Explain what a limiting agent is and how to identify it

A limiting agent, also known as a limiting reagent, is a chemical reactant that determines the extent of a chemical reaction. It is the reactant that is completely consumed or used up first, thereby limiting the amount of product that can be formed.

To identify the limiting agent in a chemical reaction, you need to compare the stoichiometry of the reactants and the molar ratios of the reactants to products. Here are the steps to follow:

1. Write a balanced chemical equation: Start by writing a balanced equation for the chemical reaction, ensuring that the number of atoms on both sides of the equation is equal.

2. Convert the given quantities: Convert the given quantities of reactants to moles, using their respective atomic or molecular masses. This can be done using the formula:

Moles = Mass (in grams) / Molar mass

3. Determine the stoichiometry: Look at the coefficients in the balanced equation to determine the stoichiometry. These coefficients represent the molar ratios between reactants and products. For example, if the balanced equation shows 2 moles of reactant A reacting with 3 moles of reactant B, the stoichiometry is 2:3.

4. Calculate the theoretical yield: Calculate the theoretical amount of product that can be formed from each reactant, using the stoichiometry ratios and mole amounts of the reactants. This can be done by multiplying the mole amount of a reactant by its respective stoichiometry ratio.

5. Compare the theoretical yields: Compare the theoretical yields of the products obtained from each reactant. The reactant that produces the least amount of product is the limiting agent.

6. Check for excess reagents: After identifying the limiting agent, you can determine if there are any excess reagents left over. This can be done by subtracting the amount of the limiting agent consumed from the initial amount of the reactant given.

By following these steps, you can identify the limiting agent in a chemical reaction and understand which reactant will be completely used up first, limiting the overall amount of product that can be formed.