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Chemistry Formulas

Limiting Reactant Formula

A chemical reaction will continue to perform as long as there are the reactants to keep it going. When we use any one of the reactants the chemical reaction stops there. Moreover, the reactant that we use there, we also call the first one as the limiting reactant formula, because it limits the number of the product that will form. Detecting the limiting reactant in a chemical reaction can be done through various types of methods. It is not sufficient to just look at the amounts of each reactant and pick the amount that is less. However, the stoichiometry plays a main and an important role in determining that which reactant truly limits here.

The Steps to Determine the Limiting Reagent or the Limiting Reactant is as Follows:

First of all balance the chemical equation if it is not in a balanced form.

Then, find out the amount of the moles of every reactant in the reaction process.

Calculate the number of products that we can obtain through the complete reaction.

Determine which reactant would produce the minimum amount of the product, and that is the limiting reactant.

Method 1st

Comparison of Reactant Amounts:

This method is best useful when there are only 2 reactants present in the reaction. One reactant A is chosen here, and the balanced chemical equation is useful for determining the amount of the other reactant B that is necessary to react with the A. However, if the amount of B is actually present increases the amount needed, then B is in excess and A is the limiting reactant. If the amount of B present is not as much required, then B is the limiting reactant here.

Method 2nd

Comparison of the Product Amounts Which Can Be Formed from a Single Reactant:

In this technique, the chemical equation is useful for calculating the amount of 1 product that each reactant can produce in the amount present over there. The limiting reactant here is the one that can produce the minimum amount of the product considered. This method is extendable up to any number of reactants quite easier than the 1st method.

Limiting Factor

A limiting factor is basically a variation of a system that, if subject to a minor change, then, as a result, it causes a noticeable change in output or other measures of a type of structure. A factor that is not limiting over a certain domain of the initial conditions may yet be limiting over another domain of the initial conditions, including that of the factor.

Solved Example for You

Question: Identify and recognize the limiting reactant if 5.43 moles of Na are reacting with 4.25 moles of O2 in the following equation:

4Na + O2 → 2Na2O

Solution: One of the simplest and easiest ways for identifying a limiting reactant is to compare how much of the product each reactant will be producing. We will be using the stoichiometry for creating a ratio between the reactants and the products that are present in the chemical equation as follows:

5.43 moles Na x 2 moles Na2O/4 moles Na = 2.72 moles Na2O

(5.43 moles of Na will produce 2.72 moles Na2O)

4.25 moles O2 x 2 moles Na2O/1 mole O2 = 8.50 moles Na2O

(4.25 moles of O2 will produce 8.50 moles Na2O)

In the above reaction, the Na will produce a lesser amount of the Na2O than the O2 will be producing. Therefore, Na is the limiting reactant or reagent here. Notice that the initial amount of the Na is actually greater than the starting amount of the O2 but the stoichiometry shows that the Na will run out before.

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