For the following reaction, determine the limiting reactant for each of the initial amounts of reactants. 2 Na(s) + Br2(g)-2 NaBr(s) a. 2 mol Na, 2 mol Br2 b. 1.8 mol Na, 1.4 mol Br2 c. 2.5 mol Na, 1 mol Br2 d. 12.6 mol Na, 6.9 mol Br2

Stoichiometry is like the recipe for a chemical reaction. It helps us understand the proportions of reactants required and products formed in a chemical process. It's founded on the conservation of mass, which states that matter is neither created nor destroyed in a chemical reaction. Therefore, if we know the amount of one substance in a reaction, stoichiometry allows us to calculate the amount of all other substances involved.

Imagine you are baking cookies, and the recipe calls for 2 cups of flour for every 1 cup of sugar. This is similar to a mole-to-mole ratio in stoichiometry, which tells you how much of one reactant is needed to react with another. Applying stoichiometry to chemical reactions enables us to predict the quantities of products we will end up with or how much of each reactant we need to start with to avoid waste.

A balanced chemical reaction is the backbone of stoichiometry and ensures that the law of conservation of mass is respected. To balance a reaction, we need to make sure that the number of atoms of each element is the same on both sides of the reaction equation. This is much like making sure you have the same number of each type of Lego block before and after following the instructions to build a model.

Using coefficients, numbers that appear in front of the chemical formulas, enables us to balance these reactions. Our textbook example, 2 Na(s) + Br2(g) → 2 NaBr(s), shows that two sodium atoms will react with one molecule of bromine to form two units of sodium bromide. The coefficients '2' in front of Na and NaBr ensure that all atoms involved are accounted for on both sides of the equation.

A mole-to-mole ratio is derived from the balanced chemical equation and it tells us how many moles of one substance will react with or produce moles of another substance. Just like ratios in cooking tell us how many eggs we need per cup of flour, mole-to-mole ratios inform us how many moles of one reactant are needed to react with another.

In our exercise, the mole-to-mole ratio between Na and Br₂ is 2:1, meaning two moles of sodium will react with one mole of bromine to produce sodium bromide. This ratio is crucial for determining the limiting reactant in a reaction, which is the reactant that will be completely used up first and thus limits the amount of product formed. Understanding mole-to-mole ratios prevents the unnecessary waste of chemicals and allows chemists to use resources efficiently.