C A L I F O R N I A I N S T I T U T E O F T E C H N O L O G Y

PASADENA, CALIFORNIA

CHEMISTRY 3AGeneral Information and Experiments

Chemistry 3A Experiments

Experiment Time Points

Project Pyro 3 hrs 100

Construction of a Roman Candle

Project Glow 6 hrs 200

Kinetics and Mechanism of Ru(bpy)32+

Project Ester 6 hrs 300

Synthesis of Aspirin

Project Werner 9 hrs 400

Synthesis of Cobaltammine

Characterization of Cobaltammine

Website

This lab manual, lecture notes, and TA contact information can be found on the

Chem 3A website: http://chemlabs.caltech.edu/wiki/ch3a:home

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EXPERIMENT 1A Simple Demonstration of Pyrotechnics

Historical BackgroundChemical knowledge has been used throughout history in the extraction of

crucial elements from ores, the synthesis of medicine, the molding of plastics into a

variety of lightweight materials, and many other amazing processes. These

processes are all very useful, and without them our lives would be dramatically

different, but often they are not dramatic themselves. One of the most ancient and

dramatic uses of chemistry is the manipulation of fire in its many forms.

Fireworks were believed to be first used in China in the 7th century, where they

were used in a variety of cultural celebrations. Early use was primarily limited to

noise markers with light as a byproduct. By the ninth century fireworks were so

commonplace in China that they were sold by street venders for individual

purchase and used in both family celebrations and dramatic imperial productions.

We most often see a fireworks display on the 4th of July or following a

professional sports event; an explosion of red, yellow, and blue showering down

from the skies accompanying a patriotic soundtrack is commonplace. The

elaborate displays compete with one another to be the highest, largest, and most

original. It is now common to see a single firework explode in a burst of green,

followed by red sparks, or any other color and effect combination. In recent years

fireworks manufacturers have manipulated the packing structure of fireworks to

have individual devices explode into simple shapes like stars and hearts.

Many of us can still remember a time when our parents were permitted to

purchase fireworks and set them alight in front of our homes on the 4th of July. In

order to reproduce that thrill, and to teach you a couple of the most basic chemical

reactions, we will construct our own firework.

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Chemical Background

You will design and build your own Roman Candle using some very simple

chemical knowledge, common lab materials, and a few salts & elements found in

the chemistry storeroom. In doing so, you will learn about three of the most

common chemical reactions: oxidative combustion, decomposition reactions, and

double replacement reactions.

The basic chemistry behind all fireworks is combustion (burning). Burn the

right chemicals at the right time and you will get a beautiful display. But just how

do you control that burn? Combustion requires three things: fuel, oxygen, and an

ignition source. In order to control combustion, we must control the input of at

least one of these “ingredients” to the reaction. Doing so will give us some control

of the reaction.

Equation 1. Basic combustion equation of generic organic mater. Fuel and oxygen combust to give carbon dioxide (the oxidized product) and water (the reduced product). Combustion of metals is also possible (as we will see), where the elemental metal is oxidized and combines with oxygen.

In the above reaction, control of either oxygen or the spark will control the

reaction. This can be seen in the simple action of lighting a match. At any given

moment a match stick (fuel) is exposed to the air (oxygen); it is only after a person

strikes the match against the box producing a spark does the reaction have all three

components to proceed and combustion begins. We will preform a more

sophisticated version of this combustion reaction for our Roman Candle.

A Roman Candle is a device which burns an intensely hot and bright flame of

different colors in a sequence. In order to achieve the intense hot flame we need to

not only use a good fuel, but we must augment the reaction with extra oxygen. We

will supply this oxygen with a decomposition reaction.

CH2O(s ) +O2(g)Spark⎯ →⎯⎯ CO2(g) + H2O(g)

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Equation 2. The decomposition of potassium chlorate to produce potassium chloride and

molecular oxygen. We will use this oxygen to fuel our Roman Candle. This reaction has a large activation energy which we must supply.

When potassium chlorate is heated the chlorate decomposes into chloride and

oxygen gas. By taking advantage of the extra oxygen supplied by the

decomposition of potassium chlorate, our combustion will be intense enough to

burn any metal or salt added to the Roman Candle. But how will we safely

(remotely) overcome the activation energy?

We will use another important chemical reaction to get the spark, the double

replacement (displacement) reaction. In a double replacement reaction, the ions of

two ionic compounds exchange with each other to form two new compounds.

There are many examples of these throughout chemistry, an acid-base reaction is a

specific type of double replacement reaction, where an acid and base react to form

water and a salt. We will use a double replacement reaction involving potassium

chlorate (again) with sulfuric acid.

Equation 3. The double replacement reaction between sulfuric acid and potassium chlorate to produce chloric acid and potassium sulfate (unbalanced). This reaction is driven to completion due to chloric acid’s explosive nature in the presence of organic matter.

In this reaction the liquid sulfuric acid dissolves the potassium chlorate, then the

potassium and hydrogen cations exchange to form a new acid (chloric acid) and a

salt, potassium sulfate. The production of chloric acid is the key result. Chloric acid

is explosive when it comes in contact with organic matter (careful!) Therefore, if we

have a mixture of potassium chlorate and an organic material (sugar) and add a small

amount of sulfuric acid, we will get a spark, Eq. 3. That spark will decompose the

remaining potassium chlorate producing ample oxygen, Eq. 2, which can combust

the remaining sugar, Eq. 1, resulting in the intense flame we desire.

KClO3(s )Heat⎯ →⎯⎯ KCl(s ) + 32O2(g)

KClO3(s ) + H2SO4(l ) HClO3(aq) + K2SO4(aq)

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In order to achieve colorful flames, we add a variety of salts and elements

which combust giving off different colors. Just as hydrogen gives off a specific set

(spectrum) of colors when its electrons relax from their excited to ground state

(Oxtoby, Gillis, and Campion, page 151), different metals each have a unique

spectrum. This spectrum of colors is mostly seen as a single color, for instance the

combustion of elemental iron to an iron oxide gives a yellow color, even though

the spectrum has multiple color bands. An image of the iron emission spectrum

can be found on the Chem 3A website.

The excitation of electrons results from the combustion of metals to their

oxides, or the decomposition of salts to simpler products. The combustion of

elemental metal results in a metal oxide, (the oxidation state of the metal can vary

but generally takes the most stable form, Eq. 4).

Figure 4. Combustion of metals results in a metal oxide, with a metal oxidation state which is most stable. For aluminum, the ionic oxidation state is always +3, for copper the most stable oxidation state for the ion is +2.

Salts do not combust, rather, they decompose in a predictable way. In general,

metal salts decompose into either a metal, metal oxide, or a simpler salt. Metal

chlorides decompose into the elemental metal and molecular chlorine gas. Metal

carbonates decompose to their metal oxide and carbon dioxide (Eq. 5).

Equation 5. The decomposition of a generic metal oxide. The CO32- ion decomposes into ionic oxygen and molecular carbon dioxide. The oxygen remains with the metal forming a metal oxide. The metal does not change oxidation states.

We can explain this phenomenon by looking at the electronic structure of the

carbonate ion (Fig 1). The lone ion evenly distributes electron density between the

three oxygen atoms, and away from the central carbon, figure 1a. When a positive

4Al(s ) + 3O2(g) → 2Al2O3(s )

2Cu(s ) +O2(g) → 2CuO(s )

MCO3(s ) → MO(s ) +CO2(g)

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ion, such as the metal comes in contact with the carbonate, the electronic

distribution favors the oxygen nearest the metal, figure 1b.

This weakens the C-O bond between

the oxygen nearest the metal and

strengthens the ionic bond between the

metal and oxygen. When heated, the

ion can split at this C-O bond forming a

carbon dioxide molecule and a

thermally stable metal oxide.

Metal nitrates behave in a similar

manner. Group 2 nitrates and LiNO3

decompose to a metal oxide with

nitrogen dioxide and molecule oxygen

(Eq. 6a). The remaining group 1

nitrates decompose into a metal nitrite

and molecular oxygen (Eq. 6b).

Figure 1. The electronic structure of the

carbonate ion. (a) A majority of the electron

density is evenly distributed around the outside

oxygen atoms. (b) When a metal ion nears, the

electron density shifts towards the cation.

Equation 6. Group 2 nitrate decompose into the thermally stable metal oxide, resulting in the evolution of nitrogen dioxide and molecular oxygen. Lithium nitrate behaves in this manner; however, the other group 1 nitrates decompose into metal nitrite and molecular oxygen.

2M (NO3)2(s )Heat⎯ →⎯⎯ 2MO(s ) + 4NO2(g) +O2(g)

2MNO3(s )Heat⎯ →⎯⎯ 2MNO2(g) +O2(g)

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We will use the combustion of metals in their elemental or salt forms to design

unique flames for the Roman Candle. Table 1 has a list of metals which you may

wish to use in your Roman Candle as well as the colors associated with them.

Metal Color Useful FormAntimony Glitter Sb2O3

Barium Green BaCl2

Calcium Orange CaCl2

Copper Blue-Green CuCl2

Iron Yellow FeLithium Red Li2CO3

Magnesium White MgPotassium Purple KNO3

Sodium Yellow-Orange NaNO3

Strontium Red Sr(NO3)2

Table 1. The metals in the above table will give off a variety of colors, you can use any three of these in your Roman Candle. The final column is used to determine how much colorant is needed in the potassium chlorate-sugar mixture.

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PrelabRead page iv of this manual’s introduction and complete the prelab.

1. Construct a table within your lab notebook, with rows (or columns)

representing each chemical used and columns (or rows) for: molecular mass,

density, melting point, and boiling point. Fill out the needed information for

each chemical.

2. Read the procedure below, add a column (or row) for moles used, and then

calculate the masses (or volumes) needed for each chemical to be used.

3. Add one additional column (or row) for any material safety data sheet

(MSDS) cautionary handling notes.

4. Outline the procedure in your notebook such that you will not have to refer

to this manual while you are in the lab.

Questions

5. Write a balanced chemical reaction for the combustion or decomposition of

a. Ethanol

b. Octane

c. Iron

d. Iron (III) Chloride

e. Iron (II) Carbonate

f. Iron (II) Oxide6. Write a balanced chemical reaction for the reaction of:

a. Sodium hydroxide with hydrochloric acid

b. Sodium nitrate and potassium chloride

c. Silver nitrate and iron (II) chloride

7. Write a balanced chemical reaction

a. Iron with aqueous copper (I) nitrate

b. Magnesium with aqueous nitric acid

c. Copper with aqueous hydrochloric acid

8. Calculate the volume of hydrogen gas produced when 2 g of Zn is added to 5

mL of concentrated HCl. State all assumptions.

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ProcedureCollect two test tubes. Pour 3-4 mL of concentrated hydrochloric acid (HCl) in

one test tube. Invert a second test tube over the first, leaving a small space

between the two tubes. Mass out and then carefully drop about 1g of zinc into the

HCl, closing the space between the test tubes to collect the gas. After collecting

gas for about a minute (keeping the top tube inverted as to not let the gas escape),

you may ignite the gas with an open flame.

Collect the watch glasses and a test tube from your drawer. Lay the watch

glasses out inside your hood, and clamp the test tube to one of the vertical bars at

the rear of the hood. Mass out 0.5 g each of potassium chlorate (KClO3) and sugar.

Grind these two chemicals separately and place the powders in separate watch

glasses. Add about 2 mL of H2SO4 to the test tube. It is important to label

chemicals. Use your pen and lab tape to mark either the containers or counter top

where they lie. You may also place a white napkin under the watch glasses to

make the resulting colors stand out better. ① Use your spatula to place a small

scoop of KClO3 into an empty watch glass. Use your small (2 mL) pipette bulb

and one of the disposable pipettes on your station’s shelf to add a small amount of

sulfuric acid (H2SO4) to the top of this small amount of KClO3. You may add more

H2SO4 if you need. Record your procedure and observations in your notebook. ②

Place a small amount of sugar into an empty watch glass. Add a small amount of

H2SO4 to the top of the powder, record the procedure and results. ③ Place small

equal parts KClO3 and sugar into an empty watch glass. Mix the powders gently

with the end of your spatula. Add one drop of H2SO4 to the top of the mixed

powders. ④ You may repeat this experiment if you wish, adding an equal amount

of a colorant to the mixture.

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Roman Candle

Begin your Roman Candle by assembling the hardware structure. Fill a 400

mL beaker with sand and insert a test tube into the center of the sand-filled beaker.

In a mortar and pestle grind 0.1 mol of potassium chlorate (KClO3), followed

separately by 1.5 x 10-2 mol of sugar. Mix these two chemicals in a new beaker

and set them aside for later use. Do not grind theses chemicals together due to the

risk of fire!

Choose three colors (chemicals) to include in your Roman Candle and the order

in which you would like them to burn. The possible colors and the chemicals needed

can be found in Table 1. As an example, I will describe the procedure used for a

Roman Candle first burning yellow (iron), followed by blue (copper (II) chloride),

and finally red (strontium nitrate). Starting with the last chemical to burn, mix 5 x

10-3 mol strontium nitrate and ¼ of the potassium chlorate-sugar mixture in a small

beaker. Using a piece of weighing paper or powder funnel pour this mixture into the

test tube embedded in the sand. In the same manner, mix 5 x 10-3 mol of copper (II)

chloride with ¼ of the potassium chlorate-sugar mixture and pour it into the test tube,

on top of the strontium mixture. Next, mix 5 x 10-3 mol of iron powder with ¼ of the

potassium chlorate-sugar mixture and add it to the top of the test tube. Lastly, add

the remaining potassium chlorate-sugar mix to the test tube.

Tell your teaching assistant or instructor when your Roman Candle is completed.

The majority of the Roman Candles will be set off at 10:30PM during the Wednesday

night section on the Beckman Institute Lawn. The T.A.’s will direct you to the place

and time if there are changes.

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1st Weekly Assignment (10 points)

Throughout Chem 3A, at the conclusion of each week, you are required to

submit figures which represent the work accomplished during that week (Due the

Friday following the experiment at 4 PM). This week’s assignment will be an

introduction to this activity. Due Friday Oct. 12 at 4 PM

1. Write a balanced reaction for the production of chloric acid within the Roman Candle.

2. Write a balanced reaction for the production of oxygen within the Roman Candle.3. Write a balanced reaction for the combustion or decomposition of the metals and salts

you used as colorants within the Roman Candle.4. Illustrate a figure showing the construction of your Roman Candle.

Each figure, equation, table, or plot turned in must be computer generated and

include a detailed figure caption. A proper caption will contain three elements:

1. A title. This will look like: “Figure 1. Balance equation for the reaction between

hydrochloric acid and sodium hydroxide.”2. An explanation. Explain to the reader why the plot is important. This should be one

sentence. If you are not sure what to write, perhaps the figure isn’t important enough to include.

3. Key point. Explain to the reader what should be taken from the material presented.

This is a second or third sentence describing the important or curious points of the figure. Be concise and direct with these points. Any further explanation can be discussed in the body of your report.

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Final Report Grading Scheme (50 Points Possible)

Scientific reports contain 5 parts: abstract, introduction, results, discussion, and

conclusion. Throughout the term you will write experimental reports following

this format. It is hoped that repeating this task will lead to exceptional report

writing. The pages that follow are designed to guide you throughout the report

writing format. Please refer to them throughout the term if you have questions.

Reports should be structured in the order listed below; however, you should not

write it in this order. The most important sections are the Experimental/Data and

Discussion sections, begin your report on the Experimental/Data section in order to

fully understand the data you have, then move onto the Discussion section. Spend

the vast majority of your time on these two sections. Next work on the Conclusion

and Abstract sections, which are very similar in structure. Finally, write the

introduction.

1. Abstract - 1 paragraph

A brief conclusion of the experiment so the reader knows what to expect from the report. Generally, it is structured in 3-5 sentences and uses very specific results and conclusions. Avoid general statements like the results were “good”, “positive”, or “large”, actually state the numerical result. Finally state the actual result or conclusion, the reader will want to know if your paper is worth reading.

2. Introduction - 1 pageThe most difficult section to write. (Work on this last.) A proper introduction

relates the past advances in the field to the reader complete with citations (style of citation is unimportant in our case). It should outline the major work done and the gaps in knowledge or technology. The introduction should also introduce key facts that the reader must know to understand the paper. Items such as, electron structure, general reaction scheme, important chemical or physical properties, and why these are important to know. Lastly, it should tell the reader what your experiment does to address the questions in the field.

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3. Experimental / Data (Results) - Length will vary, needs to be complete

The Data section need not have much written language, but it needs to describe the experiment and present all your data in a clear effective manner. This is where all your raw data goes, use lots of tables and figures. Brief statements of the data may or may not be required. Many people are uncomfortable with a section with few words and many tables etc, so they combine it with the Discussion section. I feel this is a mistake.

4. Discussion - Length will vary, needs to be completeThe discussion section is the most important section in a science paper. This

is the section where you explain all your data. You should have processed data within this section. For example, if you have a series of standard and sample data plotted in the data section, the discussion section will have the analysis of those samples and comparison to the standards. You will state why you did any calculations (not how) and what the result means. Please do not do a sample calculation, do state the equation you used to calculate the result, (we will assume your algebra is correct). Results should be recorded in a table. Draw conclusions and state the results in positive specific terms, as in the abstract, avoid relative language- it is vague.

5. Conclusion - 1 - 2 paragraph(s)The conclusion needs to summarize the data and discussion without restating

them. State the major points of the processed data and end results of any calculations you made. State specific results and why they are important. Make sure you have a final positive statement summarizing and concluding your paper and the experiment you conducted.

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The first task you must complete before you write a report is to understand your

data thoroughly. The best way to do this is to plot your data in a meaningful way.

You have already done this by constructing figures after last week’s experiments.

The second step is to outline your thoughts in order to convey your story.

Although sometimes tedious, outlines can greatly help the flow and efficiency of

your message. The last step is to fill in the outline with your story’s details. For

this first report, I will provide the outline, you will use it to write only the results

and discussion sections. (Due on Friday Oct. 19 at 4 PM).

Follow the outline below (and on the next page):

I. ResultsA. Experimental Procedures

1. Write a brief description of each experimenta. Zn + HClb. KClO3 +H2SO4

c. Sugar +H2SO4

d. KClO3 +Sugar + H2SO4

e. Roman Candle2. Include a diagram of experimental set-up, if you believe it would help.

B. Observational Results1. Write your observations from each experiment.2. Add photos, if you took them.

The experimental observations may be written directly following each experimental description.II. Discussion

A. Zn +HCl1. Write the complete and balanced reaction involved2. Discussion the reaction.

a. Address driving force behind the reaction.b. Calculate the theoretical volume of gaseous product.c. Address the reaction for the combustion of the product.

i. Write the complete and balanced reaction.B. Roman Candle Chemistry

1. KClO3 + H2SO4

a. Write the complete and balanced reaction involvedb. What kind of reaction is this?c. What are the products, why are they important?

2. Sugar + H2SO4

a. Generally, what happens to the sugar?3. Watch glass - KClO3 + Sugar + H2SO4 & Roman Candle

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a. Write the complete and balanced reactions involvedb. Why is this equilibrium reaction driven to completion?c. In your own words describe the sequence of reactions which

ignited your Roman Candle, starting with the drops of acid and ending with the final layer of material.

4. Colorantsa. What three colorants did you use?b. Write the complete and balanced reaction for combustion of each

metal or decomposition of each salt in your Roman Candle.c. For each metal, find the emission spectrumd. What color did you observe?e. Discuss the difference between the color observed and emission

spectrum.

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