Consider the reaction: 2 NO(g) + 5 H2(g)-2 NH3(g) + 2 H2O(g) A reaction mixture initially contains 5 moles of NO and 10 moles of H2. Without doing any calculations, determine which set of amounts best represents the mixture after the reactants have reacted as completely as possible. Explain your reasoning. a. 1 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O b. 0 mol NO, 1 mol H2, 5 mol NH3, 5 mol H2O c. 3 mol NO, 5 mol H2, 2 mol NH3, 2 mol H2O d. 0 mol NO, 0 mol H2, 4 mol NH3, 4 mol H2O

The concept of the limiting reactant is one of the foundational ideas in chemical reaction stoichiometry. It refers to the substance that is entirely consumed first during a chemical reaction, dictating the quantity of products that can be formed. It is analogous to the idea of a bottle neck in a production line; no matter how much of the other reactants are available, the reaction cannot continue once the limiting reactant is exhausted.

Understanding how to identify the limiting reactant is crucial. This involves comparing the mole ratio between reactants in the balanced chemical equation to the actual mole ratio present in the reaction. If a reactant is present in a lower stoichiometric ratio than required, it becomes the limiting reactant. In our exercise, by analyzing the mole ratio as given in the balanced equation, we see that NO is the limiting reactant since all of it will be consumed before H2, even though there is more H2 present at the start.

Balancing chemical equations is an essential skill in chemistry, as it ensures the law of conservation of mass is satisfied; the number of atoms for each element must be the same on the reactant and product sides of the equation. When you balance a chemical equation, each side should have the same number of atoms of each element.

In the problem provided, the equation is already balanced with coefficients indicating the mole-to-mole relationships between reactants and products: 2 moles of NO react with 5 moles of H2 to produce 2 moles of NH3 and 2 moles of H2O. These coefficients become valuable tools when determining the limiting reactant, calculating product yields, and understanding the complete stoichiometry of the reaction.

The mole-to-mole ratio in a balanced chemical equation expresses how moles of one substance convert to moles of another. These ratios are directly obtained from the coefficients in the balanced chemical equation. They are vital in predicting how much reactant is needed or how much product will be formed in a reaction.

The example reaction shows a clear mole-to-mole ratio: for every 2 moles of NO, 5 moles of H2 are needed to produce 2 moles of NH3 and 2 moles of H2O. This tells us that if we start with 5 moles of NO, we would theoretically need 12.5 moles of H2 to fully react with the NO. However, only 10 moles of H2 are available, making NO the limiting reactant and subsequently determining the maximum amount of product (NH3 and H2O) that can be formed.