Question

Complete and balance the equations for the following reactions. a. \(\operatorname{Li}(s)+\mathrm{N}_{2}(g) \rightarrow\) b. \(\operatorname{Rb}(s)+\mathrm{S}(s) \rightarrow\)

Short answer

The short answers for the balanced equations are: a. \(6\operatorname{Li}(s)+\mathrm{N}_{2}(g) \rightarrow 2\operatorname{Li}_{3}\operatorname{N}(s)\) b. \(2\operatorname{Rb}(s)+\mathrm{S}(s) \rightarrow \operatorname{Rb}_{2}\operatorname{S}(s)\)

Step-by-step solution

(a) Identify the product and its stoichiometry

For the reaction between lithium (Li) and nitrogen (N), the product will be a lithium nitride compound. Since lithium has a +1 charge and nitrogen has a -3 charge, the compound formed will be Li3N, with a balanced ratio of charges.

(a) Write the unbalanced equation

Now, we can write the unbalanced equation for the reaction: \( \operatorname{Li}(s)+\mathrm{N}_{2}(g) \rightarrow \operatorname{Li}_{3}\operatorname{N}(s) \)

(a) Balance the equation

To balance the equation, we need to make sure there are equal numbers of each element on both sides of the reaction. We can use the method of coefficients to achieve this: \(6 \operatorname{Li}(s)+\mathrm{N}_{2}(g) \rightarrow 2\operatorname{Li}_{3}\operatorname{N}(s) \) Now, both sides of the equation have 6 lithium (Li) atoms and 2 nitrogen (N) atoms. The final balanced equation for reaction (a) is: \(6\operatorname{Li}(s)+\mathrm{N}_{2}(g) \rightarrow 2\operatorname{Li}_{3}\operatorname{N}(s) \)

(b) Identify the product and its stoichiometry

For the reaction between rubidium (Rb) and sulfur (S), the product will be a rubidium sulfide compound. Since rubidium has a +1 charge and sulfur has a -2 charge, the compound formed will be Rb2S, with a balanced ratio of charges.

(b) Write the unbalanced equation

Now, we can write the unbalanced equation for the reaction: \( \operatorname{Rb}(s)+\mathrm{S}(s) \rightarrow \operatorname{Rb}_{2}\operatorname{S}(s) \)

(b) Balance the equation

To balance the equation, we need to make sure there are equal numbers of each element on both sides of the reaction. We can use the method of coefficients to achieve this: \(2 \operatorname{Rb}(s)+\mathrm{S}(s) \rightarrow \operatorname{Rb}_{2}\operatorname{S}(s) \) Now, both sides of the equation have 2 rubidium (Rb) atoms and 1 sulfur (S) atom. The final balanced equation for reaction (b) is: \(2\operatorname{Rb}(s)+\mathrm{S}(s) \rightarrow \operatorname{Rb}_{2}\operatorname{S}(s) \)

Key concepts

Stoichiometry

Stoichiometry is a crucial concept in chemistry that studies the quantitative relationships between the reactants and products in chemical reactions. It's like the recipe for a chemical reaction, outlining how much of each ingredient you need and what you can expect to get out of it. The core idea of stoichiometry is to ensure that we have balanced chemical equations, meaning the same number of each type of atom on both sides of the reaction.

To achieve this balance, we often use a method called the 'stoichiometric coefficient', which adjusts the number of molecules or atoms involved in the reaction. For example, if you have an unbalanced equation, applying correct stoichiometric coefficients allows you to calculate the exact amounts that satisfy the law of conservation of mass - which states that matter cannot be created or destroyed in a chemical reaction.

Understanding stoichiometry helps in predicting the outcomes of chemical reactions, making it possible to determine how much product will be created from a given amount of reactants, or vice versa. This is fundamental in chemistry lab settings, industrial applications, and even cooking! Everywhere you want to ensure that reactions and transformations yield expected results, stoichiometry is at work.

Lithium Nitride

Lithium nitride is an interesting compound formed from lithium and nitrogen, with the chemical formula \(\text{Li}_3\text{N}\). This compound results from the combination of lithium atoms, having a +1 charge each, and nitrogen atoms, carrying a -3 charge. Thus, each nitrogen atom pairs with three lithium atoms to create a neutral compound.

When balancing a chemical equation involving lithium nitride, like the one given in the exercise, you start by identifying the charges and then progress to writing an unbalanced equation, such as \( \text{Li}(s) + \text{N}_2(g) \rightarrow \text{Li}_3\text{N}(s) \). The equation is then balanced through stoichiometric coefficients. In this case, you would need 6 lithium atoms for every 2 nitrogen atoms, resulting in the balanced equation \(6\text{Li}(s) + \text{N}_2(g) \rightarrow 2\text{Li}_3\text{N}(s)\).

Lithium nitride is unique because it is one of the only alkali metal nitrides that is stable at room temperature. It's a strong reducing agent and finds uses in various applications, including as a storage material for hydrogen.

Rubidium Sulfide

Rubidium sulfide, represented by the chemical formula \(\text{Rb}_2\text{S}\), forms when rubidium and sulfur react. Rubidium atoms carry a +1 charge, while sulfur atoms have a -2 charge. Therefore, two rubidium atoms are necessary to balance the charge of a single sulfur atom, leading to a stable ionic compound.

In balancing a reaction that produces rubidium sulfide, you might start with an unbalanced equation: \( \text{Rb}(s) + \text{S}(s) \rightarrow \text{Rb}_2\text{S}(s) \). Using stoichiometry, we apply coefficients to ensure the equation respects the law of conservation of mass. Here, 2 rubidium atoms interact with 1 sulfur atom, leading to the balanced equation \(2\text{Rb}(s) + \text{S}(s) \rightarrow \text{Rb}_2\text{S}(s) \).

Rubidium sulfide is also significant in various chemical processes and research contexts. As an alkali metal sulfide, it exhibits interesting properties that can be leveraged in various scientific and industrial applications.

Coefficients in Chemical Equations

Coefficients are integral components of chemical equations, used to indicate the number of molecules or atoms of each substance involved in a reaction. They serve to balance equations, ensuring that the same amount of each element is present on both sides of the equation.

In practice, coefficients adjust the proportions of reactants and products without altering the compound's identity. For example, in the reaction forming lithium nitride, placing a coefficient of 6 before the \(\text{Li}(s)\) and 2 before the \(\text{Li}_3\text{N}(s)\) balances the equation \(6\text{Li}(s) + \text{N}_2(g) \rightarrow 2\text{Li}_3\text{N}(s)\).

Using coefficients is essential for accurate stoichiometric calculations, which predict product yields, reactant needs, and more. They help to maintain the law of conservation of mass, affirming the fundamental chemistry principle that atoms are neither lost nor gained during chemical reactions.