Consider the reaction $$6 \mathrm{Li}(s)+\mathrm{N}_{2}(g) \longrightarrow 2 \mathrm{Li}_{3} \mathrm{~N}(s)$$ Without doing any detailed calculations, choose one of the following combinations in which nitrogen is the limiting reactant: (a) \(44 \mathrm{~g} \mathrm{Li}\) and \(38 \mathrm{~g} \mathrm{~N}_{2}\) (b) \(1380 \mathrm{~g} \mathrm{Li}\) and \(842 \mathrm{~g} \mathrm{~N}_{2}\) (c) \(1.1 \mathrm{~g} \mathrm{Li}\) and \(0.81 \mathrm{~g} \mathrm{~N}_{2}\)

Stoichiometry is the backbone of chemical calculations, and understanding it is crucial for diving into any chemical reaction. It's all about the relative quantities of reactants and products involved in a reaction. Think of it as a recipe: Stoichiometry tells you how much of each ingredient you need to make a certain amount of product. In our exercise, for every 1 mole of nitrogen gas (2), you need 6 moles of lithium () to produce 2 moles of lithium nitride (3).

When solving a stoichiometry problem, the first step is always to identify the balanced equation, which gives us the mole ratios of reactants to products. It's a proportional relationship and sets the stage for all subsequent calculations. To tackle more complex problems, one must be comfortable with converting between moles, grams, liters, and particles, using Avogadro's number and molar masses. Remember, stoichiometry is not just about numbers; it's a concept that provides insight into the core of chemical reactions—how substances interact in definite ratios.

Now that we've got stoichiometry down, let's focus on the mole-to-mass ratio. It's a simple yet powerful tool that connects the moles of a substance to its mass in grams. Here's where the molecular weight (also known as the molar mass) comes into play. It gives us the weight of one mole of a substance. For example, with lithium having a molecular weight of approximately 7 g/mol, we can easily convert grams to moles and vice versa.

In our exercise, understanding the mole-to-mass ratio helps us compare the given masses of reactants. To analyze which reactant is limiting, we convert the given masses to moles. Contrasting these mole amounts to the required stoichiometric ratio enables us to spot the limiting reactant—the one in short supply that determines the extent of the reaction. Practicing mole-to-mass conversions will make you adept at navigating through the fascinating world of chemical equations, enhancing your problem-solving skills in chemistry.

Analyzing chemical reactions goes hand-in-hand with stoichiometry and mole-to-mass conversions. We can dissect a reaction much like a detective examines a case, looking for clues that lead to a conclusion. By inspecting the balanced chemical equation, we identify which reactant will run out first—the limiting reactant—and which one we'll have left over—the excess reactant.

In our reaction, 6 moles of lithium react with 1 mole of nitrogen. Without detailed calculations, we ascertain the limiting reactant by simply comparing mole ratios derived from given masses with stoichiometric ratios. Focusing on ratios, rather than getting lost in complex calculations, often yields solutions more efficiently. In our choices, we quickly see that choice (c) matches the stoichiometric requirements for nitrogen to be limiting. Mastering chemical reaction analysis will provide you with a lens to view the intriguing exchange of elements and compounds, crucial for anyone passionate about the chemical sciences.