (Li) reacts with S (sulfur) to form lithium sulfide (Li₂S). In order to balance the equation, we need to have the same number of Li and S atoms on both sides. The balanced equation for this reaction is: \[2\mathrm{Li} + \mathrm{S} \rightarrow \mathrm{Li}_{2}\mathrm{S}\]

Reaction with Cl₂ (chlorine gas)

Lithium (Li) reacts with Cl₂ (chlorine gas) to form lithium chloride (LiCl). In order to balance the equation, we need to have the same number of Li and Cl atoms on both sides. The balanced equation for this reaction is: \[2\mathrm{Li} + \mathrm{Cl}_{2} \rightarrow 2\mathrm{LiCl}\]

Reaction with P₄ (phosphorus)

Lithium (Li) reacts with P₄ (phosphorus) to form lithium phosphide (Li₃P). In order to balance the equation, we need to have the same number of Li and P atoms on both sides. The balanced equation for this reaction is: \[12 \mathrm{Li} + \mathrm{P}_{4} \rightarrow 4\mathrm{Li}_{3}\mathrm{P}\]

Reaction with H₂ (hydrogen gas)

Lithium (Li) reacts with H₂ (hydrogen gas) to form lithium hydride (LiH). In order to balance the equation, we need to have the same number of Li and H atoms on both sides. The balanced equation for this reaction is: \[2 \mathrm{Li} + \mathrm{H}_{2} \rightarrow 2\mathrm{LiH}\]

Reaction with H₂O (water)

Lithium (Li) reacts with H₂O (water) to form lithium hydroxide (LiOH) and hydrogen gas (H₂). In order to balance the equation, we need to have the same number of Li, O, and H atoms on both sides. The balanced equation for this reaction is: \[2\mathrm{Li} + 2\mathrm{H}_{2}\mathrm{O} \rightarrow 2\mathrm{LiOH} + \mathrm{H}_{2}\]

Reaction with HCl (hydrochloric acid)

Lithium (Li) reacts with HCl (hydrochloric acid) to form lithium chloride (LiCl) and hydrogen gas (H₂). In order to balance the equation, we need to have the same number of Li, Cl, and H atoms on both sides. The balanced equation for this reaction is: \[2\mathrm{Li} + 2\mathrm{HCl} \rightarrow 2\mathrm{LiCl} + \mathrm{H}_{2}\]

Key concepts

Balancing Equations

Balancing chemical equations is a fundamental skill in chemistry that ensures chemical equations accurately represent the law of conservation of mass. Each side of the equation must have the same number of atoms of each element.

To balance an equation, start by writing the unbalanced equation with the correct formulas for all reactants and products. Focus on balancing one element at a time, using coefficients to equalize the number of atoms for each element on both sides.

• In the reaction of lithium (Li) with oxygen (O₂) to form lithium oxide (Li₂O), the balanced equation is: \[4\mathrm{Li} + \mathrm{O}_{2} \rightarrow 2\mathrm{Li}_{2}\mathrm{O}\]. This ensures four lithium atoms and two oxygen atoms on each side.
• Repeat this process for each reaction, ensuring the atom counts match up.

Balancing equations may require trial and error, but with practice, identifying common patterns and using simple strategies, like starting with molecules that appear in multiple compounds, can make the process easier.

Lithium Reactions

Lithium, the lightest metal and one of the alkali metals, reacts readily with various substances. Its reactions are unique because lithium often forms simple ionic compounds where it exists as a positive ion, \(\mathrm{Li}^+\).

When lithium reacts with oxygen, it forms lithium oxide (Li₂O), producing an ionic bond between lithium and oxygen. Lithium also reacts with other non-metals, such as sulfur and chlorine:

• With sulfur, lithium forms lithium sulfide (\(\mathrm{Li}_2\mathrm{S}\)), a compound where lithium donates electrons to sulfur.
• With chlorine, lithium forms lithium chloride (\(\mathrm{LiCl}\)), which is a white solid at room temperature.

These reactions demonstrate lithium's propensity to lose one electron, achieving the stable configuration of helium.

Stoichiometry

Stoichiometry involves calculating the quantities of reactants and products in a chemical reaction. It's based on the balanced chemical equation and the principle that matter is conserved, thus ensuring that the mass of reactants equals the mass of products.

A balanced chemical equation is a tool that allows you to understand the proportional relationships between reactants and products. For instance, in the reaction of lithium with hydrogen gas to form lithium hydride (LiH):

• The balanced equation \( 2 \mathrm{Li} + \mathrm{H}_2 \rightarrow 2 \mathrm{LiH} \) tells you that two atoms of lithium will produce two formula units of lithium hydride for every molecule of hydrogen gas used.
• By using stoichiometric coefficients, one can calculate how much lithium or hydrogen is needed to produce a certain amount of lithium hydride.

Understanding stoichiometry ensures that reactions are carried out efficiently, with minimal waste of resources.

Oxidation-Reduction Reactions

Oxidation-reduction (redox) reactions are chemical reactions where electrons are transferred between atoms. This process involves the oxidation of one element (losing electrons) and the reduction of another (gaining electrons).

In many lithium reactions, lithium is oxidized while the other element is reduced. For example:

• When lithium reacts with oxygen, lithium loses electrons (oxidation) to form \(\mathrm{Li}^+\) ions, and oxygen gains those electrons (reduction) to form oxide ions (\(\mathrm{O}^{2-}\)).
• This electron transfer gives lithium oxide its structure and charge balance.

Oxidation numbers help track electron transfer: lithium starts at 0 and becomes +1 after losing an electron, while oxygen moves from 0 to -2 after gaining electrons.

Understanding redox reactions is vital because these reactions are foundational to processes like metabolism, combustion, and corrosion, and are widely applied in industries like battery manufacturing.