How does the limiting reactant change?

Reagents that are capable of reacting will react; the "limiting" factor simply refers to which reagent has more material available; stoichiometrically speaking, the reagent with the least material "limits" the reaction by being consumed first.

This indicates that a complete, 100% reaction with no upper limit on the production of two moles of water requires two moles of hydrogen for every mole of oxygen.

There will be some oxygen left over after the hydrogen has all been consumed, but only half of the oxygen can react and only ONE mole of water can be created if there is ONLY ONE mole of hydrogen present.

Hydrogen is therefore the "limiting reagent" in this instance.

It changes based on the initial amounts of reactants and their stoichiometric coefficients in the balanced chemical equation.

The limiting reactant in a chemical reaction can change depending on the stoichiometry of the reaction and the quantities of reactants initially present. The limiting reactant is the reactant that is completely consumed first, thereby limiting the amount of product that can be formed.

There are a few scenarios in which the limiting reactant can change:

1. Change in Reactant Quantities: If the quantities of reactants are altered, the limiting reactant can change. For example, adding more of one reactant or removing some of another can shift which reactant is in excess and which is limiting.

2. Different Stoichiometries: In reactions involving multiple reactants, the stoichiometry of the reaction determines how much product can be formed from each reactant. If the stoichiometry of the reaction is altered, for instance by changing the coefficients in a balanced chemical equation, it can affect which reactant is limiting.

3. External Factors: Changes in temperature, pressure, or the presence of a catalyst can alter the reaction rate and, consequently, the consumption rates of reactants. This can lead to a change in the limiting reactant.

4. Reactant Purity: Impurities in reactants can affect the reaction efficiency and alter which reactant is consumed first. A reactant with higher purity may become the limiting reactant compared to one with lower purity.

In summary, the limiting reactant in a chemical reaction can change due to alterations in reactant quantities, changes in stoichiometry, external factors influencing reaction rates, and variations in reactant purity. Understanding the concept of limiting reactants is crucial for predicting the maximum amount of product that can be formed in a reaction.