Limiting reactants in a recipe answers

Evaluation 34

Chemistry 1 (SCIH 031 062)

Be sure to include ALL pages of this project (including the directions and the assignment) when you send the project to your teacher for grading. Don’t forget to put your name and I.D. number at the top of this page!

This project will count for 10% and is worth 100 points of your overall grade for this course. Be sure to read all the instructions and assemble all the necessary materials before you begin. You will need to print this document and complete it on paper. Feel free to attach extra pages if you need them.

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Project 4- Balancing Equations

Purpose: Writing a balanced chemical equation is at the core of many important chemical concepts. The equation is a descriptive narrative, or story, about a specific event. The story is told from the viewpoint of atoms, ions, and molecules. The narrative, however, includes more than just a description. It also includes quantitative information about moles. The coefficients in front of each component in a balanced equation can be taken as representations of the moles of each reactant and product. The ratio of moles between each component allows for predictions of “how much is needed” and “how much can be formed.” In that sense, the mole ratio is similar to the specifics in a cooking recipe.

If two components are shown to be reacting with a balanced equation, the mole ratio between the two components dictates the quantity that must be present in order for the components to have the opportunity to fully react. If one of the components in an experiment is below the amount needed to fully react with the other component, then the deficient one is called the limiting reactant.

The reaction between baking soda (NaHCO3) and vinegar (dilute acetic acid: CH3COOH) produces CO2 and H2O. In this project, you will perform several experiments with different amounts of reactants to determine which amounts present a limiting reactant situation.

Safety Awareness: The ingredients you will use in this project are common household substances and, as such, are relatively safe to handle (do not ingest any of the substances). The small amounts of reactants in the reaction produces CO2 gas with some degree of pressure so do not exceed these amounts, and do not allow the pressure to build beyond the limits of the container. Dispose of the balloons and contents in an appropriate trash container.

Laboratory Materials List

The Projects in this course require special materials. All of the materials for this lab will need to be provided by you, the student. Before doing a project, gather all the items you will need for that specific project and out them on a clear workspace.

Student Will Supply

four rubber balloons (spherical shape) baking soda (NaHCO3)

white vinegar (Dilute acetic acid; CH3COOH) pencil

set of measuring spoons funnel

Part A – Procedure

1. Give each balloon a quick stretch and number the four balloons from 1 to 4.

2. Make a funnel from any type of paper. If you are unsure how to make a paper funnel, here is a link: http://www.wikihow.com/Make-a-Funnel-or-Cone-from-Paper

3. Into balloon number one, place one-fourth of a level teaspoon of baking soda. Place one-half of a level teaspoon of baking soda in balloon number 2. Place three-fourths of a level teaspoon of baking soda in balloon number 3, and one level teaspoon of baking soda in balloon number 4.

4. Measure 2 tablespoons of white vinegar and quickly pour it through the funnel into one of the balloons. Very quickly remove the funnel and tie off the balloon opening. Set this balloon aside.

5. Repeat procedure Step 3 with the rest of the balloons.

6. Compare the sizes of each balloon and rank them from smallest to largest volume. (Note: if the balloons are fairly spherical, you may measure their circumferences and convert those amounts to volume, or just estimate their volume from what you see.)

CALCULATIONS: Record data on chart below

Moles NaHCO3: One teaspoon of baking soda will have an approximate mass of 3.2 grams. From the molar mass of NaHCO3, determine and report the number of moles you have added to each balloon.

Moles of CH3COOH: The volume of 1 tablespoon is 15 mL. Therefore, 2 tablespoons of vinegar has a volume of 30 mL. White vinegar is approximately 5 percent CH3COOH. This means that you have added (0.05 x 30) 1.5 grams of acetic acid to each balloon. From the molar mass of CH3COOH, determine the number of moles of acetic acid you added to each balloon.

Part B- Data Organization (possible 40 points)

In column two, write in the mass and calculated moles of NaHCO3 for each of the four balloons. In column three, write in the mass and calculated moles of CH3COOH you placed in each balloon. In column four, rank the volume of CO2 gathered in each balloon. Data for each experiment will be worth 10 points each. Be sure to show all calculations and units of measurements in your responses.

Experiment Number

Moles of NaHCO3

Moles of CH3COOH

Rank of CO2 produced

1

¼ ×3.2= 0.8 g

0.8×0.011904761

=0.0095 moles

1.5= 0.0249 moles

1CO2÷1NaHCO3×0.0095

=0.0095 moles CO2

2

½ × 3.2= 1.6g

1.6×0.011904761

= 0.019 moles

1.5=0.0249 moles

1CO2÷1NaHCO3×0.019

=0.019 moles CO2

3

¾ × 3.2= 2.4g

2.4× 0.011904761

=0.0285 moles

1.5=0.0249 moles

1CO2÷1CH3COOH×0.0249

=0.0249moles CO2

4

1× 3.2g= 3.2g

3.2×0.011904761

=0.038 moles

1.5=0.0249 moles

1CO2÷1CH3COOH×0.0249

=0.0249moles CO2

Part C – Analyze (possible 60 points)

Write out the complete balanced equation for the reaction in the balloons.

Balanced equation: NaHCO3+CH3COOH CH3CHOONa+CO2H2O

Now you will be ready to draw some conclusions about your experiment. Be sure to show all calculations and units of measurements in your responses. Each question is worth twelve points.

Question 1: Which combination of ingredients (balloon 1, 2, 3, or 4) produced the greatest amount of product (CO2)?

The combination of ingredients that produced the greaest amount of product CO2 is balloon3

Calculations: 0.0249 moles of CH3COOH × (1CO2÷1 CH3COOH) =0.0249 mole CO2 = 0.56L at STP

Question 2: Which balloon(s) had NaHCO3 as the limiting reactant? Which balloon(s) had CH3COOH as the limiting reactant?

I think that balloon 1 and 2 were the two balloons who had NaHCO3 as the limiting reactant; in which the moles of NaHCO3 were than the moles of CH3COOH.

CALCULATIONS: Balloon 1= 0.0095 < 0.0249 (CH3COOH) / Balloon 2= 0.019 < 0.0249 (CH3COOH)

Question 3: Why is the amount of grams of each reactant not the proper way to determine the limiting reactant? Does any balloon illustrate this point?

The amount of grams in each reactant are not the proper way to determine the limiting reactant because the conversion of grams to moles could have smaller mass reactant, Which produces larger moles number than other reagent with larger masses.

Question 4: Why is comparing moles of reactants without using the balanced equation not the proper way to determine the limiting reactant?

Comparing moles of reactant without using the balanced equation is not the proper way to determine the limiting reactant because the elements that are present in smaller amount by mass or volume are not necessarily the limiting reactant.

Question 5: Why did one reaction situation produce the greatest volume of CO2?

One reactant situation produce the greatest volume of CO2 because the amount of moles that reactant and that needed to react were close to being the same. As balloon 3 has reagents that about equal in whole number, it produced the greatest volume of CO2. And, balloon 4 produced the same volume but made more excess NaHCO3.

Bibliography : chemistry text book

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