Learning Goals Unit 4: Copper lab, Writing formulas ... · ... Copper lab, Writing formulas, Naming compounds ... criss-cross method for writing chemical formulas based on the

Learning Goals Unit 4: Copper lab, Writing formulas, Naming compounds

I will be able to:

KNOW (define)

• Reactant and products

• Exothermic and endothermic reactions and signs of each

• The symbols (aq), (s), (l), (g), and when to use these symbols

• Precipitate

UNDERSTAND

1. Describe a chemical reaction 2. Describe five signs that a chemical change has occurred 3. Describe the following laboratory techniques: decanting, water bath and gravity filtration 4. Describe the criss-cross method for writing chemical formulas based on the fact that compounds have no overall charge.

DO

1. write a correct chemical formula (in symbols) for a compound when you are given its name in words 2. write the correct name for a compound when you are given its chemical formula (in symbols) 3. know when to include a prefix (if there are two non-metal elements) or a Roman numeral (when there is a metal with more

than one oxidation number) 4. write a correct chemical reaction, including the reactants and products

Learning Goals Unit 5: Reaction Types and predicting products I will be able to: KNOW (define)

• Define: combination, decomposition, single replacement, double replacement, and combustion of a hydrocarbon.

UNDERSTAND

1. Describe the characteristics for the five types of reaction that can be used for identifying them. DO

1. Identify the five types of reactions 2. Identify the subtypes of reaction for decomposition and single replacement 3. Predict the products of a reaction (using criss-cross and HONClBrIF)

Copper lab

Introduction: Chemical reactions are often accompanied by a formation of a precipitate, production of gas (known as evolution of gas in chemistry), change in color, or a pronounced temperature change. You will observe all these evidences for chemical change in a series of laboratory experiments that will span several days. You will begin with the copper and end with the same element, but on the way you will make it react with different compounds. You will also learn to write chemical formulas that show the changes copper undergoes during these reactions, several laboratory techniques and terminology.

Purpose:

• To recognize that production of gas, change in color, formation of a precipitate, or the evolution of heat are often associated with chemical changes.

• To study changes of copper as it goes through a cycle of several reactions.

• To practice writing proper chemical formulas, using the reactions of copper as examples.

Be very careful when working in the lab and wear goggles at all times, since you will be using dangerous chemicals.

Your teacher will show you how to dispense the nitric acid (HNO3) at the extraction hood. Take this opportunity to record HNO3 appearance in your observations section.

Changing Cu to Cu(NO3)

1. Wear goggles and closed toe shoes

2. Go to a weighting station, tare the plastic container and take approximately 1.5 g of copper. Place the Cu in a 400 ml

beaker

Write here the exact amount of copper you obtained:______________________________

3. Record Copper’s appearance in your observation section

4. Go to the extraction hood where you will carefully add 20 ml of nitric acid to the copper according to your teacher’s

instructions

5. Place a watch glass on top

6. Take your beaker to your lab table and place it over white paper. Write your observations of the reaction.

Observations

Observations before reaction Observations during and after the reaction

• Cu:

• HNO3:

• During reaction:

• After reaction:

You will continue to work with the copper nitrate in another class. Answer the following questions:

A. What evidence of chemical change did you observe? ________________________________________________

____________________________________________________________________________________________

B. Look at your classmates’ beakers after the reaction. Describe any significant difference or similarities: ____________

_____________________________________________________________________________________________

C. If the same happened in all of the beakers, why does Cu always form the same compound when mixed with HNO3?

_____________________________________________________________________________________________

SECOND DAY

We will continue working with the solution you generated last class, but before we go ahead we need to introduce several

terms. Write in the spaces below the definitions given by your teacher.

Important Terms to Know:

Endothermic:_______________________________________________

Exothermic: _______________________________________________

Reactants: ________________________________________________

Products:__________________________________________________

Precipitate: _______________________________________________

(s): ______________________________________________________

(l):_______________________________________________________

(g):______________________________________________________

(aq): _____________________________________________________

Writing chemical formulas

During our last experiment we observed the reaction written below. Write the reaction in symbols:

Pieces of copper with nitric acid, HNO3 (aq) to get copper (II) nitrate and nitrogen dioxide gas a. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq). We will now continue working with the copper II nitrate solution. Be sure to wear your goggles!

Procedure:

1) Measure 20mL of the copper (II) nitrate with a graduated cylinder and pour it on a 200mL beaker.

2) Measure 20mL of sodium hydroxide solution, NaOH (aq) from the squeeze bottle in the extraction hood and pour on a 50

ml beaker.

3) Use a strip of litmus paper to test the pH of the NaOH and record it here:___________.

4) Prepare a cold water bath for the reaction you are about to create. Use a 400mL beaker and fill it about halfway with cold

water (you will share this beaker with your lab table).

5) Place your 200mL beaker inside of the 400mL beaker so that the smaller one is surrounded by the cold water. Carefully

pour the sodium hydroxide into the copper II nitrate in your 200mL beaker, VERY SLOWLY! Use the stirring rod to mix

as you add the NaOH. Record observations of this reaction in the box.


• Cu(NO3)2:

• NaOH:


• After reaction:

6) Keep stirring until all of the NaOH has been added. Use another strip of litmus paper to test the pH of the resulting solution. If the pH does not match that of the original NaOH, add more NaOH until the colors of the pH papers match.

D. What evidence of chemical change did you observe? ________________________________________________

____________________________________________________________________________________________

E. Was the reaction an exothermic or endothermic reaction? Describe your answer: ___________________________

____________________________________________________________________________________________

F. The reaction you completed is described below. Write it in symbols:

The combination of copper (II) nitrate and sodium hydroxide yield copper (II) hydroxide and sodium nitrate.

G. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq).

For the next reaction you will work with an open flame. Collect your hair and any dangling jewelry and never leave

the flame unattended.

7) Add 100mL of distilled water to your 200mL beaker and stir.

8) Adjust your ring stand so that the ring is about half foot off of the lab table. Make sure the ring is secure and place your

beaker on it. Place a Bunsen burner underneath the ring stand and carefully light it. Stir the contents of your beaker as

you are heating it. Remove the beaker when no further color change is occurring. Record your observations.


• Cu(OH)2:


• After reaction:

H. What evidence of chemical change did you observe? ________________________________________________

____________________________________________________________________________________________

I. Was the reaction an exothermic or endothermic reaction? Describe your answer: ___________________________

____________________________________________________________________________________________h

e reaction you completed is described below. Write it in symbols:

The warming up of copper (II) hydroxide yields copper (II) oxide and water.

J. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq).

9) Gently tip the beaker to pour off the liquid and use the stirring rod to guide the liquid to a beaker below (this is called

decanting). Do not remove any of the solid!

K. What do you think is the purpose of decanting? _______________________________________________________

_____________________________________________________________________________________________

L. The reaction you completed is described below. Write it in symbols:

The warming up of copper (II) hydroxide yields copper (II) oxide and water.

M. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq).

10) Clean your lab table! Use a piece of masking tape to label your 200mL beaker with your names, and place it in the area

marked for your block. Wash, rinse, and dry all other equipment and place back at your lab table. Wipe the table clean.

Make sure to wash your hands when you are finished for today!

Third Day in the lab!

Remember that last time we ended by converting Cu(OH)2 to CuO. You ended with a precipitate of CuO in your

beakers.

1) Retrieve your beaker with the copper II oxide and wash the solid material (called a precipitate) by adding a squirt of

distilled water. Stir. Allow to settle and decant the liquid again.

2) Go to the extraction hood and 50 ml of hydrochloric acid, HCl (aq) with the squeeze bottle. Stir until clear (which does not necessarily mean colorless).


11) CuO:

12) HCl:

13) During reaction:

14) After reaction:

A. What evidence of chemical change did you observe? ________________________________________________

____________________________________________________________________________________________

B. Was the reaction an exothermic or endothermic reaction? Describe your answer: ___________________________

____________________________________________________________________________________________

C. The reaction you completed is described below. Write it in symbols:

You got copper (II) chloride in water by adding diluted hydrochloric acid (HCl) in water to copper II oxide.

D. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq).

Next reaction

3) Put a pre-cut piece of aluminum wire in the test tube so it hooks over the top and is submerged in the liquid. Record your observations.


•••• CuCl2:

•••• Al:

•••• During reaction:

•••• After reaction:

E. What evidence of chemical change did you observe? ________________________________________________

____________________________________________________________________________________________

F. Was the reaction an exothermic or endothermic reaction? Describe your answer: ___________________________

____________________________________________________________________________________________

G. The reaction you completed is described below. Write it in symbols:

The combination of copper (II) chloride with the aluminum wire produced a diluted solution of aluminum

chloride and a precipitate of copper.

H. Now circle the reactants, and put a square around the products. Remember to label each reactant and product as

(s), (l), (g), or (aq).

4) When the reaction is done (bubbling stops), shake off the copper from the aluminum wire, decant and discard the

liquid, and rinse the copper with distilled water.

5) For each bench-top, fill a 250 ml beaker with over 200 ml of deionized water and place the beaker on a hot plate.

Turn the hot plate to medium (around 200 F).

6) Set-up a ring-stand and place a funnel in the ring. Position your 400ml beaker below the funnel.

7) Get one 12.5 cm circle of filter paper. Mass the filter paper at one of the weighing stations and write this mass here:

Mass of my filter: ______________

8) Fold your filter paper in half (the paper should look like a semi-circle). Now fold the paper in half again (the filter

paper should now look like a quarter of a circle). Holding the paper so that the curved end is toward you, open up the

paper so you have a little cup.

9) Place the filter paper in the funnel, making sure that you really do have a “cup.”

10) Add a little of the hot distilled water to your original beaker, swirl, and then carefully pour the solution into the funnel.

11) Add 50 ml of the hot distilled water to the funnel, and allow gravity to “rinse” the precipitate. This process is called

“gravity filtration.” Once this has filtered, repeat this rinse with an additional 50 ml of hot distilled water.

12) Make sure to turn off the hot plate when you have finished!

13) Get a small squeeze bottle of acetone (this is like nail polish remover) to do two final rinses. Use two or three good

squirts of acetone to rinse off all of your precipitate, allow to drain, then do this again. When you are finished,

carefully take your filter paper out of the funnel, and place it on a piece of brown paper towel. Congratulations, you

have just completed the conversion back to copper! Your instructor will tell you where to leave your final product.

Make sure to write your names on the brown paper towel.

14) Clean up your area completely! Wash your hands!

Final Day of Copper Conversions: How Much Did We Get?

Now that our final product has had a chance to dry, we will weigh the copper we recovered and see how it compares

with the amount we started with.

1) Find your group’s filter paper filled with copper. Carefully take it to one of the weighing stations, find the Mass of the Copper and Filter Paper, and record it

Mass of the filter with copper: ____________.

2) Go back to step 7 from the last class, where you recorded the mass of the filter paper. You will use this to calculate the mass of the copper you recovered.

Mass of Filter Paper Alone: _____________

Mass of Cu(s) = (Mass of Cu(s) + Filter Paper) – (Mass of Filter Paper Alone)

Your Mass of Cu(s) = _________________ - ______________________ = ___________________

3) Place your copper in the area marked for your section, and clean your lab table. Now you are ready to analyze the results of your copper conversions!

Data analysis

1) Percent recovery is a term used by chemists to describe how much of a compound is recovered following a series of

reactions compared to the original amount. Go back to your observations from the first day of the copper lab to find your

original amount of copper:

Original amount of copper ________

You will use this number and the mass you just measured at the end of the lab to calculate percent recovery.

Percent recovery === 100________________100 xxCu

Cu

initial

final

2) Look back at the series of procedures you completed. Explain why your percent recovery of copper is not 100%. In other

words, give at least 2 examples of steps where a loss of copper may have occurred.

3) Use your observations to complete a drawing of the cycle that the copper went through. It should have these features:

(ID20.3)

Each arrow represents a reaction. At the end of the arrow is the copper product that was made along with its state

(s, l, g, aq). Alongside each arrow put the ingredients that you added to the test tube and their state. Lastly, along

each arrow write the main observation you made.

Chemical formulas for compounds

In the copper lab you mixed copper with nitric acid to produce the new compounds: copper (II) nitrate and nitrogen dioxide. Since it is too

long to write the name of all of these compounds, chemists developed a symbolic way of writing all this in an easier-to-read way.

Cu + HNO3 Cu(NO3)2 + NO2 + H2O

We call this expression a chemical formula. The left side of the formula is called the reactants and the right side the products.

Today we will focus on how to write the formula for one single compound, and later we will see how to write the whole chemical formula.

You have seen chemical formulas many times before, but you probably have not stopped to think what they mean. Here are other

examples that you might have encountered; try to identify the compounds:

• H2O ___________________________

• CO2 ___________________________

• C6H12O6 ___________________________

Now that you know the symbols of at least 43 elements you can tell what elements make up a given compound, but

• Do you know what do the subscripts mean?

• Do you know what determines the specific value of the subscript?

• Could H2O sometimes be HO2? How about H3O2?

It turns out that H2O will always be H2O. The subscripts mean something very important. Subscripts in a chemical formula indicate

the number of atoms of a given element in a compound. When an element has no subscript it means it has only one atom: For

example:

H2O has 2 atoms of hydrogen and one atom of oxygen

Indicate the number of atoms for each element in a compound

1. CO2 ____________________________________________________________________

2. C6H12O6 ____________________________________________________________________

3. NaCl ____________________________________________________________________

The question becomes, what determines the value of the subscripts? Let us see if you can figure it out given the following information..

Fill in the oxidation numbers for the last example.

I. H2O Oxidation numbers are: H +1, O -2

II. NaCl Oxidation numbers are: Na +1, Cl -1

III. MgF2 Oxidation numbers are: Mg +2, F -1

IV. Al2S3 Oxidation numbers are: Al +3, S -2

V. Be3P2 Oxidation numbers are: Be ___, P ___

Oxidation number is the charge the ion that is formed as an atom gains or loses electrons to become more stable by having its s and p sublevels full.

Describe with words any observed pattern: _________________________________________________________________________

___________________________________________________________________________________________________________

Subscripts in a chemical formula are determined by the oxidation numbers of the elements. You should be able to find any element’s

oxidation number by looking at their position in the periodic table. Here is a reminder on where do oxidation numbers come from.

Examples:

Here are the steps to follow to write the formula for a compound:

Example: Determine the formula of the compound that contains sodium and chlorine.

1. First, draw the atomic sketch for each atom in the compound.

Magnesium Chlorine

2. Then draw the electron-dot symbols for each element. The valence (outer shell) electrons are the

ones involved in forming the bonds that hold the compound together.

Magnesium Chlorine

3. Determine how many electrons will be lost or gained by each atom. In other words, how many

electrons will be lost or will need to be gained to have a completely filled s and p sublevels? Then

determine the oxidation number of each element.

Magnesium Chlorine

4. Find the appropriate puzzle pieces that have the same oxidation number as the two ions in the

compound. Find the amount of pieces you need for each so that the number triangles on each +

piece are equal to the number of spaces on each – piece.

Magnesium Chlorine Together (Compound)

5. Finally, write the formula with element symbols and subscripts. Remember that the subscripts

must not have a sign.

Here is your opportunity to write the chemical formula of the compounds generated when we combine chemically different

elements: Provide the formula of the new compound by finding their oxidation numbers, either using the method outlined

above, or by the element’s placement in the periodic table. Use the puzzle pieces and always write the cation before the

anion.

A. lithium and chlorine

B. magnesium and oxygen

C. barium and chlorine

D. potassium and nitrogen

Fill in the following chart based on the steps for writing chemical formulas.

Write the group # the ions are in

on the periodic table

Charges the Ions will have Drawing of puzzle pieces

for cations and anions

Total Charge for each

element

Balanced Formula for this

compound

Sodium Fluoride

Gain e- / lose e

- Gain e

- / lose e

-

and how many and how many

Na F

Na F

Copper II Oxide

Gain e- / lose e

- Gain e

- / lose e

-


Cu O

Cu O

Potassium Nitride

Gain e- / lose e

- Gain e

- / lose e

-


K N

K N

Calcium Phosphide

Gain e- / lose e

- Gain e

- / lose e

-


Ca P

Ca P

Writing Chemical Formulas—Criss Cross Method

Now that we have looked at how compounds trade electrons, wouldn’t it be nice if there was a quicker and simpler

way of determining the formula that does not involve puzzle pieces? Relax—there is!! It is called the “criss-cross”

method. Here’s how it works.

1. Look at the name and determine the ions in the compound by looking at their placement in the periodic table or

the Table of Common Oxidation Numbers on the back of the periodic table you were given. The cation ion

(positive ion) is written first, then the anion (negative ion).

2. Write the ion symbol, and then write the oxidation number of the ion to the upper right of the symbol. You’ll find

the oxidation number listed at the top of each column.

3. Draw a around the oxidation number. The box will make life easier for you later!

4. Now, look at the two oxidation numbers. If they add up to zero, you are done. Just re-write the symbols of the

ions without the oxidation numbers (remember to write the cation first, then the anion).

5. If the two oxidation numbers don’t add up to zero, take the oxidation number of the cation (without the + sign)

and place only the number as a subscript after the anion. Now take the oxidation number of the anion (without

the - sign) and place only the number as a subscript after the cation. Re-write the symbols of the ions this time

without the oxidation numbers. If the subscript is a one (1) you do not need to write it down.

Sometimes, these ions themselves are made of more than one atom or element. We called these ions polyatomic (many

atoms). Treat them as a single ion. Whenever you write a polyatomic ion, always put the entire ion in parenthesis. If you

need a subscript, write it outside the parenthesis.

1. sodium chloride

Na Cl Add the charges: +1 + -1 = 0 done

Write the Formula: NaCl

2. magnesium phosphide

Mg P Add the charges: +2 + -3 = -1 go to step 5 & criss cross

Write the Formula: Mg 3 P2 (notice the subscripts)

3. zinc sulfide

Zn S Add charges:

4. copper II fluoride

Cu F Add charges:

Elements in the d and f blocks can have more than one oxidation number. We use roman numbers to indicate the

oxidation number: Examples: Cu I is +1, and Cu II is +2

box

Practice Writing Formulas with the Criss-Cross Method

Use the examples and steps we worked on in class to write these chemical formulas.

1. copper I bromide

2. copper II bromide

3. magnesium oxide

4. iron III sulfide

5. mercury II phosphide

6. chromium II bromide

7. aluminum fluoride

8. potassium nitride

9. zinc sulfide

10. manganese nitride

Even More Practice with the Criss-Cross Method

Use the examples and steps you have learned to write these chemical formulas.

11. potassium chromate

12. magnesium nitrate

13. copper I phosphate

14. copper II phosphate

15. ammonium sulfate

16. beryllium phosphate

17. aluminum carbonate

18. iron II dichromate

19. iron III dichromate

20. radium phosphide

Practice makes perfect! The third round of writing formulas!

Remember to show your steps with oxidation numbers.

1. silver bromide

2. calcium iodide

3. calcium oxide

4. aluminum oxide

5. silver nitrate

6. ammonium bromide

7. sodium chromate

8. magnesium phosphate

9. lithium sulfite

10. chromium III chlorate

11. aluminum nitride

12. iron II sulfate

13. iron III sulfate

14. lead bromide

15. potassium fluoride

Naming chemical compounds

Now that you know how to write a chemical formula given the name of a compund, you need to know how to go backwards and

name a compound given its chemical formula.

You know how to write a formula for: Magnesium Phosphate Mg+2 (PO4)-3 therefor it is: Mg3(PO4)2

How would you write the name for: Cu(CrO4)?

Here are some steps that can help you name different compounds:

I. Write the name of the first element or first polyatomic ion

a. If the first element is a metal:

Indicate the oxidation number of the metal with a roman numeral after the name of the element

b. If the first element is not a metal: Specify the number of atoms of the second element according to the table:

Prefix Number of atoms

Mono 1

Di 2

Tri 3

tetra 4

penta 5

Hexa 6

Hepta 7

Octa 8

II. Write the name of the ion of the second element or polyatomic ion.

Not all metals need the Roman numeral to specify the oxidation number, only those that can have more than one oxidation number.

Alkali and Alkaline Earth metals (groups I and II) do not need the Roman numerals. Check the back of the periodic table to see if a

certain metal needs it, or just add it to be safe to any metal.

Example: Mg3P2

I. Write the name of the first element: Magnesium

a. Magnesium is a metal in the second column so we do not need the roman numeral, but we can add it: II

II. Write the name of the ion of phosphorous: phosphide

Answer: Mg3P2 is Magnesium II phosphide

Example: CO

I. Write the name of the first element: Carbon

b. Carbon is a non-metal. There is only one atom of oxygen, so we write: mono

II. Write the name of the ion of oxygen: oxide

Answer: CO is Carbon monoxide

Example: CO2

I. Write the name of the first element: Carbon

b. Carbon is a non-metal. There are two atoms of oxygen this time, so we write: di

II. Write the name of the ion of oxygen: oxide

Answer: CO2 is Carbon dioxide

Example: Cu(CrO4)

I. Write the name of the first element: Copper

a. Copper is a metal. We need to find the oxidation number, since copper can be +1 or +2.

Find the oxidation number of the polyatomic ion next to copper. From the back of your periodic table is -2.

Since the compounds must be neutral and there is only one atom of copper, Cu must be +2. Write: II

II. Write the name of the polyatomic ion (look for it in the back of your periodic table): Chromate

Answer: Cu(CrO4) is copper II chromate

Example: (NH4)3(PO3)

I. Write the name of the first polyatomic ion Ammonium

No need to add roman numeral, since ammonium is not a metal, but no need to add a prefix either, since

ammonium is not a non-metal element. Notice that ammonium is the only polyatomic cation.

II. Write the name of the polyatomic ion (look for it in the back of your periodic table): Phosphate

Answer: (NH4)3(PO3) is Ammonium phosphate

It is your turn to practice. The following exercises have been broken down in categories. The first set has compunds with a metal

element and no polyatomic ions. The second set includes polyatomic ions, the third set corresponds to only non-metals, and the last

section has a mix of all types.

Metal with non-metal

1. MgO

2. CaI2

3. NaCl

4. AuO

5. Cr2O3

6. Mn3N2

7. Potassium Phosphide

8. Zinc Bromide

9. Mercury II Iodide

10. Aluminum Oxide

Polyatomics

1. Na(NO3)

2. Ni(ClO3)2

3. Cu(NO3)2

4. (NH4)P

5. Ba(Cr2O7)

6. Zn(C2H3O2)2

7. Silver hydroxide

8. Ammonium Acetate

9. Iron III sulfate

10. Lead phosphate

Two non-metals

1. SO2

2. CO2

3. CF4

4. CO7

5. NF3

6. carbon monofluoride

7. carbon trichloride

8. silicon hexaoxide

Mixed

1. K3N

2. Fe2(CO3)3

3. Sn(Cr2O7)

4. (NH4)2(SO4)

5. Ag2(SO3)

6. NO3

7. Li(OH)

8. SF6

9. C I4

10. Pb(C2H3O2)2

11. BaCl2

12. Cs3P2

13. Sr(NO2)2

14. Cr(SO4)

15. Zn3(PO4

Use the steps for naming compounds to draw a concept ma that could help you remember how to name compounds

Identification of elements, ions and compounds

It is important when working in the lab to distinguish between elements, compounds and ions, so you will practice their

identification. Let us first define these concepts first, and then you practice.

Element:

Examples of Elements:

Ion:

Examples of Ions:

Diatomic:

Examples of Diatomic:

Compound:

Examples of Compounds:

Ion:

Examples of Ions:

Practice identifying elements, compounds, and ions:

Label each of the following formulas as : element, compound, and ion:

1. H2O ________________________

2. CO2 _______________________________________

3. Mg _________________________

4. H2 __________________________

5. H+1 _________________________

6. HNO3 _______________________

7. (NO3)-1 ______________________

8. Co _________________________

9. CO _________________________

10. (NH4)+1 ______________________

11. NH3 _________________________

12. Cu(NO3) _____________________

13. Fe2O3 _______________________

14. Fe __________________________

15. Fe+3 _________________________

16. Cl2 __________________________

Chemical Change Lab - Five Fabulous Reactions!

Today you will observe different types of chemical reactions to review the evidence for chemical change and solidify some

ideas seen on the Copper lab. The goals of the lab are:

• Describe evidence of chemical change for each reaction

• Define exothermic and endothermic reactions, as well as precipitate

• Observe different types of chemical reactions

• Each lab bench has different reactions.

You and your group will move from station to station and will follow the directions written on each table. You will be asked to

A. describe the evidence for chemical change that you observe, and

B. write the number of reactants involved in the reaction and their type (two elements, one element and a compound...)

Do not forget to:

1. Wear safety goggles (on your eyes) the entire time! You are working with dangerous chemicals!

2. No horseplay whatsoever will be tolerated! This is your only warning.

3. Tie long hair back—we will be using fire and don’t want your hair to become part of the reactions.

4. Wash all glassware before and after using it. Then return it to its proper place.

5. Put no solids into the sink. Unless your teacher tells you otherwise, only rinse liquids down the sink. Paper

towels go into the trash (not into the recycling bin) when you are finished. Use the fewest paper towels that you can.

Station 1A

Reaction: Mg + O2 MgO

1. Describe the evidence for chemical change you observed:

_____________________________________________________________________________________________

_____________________________________________________________________________________________

2. How many reactants are present and what type of reactants _____________________________________________

3. How many products are present and what type of products ______________________________________________

4. Is the reaction exothermic or endothermic? Explain your answer: _________________________________________

5. Indicate if a precipitate formed: ___________________________________________________________________

Station 1B

Reaction: Fe + O2 Fe2O3


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 2A

Reaction: Pb(NO3)2 + NaCl PbCl2 + Na(NO3)


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 2B

Reaction: Pb(NO3)2 + KI PbI2 + K(NO3)


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 3A

Reaction: NH4)Cl + Na2(CO3) NH4)2(CO3) + NaCl


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 3B

Reaction: CaCl2 + Na2(CO3) Ca(CO3) + NaCl


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 4

Reaction: Cu + Ag(NO3) Ag + Cu(NO3)2


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Station 5

Reaction: C6H14 + O2 CO2 + H2O


_____________________________________________________________________________________________

_____________________________________________________________________________________________





Ideas to discuss after doing the lab:

Describe the evidences you saw for chemical change: _______________________________________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

What type of reaction is this?

There is what appears to be an infinite number of reactions we can make in the lab. The amazing thing is that they follow

predictable patterns that allow scientists to classify the thousands and thousands of reactions in five types. The great thing is

the predictability of the classification, since it will help us predict the products of a given reaction.

Let us see if you can come up with classification of reactions that scientists use. We will start by sorting sixteen reactions in

four types.

Please get a packet of Reaction Cards from your teacher. Work in a group of 2 or 3. Your mission is to sort the cards into 4

groups that share common traits, looking especially at the reactants (remember: reactants are the ingredients of a reaction).

Clues that will help you:

-how many reactants are there?

-what types of reactants are there? (elements, ions, or compounds)

- how many products are there?

Once you have decided how to arrange your cards into 4 groups, write the characteristics for each group or type, and have

your teacher check your answers.

Type 1:

# of reactants:

Type(s) of reactants:

# of products:

Type of products:

Type 2:

# of reactants:


# of products:

Type of products

Explaining each reaction

Once you have finished classifying your cards and checked them with your teacher, describe in general terms what happens

to the reactants in each type of reaction as they turn into the products, and propose a name for the reaction based on your

explanation. You can use letters to summarize as in the example below

Type 3:

# of reactants:


# of products:

Type of products

Group 4:

# of reactants:


Type of products

Reaction type 1: Name: Combination Symbols: A + B AB

In this reaction there are two reactants and only one product. The reactants get together (combine) to

produce only one compound

Reaction type 3. Name: Symbols:

When reactants


When reactants…


When reactants

Practice identifying types of reactions

Write the type of reaction for the following chemical reactions

_____________1. Al + S Al2S3

_____________ 2. Au2O3 Au + O2

_____________ 3. H2 + N2 NH3

_____________ 4. NaF Na+ F2

_____________ 6. Ca3N2 Ca + N2

_____________ 7. Zn + HNO3 H2 + Zn(NO3)2

_____________ 8. LiOH + H2SO4 Li2SO4 + H2O

_____________ 9. Cl2 + NaI NaCl + I2

_____________ 10. Al + N2 AlN

_____________ 11. K + H2O KOH + H2

_____________ 12. AgNO3 + AlCl3 AgCl + Al(NO3)3

_____________ 13. CH4 + O2 CO2 + H2O

_____________ 14. Fe2(CO3)3 Fe2O3 + CO2

____________ 15. Cr + H2SO4 H2 + Cr2(SO4)3

Classify the types of reaction from the five fabulous reactions.

Product prediction

How can classifying reactions help you predict products? We need to look at a few more details before doing that, since some

types of reaction are subdivided into subtypes.

I. Composition or combination reactions

A + B AB

Element + element Compound

Prediction: Write the same elements in the reactants as the products and do the criss-cross.

Example:

Fe + O2 Fe2O3

(The product above is rust, by the way!)

II. Decomposition

AB A + B

compound element + element

compound element + compound

compound compound + compound

Subtypes of decomposition reactions

You need to memorize the products that each of the following decomposition reactions produce so you can predict

what a given decomposition reaction will produce

A. Electrolysis of binary compound

A binary compound is a compound made up of exactly two elements.

Examples: NaCl, MgO, H2O

Compound element + element

A compound is split into individual elements. Electrolysis is used in many industrial processes in order to

produce individual elements that are normally found as compounds in nature. For example, electrolysis is used to produce Al

by separating it from its ore, Al(OH)3.

Prediction: simply write each individual element as a product. Do not forget to put a subscript 2 on the diatomic

elements! N2, O2, F2, Cl2, Br2, I2, H2

AB A + B

Examples:

NaCl Na + Cl

H2O H2 + O2

B. Heating of a metallic chlorate: a compound containing a metal and a ClO3- ion

Metal chlorate metal chloride + oxygen

A metal chlorate always splits into a metal chloride and oxygen, no matter what the metal is.

Prediction: Write the metal chloride and oxygen

m(ClO3) mCl + O2 where m= metal

Examples:

K(ClO3) KCl + O2

Mg(ClO3)2 MgCl2 + O2

Potassium chlorate is a common ingredient in fireworks and safety matches. It is also commonly used in the

lab in order to produce oxygen gas, which is otherwise expensive to get.

Heating a metallic carbonate: a compound made of a metal and a CO3 - ion

Metal carbonate metal oxide + carbon dioxide

A metal carbonate always splits into a metal oxide and carbon dioxide, no matter what the metal is.

Prediction: Write the metal oxide and carbon dioxide

m(CO3) mO + CO2 where m= metal

Examples:

Na2(CO3) Na2O + CO2

Ca(CO3) CaO + CO2

Remember, Ca(CO3) is used to make cement!

C. Heating a metallic hydroxide: a compound made of a metal and a OH- ion

Metal hydroxide metal oxide + water

A metal hydroxide always splits into a metal oxide and water, no matter what the metal is.

Prediction: Write the metal oxide and water

m(OH) mO + H2O where m= metal

Examples:

Na(OH) Na2O + H2O

Ca(OH)2 CaO + H2O

Metal hydroxides are sometimes heated and used to clean industrial equipment, since they can dissolve fats

and grease.

D. Heating an acid: a compound of a H+ ion and an anion

Acid nonmetallic oxide + water

An acid always splits into a nonmetallic oxide and water.

Prediction: Write the nonmetallic oxide and water

Acid nO + H2O where n is a non metal

Examples: heating of nitric acid

HNO3 NO2 + H2O

Strong acids are often used to clean iron and steel products, like cars, before they are sold.

III. Single replacement

Element + compound element + compound

A + BC B + AC when A is a metal

A + BC C + AB when A is a nonmetal

An element and a compound produce a different element and a different compound. Not every element will be able to

replace another one in a compound, as we will see later when we see the Activity series. For the moment we will

assume that the single element will replace the one in a compound. It is important to notice that:

a. A metal always replaces a metal

b. A non-metal always replaces a non-metal, especially if both are halogens

c. A metal can replace hydrogen in acids and water

Prediction: Check the activity series to see if the single element can replace the one in the compound. If it can,

exchange a metal by a metal and nonmetal by nonmetal, except when hydrogen is part of the compound (water or an

acid). In this case replace the hydrogen by a metal.

Examples:

Al + CuCl2 Cu + AlCl3 A metal (Al) replaces a less reactive metal (cu)

Cl2 + NaI NaCl + I2 A nonmetal (Cl) replaces a less reactive nonmetal (I)

Zn + HNO3 H2 + Zn(NO3)2 A metal (Zn) replaces H in an acid

Na + H2O Na (OH) + H2 A metal (Na) replaces H in an water

IV. Double replacement or exchange

AB + CD AD + CB

compound1 + compound2 Compound3 + compound4

Two different compounds produce two other compounds. The cation of the first reactant combines with the anion of

the second compound, and the anion of the first reactant ends with the cation of the second compound

Prediction: Write the cation of one reactant with the anion of the other reactant and do the criss-cross. Then write

the anion of the first reactant with the cation of the second reactant and do the criss –cross again.

.

Example:

AgNO3 + AlCl3 AgCl + Al(NO3)3

Since:

Cation of first reactant: Ag+1

Anion first reactant: (NO3)-1

Cation of second reactant: Al+3

Anion of second reactant: Cl-1

V. Combustion of a hydrocarbon

Hydrocarbon + oxygen carbon dioxide + water

Hydrocarbons are used as fuels: petroleum, oil, and natural gas are hydrocarbons.

This reaction is easy to predict. The products always include water and carbon dioxide. The reactants should be a

hydrocarbon (a compound with hydrogen and carbon) and oxygen. In fact, every time you hear the word burning in

chemistry you should assume that oxygen is combined with another element or compound.

Prediction: Just write CO2 + H2O as the products. Remember that you should add O2 as a reactant when you see the

word burning.

CnHm + O2 CO2 + H2O

Example:

C4H10 + O2 CO2 + H2O

Practice Reaction Type and Predicting the Products

For each of the following:

a. Determine the TYPE of reaction by looking at your Reaction Type Sheets and write the type in the space

provided. Explain why the reaction is what you chose in the space provided.

b. Determine the formulas of the reactants and the name and the formula(s) of the products, and write them in the

spaces. Remember the diatomic elements. Really think about the products.

The first one is an example.

The reaction of fluorine and sodium chloride is a Single replacement by more active non-metal .

Explanation Both chlorine and Fluorine are non-metals (halogens)

Reactant(s) formula(s) F2 and NaCl

Product(s) formula(s) Cl2 and NaF

Product(s) names the element chlorine and the compound sodium fluoride

Whole equation: F2 + NaCl Cl2 + NaF

1. The reaction of aluminum and sulfur is a reaction.

Explanation

Reactant(s) formula(s)

Product(s) formula(s)

Product(s) names

Whole equation:

2. The heating of gold (III) oxide is a reaction.

Explanation



Product(s) names

3. The reaction of hydrogen and nitrogen is a reaction.

Explanation



Product(s) names

Whole equation:

4. The electrolysis of sodium fluoride is a reaction.

Explanation



Product(s) names

Whole equation:

5. The burning of pentane, C5H12, is a reaction.

Explanation



Product(s) names

Whole equation:

6. The decomposition of calcium nitride is a reaction.

Explanation



Product(s) names

Whole equation:

7. The reaction of zinc and nitric acid is a reaction.

Explanation



Product(s) names

Whole equation:

8. The reaction of lithium hydroxide and sulfuric acid is a reaction.

Explanation



Product(s) names

Whole equation:

More practice predicting products

Follow the instructions for previous exercises

1. The heating of magnesium chlorate is a reaction.

Explanation



Product(s) names

Whole equation:

2. Potassium reacting with water is a reaction.

Explanation



Product(s) names

Whole equation:

3. Silver nitrate reacting with aluminum chloride is a reaction.

Explanation



Product(s) names

Whole equation:

4. The burning of methane, CH4, is a reaction.

Explanation



Product(s) names

Whole equation:

5. The heating of ferric carbonate is a reaction.

Explanation



Product(s) names

Whole equation:

6. The reaction of copper and nitric acid is a reaction.

Explanation



Product(s) names

Whole equation:

7. The heating of cupric hydroxide is a reaction.

Explanation



Product(s) names

Types of Reactions

Combination: A + B AB

Two atoms (or polyatomic ions) come together to form a compound

Decomposition: AB A + B:

A compound or polyatomic ion is broken down into its individual elements

Single Replacement: A + BC B + AC

An atom replaces the cation (+ part) of a compound to form a new compound and an element.

Double Replacement: AB + CD AD + CB

This reaction starts with two compounds as reactants and yields two new compounds as products. Each of the

cations changes places and recombines with the anion of the other compound.

Combustion of a Hydrocarbon:

A hydrocarbon is a compound made of only carbon and hydrogen atoms. When a hydrocarbon is burnt, it combines

with oxygen from the air and always forms water and carbon dioxide as products.

Examples: 2H2 + O2 2 H2O

Examples: CO2 C + O2

Examples: Zn + 2 HCl ZnCl2 + H2

Examples: AlCl3 + 3 Li(OH) Al(OH)3 + 3 LiCl

Examples: CH4 + O2 CO2 + H2O

Flow chart for identifying chemical reactions

1 Reactant

Type of Reaction:

Decomposition!

Check reactant to

determine subtype of

decomposition:

*binary compound

*metallic chlorate

*metallic carbonate

*metallic hydroxide

*acid

2 Reactants

1 Element & 1

Compound

Is the element O2 AND is

the compound a

hydrocarbon?

2 Compounds

Type of Reaction: Double

Replacement

1 Product

Type of Reaction:

Combination

If YES, Type of

Reaction:

Combustion of

Hydrocarbon

If NO, Type of

Reaction: Single

Replacement

Decomposition subtypes

When there is only one reactant

Single replacement Two reactants, one element and one compound

Does the reactant

have a Chlorate,

ClO3?

Does the reactant

have a Carbonate

CO3?

Is the reactant an

acid, HnY?

Is the reactant a

binary, AB?

Does the reactant

have a Hydroxide,

OH?

m(ClO3) mCl + O2 m(CO3) mO + CO2 m(OH) mO + H2O AB A + B HnYOm YO + H2O

Is the single element

a metal or a halogen?

The metal replaces a metal

m1 + m2B m2+ m1B

The halogen replaces a halogen

h1 + Ah2 h2+ Ah1

ALWAYS!

Check for criss cross, and

Diatomic elements

Practice Quiz! Cu Lab, writing formulas and naming compounds

1. Explain the difference between an endothermic and an exothermic reaction.

__________________________________________________________________________________________________

__________________________________________________________________________________________________

2. Give the meaning of the following symbols:

(aq):

(s) ______

(l) ________________________________

(g) __________________________

3. Describe at least 4 signs you observed during the Copper Cycle lab that told you a chemical reaction had taken place.

4. Describe how to decant and explain why you used this technique.

______________________________________________________________________________________________________

_________________________________________________________________________________

5. Describe how to use a water bath and explain why you used this technique.

______________________________________________________________________________________________________

_____________________________________________________________________________________________________

6. Describe how to use gravity filtration and explain why you used this technique.

______________________________________________________________________________________________________

_____________________________________________________________________________________________________

7. For the following, write the formula of the substance indicated:

a. Sulfur difluoride

b. Sodium hydroxide

c. Bromine gas

d. Barium acetate

e. Iron (III) phosphate

f. Calcium iodide

g. Cobalt (II) chloride

h. Hydrogen peroxide

8. For the following, write the name of the substance indicated:

a. CuOH

b. (NH4)(NO3)

c. CCl4

d. CaI2

e. Pb

f. Fe2O3

g. SeBr2

h. K3(PO4)

9. Write the chemical formula for the reaction described below.

a. Circle the reactants and square the products:

b. Use the symbols (s), (l), (g) and (aq)

Hydrochloric acid is diluted with water and then added to a precipitate of copper II oxide. The product was copper (II) chloride

solution.

Documents

Learning Goals Unit 4: Copper lab, Writing formulas ... · ... Copper lab, Writing formulas, Naming compounds ... criss-cross method for writing chemical formulas based on the