Stoichiometry of reactions Lab Decomposition of Baking Soda | Lab Reports Chemistry

GENERAL CHEMISTRY Name:______________________

UNIT 7: DECOMPOSITION OF BAKING SODA LAB Date:_____________Hour:_____

*Learning Target Met: Compare mass of reactants to mass of products.

Stoichiometry of reactions Decomposition of Baking Soda Lab

Introduction

You are a food chemist working for a company that makes boxed cake mix. Your company is trying to formulate

a new recipe for Black Forest cake, and every ingredient needed in the powdered cake mix has been added except

sodium bicarbonate (commonly known as baking soda). Sodium bicarbonate is used to ensure that the breads and cakes

rise during baking. Your company wants you to determine the correct decomposition reaction that baking soda

undergoes. This will help determine what quantity goes in the mix.

Materials

 Baking soda

 Stirring rod

 Pipe Stem Triangle

 Tongs

 Balance

 Wire Gauze

 Bunsen burner set up

 Crucible

Background

Due to the widespread use of sodium bicarbonate in many food products, the thermal decomposition has been

studied extensively by food chemists. Baking soda is used to prepare cakes in order to ensure that cakes rise as they

bake.

As the temperature of the cake batter reaches approximately 50⁰C, the baking soda decomposes and carbon

dioxide is released. The use of baking soda is especially popular in pancakes and waffles because the high cooking

temperatures cause the carbon dioxide to be liberated before the dough sets. Thus, the batter rises before it sets, and

we get a light and tasty finished product.

Problem

The goal of this lab is to experimentally determine which of three possible reactions is correct. All of the

equations appear to be reasonable, but only one actually occurs. On the basis of stoichiometry, you can eliminate

reactions that do not fit your experimental results when you conduct the thermal decomposition of baking soda. What

this means is, you will use stoichiometry to calculate how much carbon dioxide should be produced in each of the three

reactions, and compare those amounts to how much is actually produced by you experimentally.

Possible Decomposition Reactions:

Equation 1: sodium bicarbonate (s)  sodium hydroxide (s) + carbon dioxide (g)

Equation 2: sodium bicarbonate (s)  sodium oxide (s) + carbon dioxide (g) + water (g)

Equation 3: sodium bicarbonate (s)  sodium carbonate (s) + carbon dioxide (g) + water (g)

Safety

1. Always wear safety goggles to protect your eyes. If you get chemicals in your eyes, immediately flush them out

at the eyewash station. Let your teacher know immediately.

2. Do not heat glassware that is broken, chipped or cracked. Use tongs or a hot mitt to handle heated glassware

and other equipment because hot glassware may not look hot. Do not use tongs to transport glassware around

the room.

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UNIT 7 : DECOMPOSITION OF BAKING SODA LAB Date:_____________Hour:_____ *Learning Target Met: Compare mass of reactants to mass of products.

Stoichiometry of reactions Decomposition of Baking Soda Lab

Introduction You are a food chemist working for a company that makes boxed cake mix. Your company is trying to formulate a new recipe for Black Forest cake, and every ingredient needed in the powdered cake mix has been added except sodium bicarbonate (commonly known as baking soda). Sodium bicarbonate is used to ensure that the breads and cakes rise during baking. Your company wants you to determine the correct decomposition reaction that baking soda undergoes. This will help determine what quantity goes in the mix. Materials  Baking soda  Stirring rod  Pipe Stem Triangle  Tongs  Balance  Wire Gauze  Bunsen burner set up  Crucible Background Due to the widespread use of sodium bicarbonate in many food products, the thermal decomposition has been studied extensively by food chemists. Baking soda is used to prepare cakes in order to ensure that cakes rise as they bake. As the temperature of the cake batter reaches approximately 50⁰C, the baking soda decomposes and carbon dioxide is released. The use of baking soda is especially popular in pancakes and waffles because the high cooking temperatures cause the carbon dioxide to be liberated before the dough sets. Thus, the batter rises before it sets, and we get a light and tasty finished product. Problem The goal of this lab is to experimentally determine which of three possible reactions is correct. All of the equations appear to be reasonable, but only one actually occurs. On the basis of stoichiometry, you can eliminate reactions that do not fit your experimental results when you conduct the thermal decomposition of baking soda. What this means is, you will use stoichiometry to calculate how much carbon dioxide should be produced in each of the three reactions, and compare those amounts to how much is actually produced by you experimentally. Possible Decomposition Reactions: Equation 1: sodium bicarbonate (s)  sodium hydroxide (s) + carbon dioxide (g) Equation 2: sodium bicarbonate (s)  sodium oxide (s) + carbon dioxide (g) + water (g) Equation 3: sodium bicarbonate (s)  sodium carbonate (s) + carbon dioxide (g) + water (g) Safety

Always wear safety goggles to protect your eyes. If you get chemicals in your eyes, immediately flush them out at the eyewash station. Let your teacher know immediately.
Do not heat glassware that is broken, chipped or cracked. Use tongs or a hot mitt to handle heated glassware and other equipment because hot glassware may not look hot. Do not use tongs to transport glassware around the room.

UNIT 7 : DECOMPOSITION OF BAKING SODA LAB Date:_____________Hour:_____ “Unknown” D – A Procedure

Set up the ring stand, clamp and Bunsen burner as shown in the figure. Place the pipe stem triangle on the ring stand.
Measure the mass of the empty crucible and record its mass. [Data Table, Line A]
Obtain ≈2.00 g of baking soda from your teacher in a plastic weigh boat.
Transfer the solid material to the crucible.
Measure the mass of the crucible and baking soda and record this measurement [Data Table, Line B].
Calculate the mass of the baking soda [Data Table, Line C]. This will be your “Given” on the Post-Lab Questions.
Place the crucible directly on the pipe stem triangle.
Heat the crucible and its contents with the Bunsen burner for 15 minutes. The flame should touch the bottom of the crucible.
Use a glass rod to carefully break up any clumps that form as the heating proceeds every 5 minutes.
After 15 minutes of heating, turn off the Bunsen burner. Allow the crucible to cool for ~ 15 minutes in the pipe stem triangle.
Once the crucible is completely cooled, measure the mass of the crucible and the remaining solid material. Record the measurement [Data Table, Line D].
Determine the mass of the solid product [Data Table, Line E]. This will be the mass of the unknown that you will be comparing your stoichiometric calculations to.
Clean all apparatus and your lab station. Return equipment to the proper place. All solid material can be dumped down the sink.

Data Table

A. Mass of empty crucible (grams) B. Mass of crucible + baking soda (grams) C. Mass of Baking Soda (grams) D. Mass of crucible + product (grams) E. Mass of product (grams) “Given” B – A

UNIT 7 : DECOMPOSITION OF BAKING SODA LAB Date:_____________Hour:_____

POST-LAB APPLICATION PROBLEM

Scenario: A student adds 0.40 g of sodium hydroxide to a clean, dry 250 mL beaker and leaves the beaker on the lab table. The mass of the empty beaker is 112.58 g. After 24 hours, the student observed that the beaker contains a dry, solid white residue. The total mass of the beaker and its contents after 24 hours is 113.09 g. Following are the three possible chemical reactions that could have occurred. Write balanced equations for each. Reaction A:

sodium hydroxide (s) + carbon dioxide (g)  sodium bicarbonate (s)

Reaction B:

sodium hydroxide (s) + carbon dioxide  sodium carbonate (s) + water (g)

Reaction C:

sodium hydroxide (s)  sodium oxide (s) + water (g)

Use your knowledge of stoichiometry to determine which chemical reaction occurred. Show your work and explain your reasoning. Show work for all three reactions (mass-mass calculations for each REQUIRED). Then, apply your knowledge of what you did in the lab to analyze the scenario and identify which reaction occurred and how you know.

Stoichiometry of reactions Lab Decomposition of Baking Soda , Lab Reports of Chemistry

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Stoichiometry of reactions Decomposition of Baking Soda Lab

Data Table

POST-LAB APPLICATION PROBLEM

sodium hydroxide (s) + carbon dioxide (g)  sodium bicarbonate (s)

sodium hydroxide (s) + carbon dioxide  sodium carbonate (s) + water (g)

sodium hydroxide (s)  sodium oxide (s) + water (g)