Limiting reactant pdf

A balanced chemical equation shows the molar amounts of reactants that will react together to produce molar amounts of products. In the real world, reactants are rarely brought together with the exact amount needed.

One reactant will be completely used up before the others. The other reactants are partially consumed where the remaining amount is considered "in excess". This example problem demonstrates a method to determine the limiting reactant of a chemical reaction. To determine the limiting reactant, calculate the amount of product formed by each reactant.

The reactant the produces the least amount of product is the limiting reactant. The sodium hydroxide formed less product than the phosphoric acid. This means the sodium hydroxide was the limiting reactant and To determine the amount of excess reactant remaining, the amount used is needed. Share Flipboard Email. By Todd Helmenstine. Todd Helmenstine is a science writer and illustrator who has taught physics and math at the college level. He holds bachelor's degrees in both physics and mathematics. Updated September 05, If How many grams of Na 3 PO 4 are formed?

What is the limiting reactant? How many grams of the excess reactant remains when the reaction is complete? Useful information:. To determine the number of grams of Na 3 PO 4 formed:. Amount of Na 3 PO 4 formed from This number can be used to determine the remaining amount of excess reactant. When NaOH was the limiting reactant.In all the examples discussed thus far, the reactants were assumed to be present in stoichiometric quantities. Consequently, none of the reactants was left over at the end of the reaction.

This is often desirable, as in the case of a space shuttle, where excess oxygen or hydrogen was not only extra freight to be hauled into orbit but also an explosion hazard.

More often, however, reactants are present in mole ratios that are not the same as the ratio of the coefficients in the balanced chemical equation. As a result, one or more of them will not be used up completely but will be left over when the reaction is completed. In this situation, the amount of product that can be obtained is limited by the amount of only one of the reactants. The reactant that restricts the amount of product obtained is called the limiting reactant. The reactant that remains after a reaction has gone to completion is in excess.

Consider a nonchemical example. Assume you have invited some friends for dinner and want to bake brownies for dessert. You find two boxes of brownie mix in your pantry and see that each package requires two eggs. The balanced equation for brownie preparation is thus. If you have a dozen eggs, which ingredient will determine the number of batches of brownies that you can prepare? Because each box of brownie mix requires two eggs and you have two boxes, you need four eggs.

Twelve eggs is eight more eggs than you need. Although the ratio of eggs to boxes in isthe ratio in your possession is Hence the eggs are the ingredient reactant present in excess, and the brownie mix is the limiting reactant.

Even if you had a refrigerator full of eggs, you could make only two batches of brownies. Consider this concept now with regard to a chemical process, the reaction of hydrogen with chlorine to yield hydrogen chloride:. The balanced equation shows the hydrogen and chlorine react in a stoichiometric ratio. If these reactants are provided in any other amounts, one of the reactants will nearly always be entirely consumed, thus limiting the amount of product that may be generated.

This substance is the limiting reactant, and the other substance is the excess reactant. Identifying the limiting and excess reactants for a given situation requires computing the molar amounts of each reactant provided and comparing them to the stoichiometric amounts represented in the balanced chemical equation. For example, imagine combining 3 moles of H 2 and 2 moles of Cl 2. This represents a or 1.

Hydrogen, therefore, is present in excess, and chlorine is the limiting reactant. Reaction of all the provided chlorine 2 mol will consume 2 mol of the 3 mol of hydrogen provided, leaving 1 mol of hydrogen nonreacted.

An alternative approach to identifying the limiting reactant involves comparing the amount of product expected for the complete reaction of each reactant. The reactant yielding the lesser amount of product is the limiting reactant.

For the example in the previous paragraph, complete reaction of the hydrogen would yield. The chlorine will be completely consumed once 4 moles of HCl have been produced. Since enough hydrogen was provided to yield 6 moles of HCl, there will be non-reacted hydrogen remaining once this reaction is complete.

A similar situation exists for many chemical reactions: you usually run out of one reactant before all of the other reactant has reacted. The reactant you run out of is called the limiting reactant; t he other reactant or reactants are considered to be in excess. A crucial skill in evaluating the conditions of a chemical process is to determine which reactant is the limiting reactant and which is in excess.

There are two ways to determine the limiting reagent. One method is to find and compare the mole ratio of the reactants used in the reaction Approach 1. Another way is to calculate the grams of products produced from the given quantities of reactants; the reactant that produces the smallest amount of product is the limiting reagent Approach 2.In a chemical reaction, the limiting reagent, or limiting reactant, is the substance that has been completely consumed when the chemical reaction is complete.

The amount of product produced by the reaction is limited by this reactant because the reaction cannot proceed further without it; often, other reagents are present in excess of the quantities required to to react with the limiting reagent.

From stoichiometry, the exact amount of reactant needed to react with another element can be calculated. However, if the reagents are not mixed or present in these correct stoichiometric proportions, the limiting reagent will be entirely consumed and the reaction will not go to stoichiometric completion.

One way to determine the limiting reagent is to compare the mole ratio of the amount of reactants used. This method is most useful when there are only two reactants. One reactant A is chosen, and the balanced chemical equation is used to determine the amount of the other reactant B necessary to react with A. If the amount of B actually present exceeds the amount required, then B is in excess, and A is the limiting reagent.

If the amount of B present is less than is required, then B is the limiting reagent. To begin, the chemical equation must first be balanced. The law of conservation states that the quantity of each element does not change over the course of a chemical reaction.

Therefore, the chemical equation is balanced when the amount of each element is the same on both the left and right sides of the equation. Next, convert all given information typically masses into moles, and compare the mole ratios of the given information to those in the chemical equation.

For example: What would be the limiting reagent if 75 grams of C 2 H 3 Br 3 reacted with It is then possible to calculate how much C 2 H 3 Br 3 would be required if all the O 2 is used up:. This demonstrates that 0.

Since there is only 0. Another method of determining the limiting reagent involves the comparison of product amounts that can be formed from each reactant.

This method can be extended to any number of reactants more easily than the previous method. Again, begin by balancing the chemical equation and by converting all the given information into moles. Then use stoichiometry to calculate the mass of the product that could be produced for each individual reactant.

The reactant that produces the least amount of product is the limiting reagent. For example: What would be the limiting reagent if The comparison can be done with either product; for this example, NaOH will be the product compared. To determine how much NaOH is produced by each reagent, use the stoichiometric ratio given in the chemical equation as a conversion factor:.

Then convert the grams of each reactant into moles of NaOH to see how much NaOH each could produce if the other reactant was in excess.

8.5: Limiting Reactant and Theoretical Yield

Boundless vets and curates high-quality, openly licensed content from around the Internet. This particular resource used the following sources:. Skip to main content.When there is not enough of one reactant in a chemical reaction, the reaction stops abruptly. To figure out the amount of product produced, it must be determined reactant will limit the chemical reaction the limiting reagent and which reactant is in excess the excess reagent.

One way of finding the limiting reagent is by calculating the amount of product that can be formed by each reactant; the one that produces less product is the limiting reagent. The following scenario illustrates the significance of limiting reagents. In order to assemble a car, 4 tires and 2 headlights are needed among other things. In this example, imagine that the tires and headlights are reactants while the car is the product formed from the reaction of 4 tires and 2 headlights. If you have 20 tires and 14 headlights, how many cars can be made?

With 20 tires, 5 cars can be produced because there are 4 tires to a car. With 14 headlights, 7 cars can be built each car needs 2 headlights. Although more cars can be made from the headlights available, only 5 full cars are possible because of the limited number of tires available.

In this case, the headlights are in excess. Because the number of cars formed by 20 tires is less than number of cars produced by 14 headlights, the tires are the limiting reagent they limit the full completion of the reaction, in which all of the reactants are used up.

This scenario is illustrated below:. The initial condition is that there must be 4 tires to 2 headlights. The reactants must thus occur in that ratio; otherwise, one will limit the reaction. There are 20 tires and 14 headlights, so there are two ways of looking at this problem. For 20 tires, 10 headlights are required, whereas for 14 headlights, 28 tires are required.

Because there are not enough tires 20 tires is less than the 28 requiredtires are the limiting "reactant. The limiting reagent is the reactant that is completely used up in a reaction, and thus determines when the reaction stops.

Limiting Reagents

From the reaction stoichiometrythe exact amount of reactant needed to react with another element can be calculated. If the reactants are not mixed in the correct stoichiometric proportions as indicated by the balanced chemical equationthen one of the reactants will be entirely consumed while another will be left over.

The limiting reagent is the one that is totally consumed; it limits the reaction from continuing because there is none left to react with the in-excess reactant. There are two ways to determine the limiting reagent. One method is to find and compare the mole ratio of the reactants used in the reaction approach 1. Another way is to calculate the grams of products produced from the given quantities of reactants; the reactant that produces the smallest amount of product is the limiting reagent approach 2. Find the limiting reagent by calculating and comparing the amount of product each reactant will produce. What mass of carbon dioxide forms in the reaction of 25 grams of glucose with 40 grams of oxygen?

Step 1: Determine the balanced chemical equation for the chemical reaction. Step 2: Convert all given information into moles most likely, through the use of molar mass as a conversion factor. Step 3: Calculate the mole ratio from the given information.By Peter J. Mikulecky, Chris Hren. In real-life chemical reactionsnot all of the reactants present convert into product. More typically, one reagent is completely used up, and others are left in excess, perhaps to react another day.

The reactant that is used up is the limiting reagent. Either you have an excess of the first reagent, or you have an excess of the second reagent. The one you have in excess is the excess reagent. Say you are conducting an experiment where ammonia reacts with oxygen to produce nitrogen monoxide and liquid water:. In order to find the limiting reagents, excess reagents, and products in this reaction, you need to do the following:.

Determine the limiting reagent if g of each reagent are present at the beginning of the reaction. Identify the excess reagent, as well as how many grams of the excess reagent will remain when the reaction reaches completion. Calculate how many grams of each product will be produced if the reaction goes to completion. Before doing anything else, you must have a balanced reaction equation.

The balanced form of the given equation is. Two candidates, NH 3 and O 2vie for the status of limiting reagent. You start with g of each, which corresponds to some number of moles of each. Furthermore, you can tell from the coefficients in the balanced equation this reaction requires 4 mol of ammonia for every 5 mol of oxygen gas.

Determine the limiting reagent if g of ammonia and g of oxygen are present at the beginning of the reaction. To find the limiting reactant, you simply need to perform a mass-to-mass gram-to-gram calculation from one reactant to the other. This allows you to see which reactant runs out first. You can start with either reactant and convert to mass of the other. But you have only g of oxygen.

To calculate how many grams of ammonia will be left at the end of the reaction, assume that all g of oxygen react:. This calculation shows that So, the excess reagent is ammonia, and Calculate how many grams of nitrogen monoxide and water will be produced if the reaction goes to completion.

This problem asks how much of a product is produced. For this calculation, you must begin with the limiting reactant. To determine the grams of nitrogen monoxide that are generated by the complete reaction of oxygen, start with the assumption that all g of the oxygen react:.Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.

We welcome your feedback, comments and questions about this site or page. Please submit your feedback or enquiries via our Feedback page. The following Stoichiometry Road Map gives a summary of how to use stoichiometry to calculate moles, masses, volumes and particles in a chemical reaction with limiting and excess reactants.

Scroll down the page for more examples and solutions. Stoichiometry - Limiting and Excess Reactant Introduction to Limiting Reactant and Excess Reactant The limiting reactant or limiting reagent is the first reactant to get used up in a chemical reaction. Once the limiting reactant gets used up, the reaction has to stop and cannot continue and there is extra of the other reactants left over.

Those are called the excess reactants. We will learn about limiting reactant and limiting reagent by comparing chemical reactions to cooking recipes and we will look at an actual stoichiometry problem. Example: What is the greatest amount of NH 3 in moles that can be made with 3. What is the limiting reactant? Which reactant is in excess and how many moles of it are left over? You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics.

Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.In this lesson students learn about limiting reactants, excess reactants, theoretical yield, actual yield, and percent yield. For this lesson there is an activity in the engage section for which students need a ziploc bag filled with nuts and bolts.

I use 18 nuts and 7 bolts. To begin the lesson I have students perform an activity with their groups where they have a chance to figure out what a limiting reactant is using everyday materials. This section is the main part of the lesson where I do notes with my students. The lesson is set up where I first explain the material and then students perform examples. I give students about 40 minutes of class time to start the questions so that they can get help from their partners and so that I can walk around and help them out.

If students do not complete the questions in class I expect them to complete the questions for homework. There was a typo on number 4 in the homework so that they theoretical is 0.

Here is a copy of the fixed practice questions. This is one student's filled in homework. I check the homework for completion the following day by giving students a stamp and then go over the answers with the answer key.

I make sure to take time to go over HOW to answer the questions, especially 3 and 4 which are tricky and 4 which had the mistake. Empty Layer.

Home Professional Learning. Professional Learning. Learn more about. Sign Up Log In. High School Chemistry Rachel Meisner. Students will be able to distinguish limiting versus excess reactants in a chemical reaction as well as calculate percent yield as demonstrated by doing an activity, taking notes, and performing practice questions.

Big Idea In chemical reactions a limiting recant causes a reaction to stop, while an excess reactant is leftover. Additionally one can calculate percent yield using the experimental value from performing a lab and the theoretical value from calculations. Lesson Author. Grade Level. Chemical Reactions and Balancing. 