Chemistry: Unit 5 Outline: Stoichiometry

Name

WPHS

Chemistry

Unit 5 Packet

Stoichiometry

Bergmann-Sams

Chemistry: Unit 5 Outline: Stoichiometry

Assignment / Must be done in class
Podcast 5.1
Worksheet 5.1
Lab: Simple Weight Loss / 
Podcast 5.2 (OPTIONAL/AS NEEDED)
Worksheet 5.2

Podcast 5.3

Worksheet 5.3
Lab: Vinegar—NaHCO3 / 
Podcast 5.4
Worksheet 5.4
Lab: Limiting Reactant Exploration Lab / 
Lab: Limiting Reactant Lab / 
Podcast 5.5
Worksheet 5.5
Take Home Lab (Cookies-Optional)
Unit 5 Reviewsheet
Unit 5 Vocabulary
Lab Exam / 
Unit 5 Exam / 

Unit 5: Vocabulary

Stoichiometry

Limiting reagent/limiting reactant

Excess reagent/excess reactant

Theoretical yield

Actual yield

Percent yield

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Name

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Name

(OPTIONAL) Take Home Lab: Making Chocolate Chip Cookies Name

The following recipe for chocolate chip cookies recently appeared in Chemical & Engineering News (C&EN, Jun 19, 1995, p. 100). It was attributed to Jeannene Ackerman of Witco Corp.

Ingredients:

1 587.5 cm3 gluten

4.9 cm3 NaHCO3

4.9 cm3 refined halite

176.25 cm3 partially hydrogenated tallow triglyceride

177.45 cm3 crystalline C12H22O11

177.45 cm3 unrefined C12H22O11

4.9 cm3 methyl ether of protocatechuic aldehyde

Two calcium carbonate-encapsulated avian albumen-coated protein

473.2 cm3 theobroma cacao

236.6 cm3 de-encapsulated legume meats (sieve size #10)

To a 2-L jacketed round reactor vessel (reactor #1) with an overall heat-transfer coefficient of about 100 Btu/F-ft2-hr add one, two, and three with constant agitation.

In a second 2-L reactor vessel with a radial flow impeller operating at 100 rpm add four, five, six, and seven until the mixture is homogeneous.

To reactor #2 add eight followed by three equal portions of the homogeneous mixture in reactor #1. Additionally, add nine and ten slowly with constant agitation. Care must be taken at this point in the reaction to control any temperature rise that may be the result of an exothermic reaction.

Using a screw extrude attached to a #4 nodulizer place the mixture piece-meal on a 316SS sheet (300 x 600 mm). Heat in a 460K oven for a period of time that is in agreement with Frank & Johnston's first order rate expression (see JACOS, 21, 55), or until golden brown.

Once the reaction is complete, place the sheet on a 25ºC heat-transfer table allowing the product to come to equilibrium.

Conversion Factors

1 teaspoon = 5cm3

235 cm3 = 1 cup

ºC = 9/5ºF +32

To Receive Credit: You must have a signed note from your parent/guardian that indicates that you made the cookies –you can even bring in a sample to your friendly Chemistry Teacher.
PROBLEMS: Use dimensional analysis to set up the problem. Please show your work!

Show your work here for how much of each item you need to measure out at home:

How many cookies did you made from this recipe?

If you only have 100cm3 of unrefined C12H22O11, how much gluten will you need?

You have decided with a group of friends to make these cookies for a fund raiser. It is your job to make 1000 cookies. How many calcium carbonate-encapsulated avian albumen-coated protein will you need to buy?

Adjust the recipe for 3 calcium carbonate-encapsulated avian albumen-coated protein and determine how much of each reactant you need in the recipe.

STOICHIOMETRY LAB—Simple Weight Loss

A balanced equation indicates the proportions between reactants and products. More specifically, the coefficients in the equation indicate the mole ratios between the chemical substances. Thus, it is possible to determine how much product will be produced from a given amount of reactant. This predicted amount can then be compared with the actual amount produced to determine the percent yield of the reaction.
In this experiment, you will investigate two reactions:

Copper and aqueous silver nitrate yield silver and aqueous copper(II) nitrate.
Sodium bicarbonate and aqueous sulfuric acid produce aqueous sodium sulfate, water, and carbon dioxide gas.

SAFETY

2M sulfuric acid can cause burns. Avoid skin and eye contact. Rinse spills with plenty of water.

PROCEDURE

Obtain a beral pipet containing 2M H2SO4.
Obtain a clean, dryflask. Measure and record its mass. Place approximately 0.30g of NaHCO3 into the flask. Find the combined mass of the flask and sodium bicarbonate and record.
Determine the exact mass of sodium bicarbonate by subtraction. This mass must be between 0.20 and 0.40 g. Record the mass of sodium bicarbonate in a data table.
Record the TOTAL mass of all the components of the lab: sodium bicarbonate, flask, dropper and sulfuric acid.
SLOWLY, drop by drop, add the sulfuric acid to the sodium bicarbonate to generate carbon dioxide gas. Continue releasing the acid in this manner until gas production ceases.
Measure and record the TOTAL mass of all the components again (like in step 4).
Return the beral pipet with the remainder of the sulfuric acid. Rinse the contents of the flask down the drain with water. Clean up your lab station.

DATA

Construct a data table for each reaction to display your laboratory measurements. Make sure that each value is clearly labeled.

ANALYSIS

Write a balanced equation for the reaction.

Calculate the actual mass of carbon dioxide produced (“actual yield”).

Using the balanced equation, calculate the mass of carbon dioxide that should be produced from the mass of sodium bicarbonate that youused (“theoretical yield”).

CONCLUSIONS

Calculate the percent yield of the carbon dioxide using the equation below (show your work).

% yield = / experimental yield /  100
theoretical yield

A perfect percent yield would be 100%. Comment on your degree of accuracy and suggest possible sources of measurement error. How could these errors be reduced in the future?

Limiting Reactant Exploration Lab: How much Carbon Dioxide?

Introduction:

In this lab you will do a cool reaction, make some measurements, make a graph, and then write down some observations. The reaction that you will do is the reaction between vinegar and baking soda. In this reaction, carbon dioxide, CO2 will be produced. Chemists use chemical symbols to show the reaction. The reaction is:

CH3COOH (aq) / + / NaHCO3 /  / H2O / + / CO2 / + / NaCH3COO
Vinegar / Baking
Soda / Water / Carbon
Dioxide / Sodium
Acetate

Materials:

Apparatus as pictured below
Vinegar
Baking Soda

To simplify: Here is a picture of what you will need:

Procedure:

Follow this procedure as closely as possible.

place 0.25 g into a paper towel
Get the appropriate amount of vinegar into the flask
Set-up the apparatus—and mix.
Record the amount of CO2 collected

Data

Fill out the following data table:

Amount of vinegar / Amount of baking soda / Vol CO2
1 / 1 mL / 0.25g
2 / 2 mL / 0.25g
3 / 3 mL / 0.25g
4 / 4 mL / 0.25g
5 / 5 mL / 0.25g
6 / 6 mL / 0.25g

HAVE YOUR TEACHER SIGN HERE IMMEDIATELY AFTER COLLECTING DATA

Questions

Describe in detail what occurred (your observations) when the vinegar was mixed with the baking soda. Some descriptive words that you should probably use are, but not including (gas given off, fizzing, foaming, balloon expanding)

Describe the pattern of how much carbon dioxide, CO2 was formed as you added more and more vinegar. Relate this to the graph.

For each trial: explain which substance was the limiting and excess reagent. Explain how you were able to determine this.

You should have noticed that as you increased the amount of vinegar eventually you got the same amount of carbon dioxide, CO2. Explain why that occurred.

Chemistry

Limiting Reactant Lab

Introduction

A limiting reactants is defined as one of the reactants in a chemical reaction that will be used up first. The purpose of this lab is to determine the amount of precipitate that will be produced when a given amount of calcium chloride and sodium sulfate are mixed.

Once you have massed the calcium chloride and the sodium sulfate you will need to do each of the following before you proceed with the rest of the experiment.

Write the balanced chemical reaction noting the states of matter for all substances. (See solubility chart to determine which substance precipitates.)
Determine which reagent, calcium chloride or sodium sulfate, is limiting.
Predict the amount of the precipitate that will be produced.

Once you have done these three things, show them to your instructor. Then you may begin the experiment.

Procedure

Label and mass a test tube. The test tube must be completely dry
Obtain about 0.30 grams of each reagent (It doesn’t matter how much you get just as long as you know exactly how much you obtain), and determine both which reagent is limiting and how much precipitate you will discover.
Dissolve the calcium chloride into 3 mL of deionized water by carefull flicking the test tube (Your instructor will show you how to do this. Dissolve the sodium sulfate into 3-mL of deionized water.
Pour the sodium sulfate solution into the test tube with calcium chloride in it. Take care to get all of the sodium sulfate into the calcium chloride test tube.
Remove the stopper and then place your sample into a centrifuge and spin out the precipitate. (Caution should be used in using this device. Your teacher will instruct you on proper use of a centrifuge)
Decant, or pour off, the liquid (supernatant) above the precipitate. Be careful not to allow any of the precipitate to be poured out.
Add about 10-mL of deionized water to your precipitate and spin it again. Decant again and repeat this step two more times for a total of four centrifuges
SHOW YOUR PRODUCT TO YOUR TEACHER AND GET HIS SIGNATURE. Set your labeled test tube into a drying oven overnight.
Weigh your test tube and determine the mass of the precipitate that you have. SHOW YOUR PRODUCT TO YOUR TEACHER AND GET HIS SIGNATUREAGAIN. Compare this amount to what you expected to get from your calculations.

Calculations

Show all calculations needed to determine the expected amount of precipitate required to do the experiment. This should include the balanced chemical reaction and all appropriate stoichiometric calculations.

Questions

Why did you have to mass the test tube prior to beginning the experiment?

Why did you need to add water to the solid calcium chloride and solid sodium sulfate to cause the reaction to occur?

Comment on sources of error.

What was your percentage of error?

Draw a picture of the two test tubes prior to adding the two chemicals. What had happened to the calcium chloride? What happened to the sodium sulfate.

Now draw a picture of the test tube once you have mixed the two chemicals. Where are all of the chemicals now? Label this in your diagram.

Worksheet 5.1Stoichiometry

1. Carbon disulfide is an important industrial solvent. It is prepared by the reaction of coke with sulfur dioxide:

5C(s)+2SO2(g) -----> CS2(s) +4CO(g)

a. How many moles of CS2 form when 6.3 mol of C reacts?

How many moles of carbon are needed to react with 7.24 moles of SO2

Silver can be made according to the following equation:

___AgNO3+ ___Ca  ___Ca(NO3)2 + ___Ag

 Balance the equation

If 35.3 moles of silver nitrate are reacted how many moles of silver are produced?

Barium oxide reacts with carbon dioxide to make Barium carbonate:

___BaO + ___CO2  ___BaCO3

 Balance the equation

 If 23.4 moles of barium oxide react, how many liters of CO2 are required at STP?

Car batteries are called lead storage batteries because of their use of large quantities of lead. These batteries utilize the following equation.

Pb + PbO2 +2H+ + 2HSO4-  2PbSO4 + 2 H2O

If 34.3-g of PbO2 react how many grams of water will be formed?

Assuming the same mass of PbO2, how many grams of PbSO4 will be formed?

Ammonia, (NH3) is produced by reacting its elements with each other according to the following equation:

___N2 + ___H2 ___NH3

Balance the equation.

 If 34.3-L of nitrogen is reacted with hydrogen, how many liters at STP of ammonia will be formed?

6. 32.5-g of ZnSO4 reacts to form how many grams of BaSO4 according to the following equation. Don’t forget to balance the equation.

___ZnSO4 + ___BaCl2 ___BaSO4 + ___ZnCl2

7. When sodium metal is added to water the resulting gas, Hydrogen can often explode. How many Liters of hydrogen gas is produced when 41.2-g of sodium is dropped into water. Again, you must balance the equation in order to solve the problem.

___Na + ___HOH  ___NaOH + ___H2

8. Propane is a gas used often for backyard grills. How many Liters of CO2 is produced when 54.9-L of propane (C3H8) is burned according to the following equation. Again, you must balance the equation in order to solve the problem.

___C3H8 + ___O2 ___CO2 + ___H2O

Worksheet 5.2 More Stoichiometry

How many moles of Carbon dioxide is formed when 44-mol of CH4 is burned?

43.5-grams of barium sulfate is formed from the reaction of barium nitrate and sodium sulfate. How many moles of sodium sulfate reacted?

32.3-L of O2 is formed when KClO3 is decomposed. How many moles of KClO3 reacted initially?

__KClO3 __KCl + __O2

22.8-g of NaOH is reacted with hydrochloric acid. How many grams of water is formed?

32.5-grams of iron III chloride reacts with silver nitrate. How many grams of silver chloride are formed?

43.5-grams of copper II sulfate is reacted with barium nitrate. How many grams of precipitate are formed?

How many liters of hydrogen gas is formed when 13.5-grams of calcium reacts with sulfuric acid (H2SO4)?

Calculate the mass of silver needed to react with chlorine to produce 84 g of silver chloride.

A volume of 7.5 L of hydrogen gas was produced from the single replacement reaction of zinc and nitric acid (HNO3). Calculate the mass of zinc needed for this reaction.

How many molecules of chlorine are needed to react with 5.6 g of iron to form iron III chloride?

Worksheet 5.3 Limiting Reactants

BOX ALL ANSWERS!!

1. When 114.0 g of iron and 292.7 g of chlorine gas reacts, iron(III) chloride is formed.

a. Write a balanced equation

b. How many grams of Iron (III) chloride is formed

c. What is the limiting reactant?