Chem1025C-Reactions and their Driving Forces Lab

Reactions and their Driving Forces Lab

INTRODUCTION

Not all chemicals react with one another, but when a reaction does occur, some change in
the characteristics will be noted. Changes in physical characteristics give a hint to the
chemical changes occurring in a reaction. There are 4 common indications of a chemical
change:

1) Formation of a solid (which will often turn a reaction mixture opaque)
2) Formation of a gas (bubbles that can be observed and do not come from

boiling)
3) Temperature change (the test tube will be warm to the touch in the absence of

heating)
4) Color change (a change in hue, not just turning lighter due to dilution)

This lab will explore four common types of chemical reactions: combination,
decomposition, single replacement, and double replacement. These reactions can be
observed by noting a physical change in the nature of the reactants. In this lab you will
observe at least one of each type of these reactions.

A. Double Replacement Reaction

In double replacement reactions, the ions in two compounds switch. This reaction has
the general formula: AB + CD à AD + CB

Often this type of reaction is accompanied by the formation of an insoluble solid, or
precipitate, a gas, or water.

An example of a double displacement reaction is the formation of the solid silver chloride
from the mixture of two solutions: NaCl (aq) + AgNO3 (aq) à AgCl (s) + NaNO3 (aq)

B. Single Replacement Reaction

The single replacement reaction involves the displacement of one component in a
compound by another. The general formula for this reaction is: A + BC à B + AC

Single replacement reactions often involve the transfer of electrons, called an oxidation-
reduction reaction. There are four common types of chemical reactions: combination,
decomposition, single replacement, and double replacement. These reactions can be
observed by noting a physical change in the nature of the reactants.

Aluminum can replace copper from solution: 2 Al(s) + 3 CuCl2(aq) à 3 Cu(s)+ 2 AlCl3(aq)

In this case, you would observe the aluminum dissolving into the solution, and the
formation of copper metal. You may also notice the blue color of the copper (II) chloride
solution fade.

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C. Decomposition Reaction

A compound, which breaks down into elements or simpler components, is a
decomposition reaction. This reaction can be described by the general formula:
AB à A + B

An example of decomposition is the electrolysis of water into hydrogen and oxygen:

2 H2O(l) à H2(g) + O2(g)

D. Combination Reaction:

In a combination reaction two elements react (“combine”) to form a compound. This
reaction has the general formula: A + B à AB

The oxidation of copper is a good example of a combination reaction:

2 Cu (s) + O2 (g) à 2 CuO (s)

Prepare your notebook. When the lab is complete your lab notebook should include the
following:

1. Include Reaction Lab in the Table of Contents
2. Write the title of the lab on the top of the page.
3. Date/number the page (if you work on it over a few days, date each time you are

working). Sign in your lab notebook each time you stop working.
4. Record the Purpose of Experiment in your own words. Remember the purpose is the

overall question that will be answered by collecting the data and doing any
requested calculations.

5. Indicate PPE (personal protection equipment) required while performing the lab:
goggles, gloves, lab apron, and closed-toed shoes.

6. Answer the pre-lab questions in your lab notebook.
7. Prepare your notebook to record observations for each reaction by writing tables.
8. Complete the post-lab question.

PRE-LAB QUESTIONS
For each of the reactions below, classify as a combination, decomposition, single
replacement, or double replacement.
1. Mg (s) + Cl2 (g) à MgCl2 (s)
2. 2 Zn (s) + O2 (g) à 2 ZnO (s)
3. Pb(NO3)2(aq) + H2SO4(aq) à 2 HNO3(aq) + PbSO4(s)
4. NH3 (aq) + HCl (aq) à NH4Cl (aq)
5. AgNO3 (aq) + NaI (aq) à AgI (s) + NaNO3(aq)
6. AgNO3 (aq) + NaCl (aq)à AgCl (s) + NaNO3 (aq)
7. Zn(s) + H2SO4(aq) à ZnSO4(aq) + H2(g)
8. H2CO3(aq) à CO2(g) + H2O(l)
9. 2 H2O(l) à 2 H2(g) + O2(g)
10. 2 K(s) + 2 H2O(l) à 2 KOH(s) + H2(g)

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Chemical Reactions Activity:
You will observe a number of chemical reactions and record your observations. Afterwards
you will balance the chemical equation for each reaction. Remember to wear your PPE and
work safely.

Read the procedure completely BEFORE you begin mixing the reactants.

Materials needed:
Lab kit bag L04

Please read labels carefully to make sure you are using the correct substance. Ask if you
have a question.

The purpose of this experiment is to investigate several reactions. For each reaction you
will be required to make observations of the reactants (before you mix them), what
happened during the reaction (container became warm, bubbles, solution turned cloudy,
etc.), and the products (what did the final mixture look like) in your notebook.

You will be performing a total of 12 reactions – 10 from your kit and 2 as videos in
Canvas.

You will be using one of your Ziploc bags to collect the waste. Using a Sharpie write
L04 and the chemicals you will be placing in the waste Ziploc. Pour the waste into the
collection bag, seal the bag, and then rinse and dry the test tubes. Keep the test tubes for
future experiments.

A. Double Replacement Reactions

1) NaCl(aq) + CaCl2(aq) à (rinse down sink)
2) NaCl(aq) + HC2H3O2(aq)à (rinse down sink)
3) NaCl(aq) + Na2CO3(aq) à(rinse down sink)
4) CaCl2(aq) + HC2H3O2(aq) à(rinse down sink)
5) CaCl2(aq) + Cu(NO3)2(aq) à (collect waste)
6) CaCl2(aq) + Na2CO3(aq) à(rinse down sink)
7) Cu(NO3)2(aq) + Na2CO3(aq) à (collect waste)

Procedure:

1. Label the test tubes: 1-7
2. For each combination make observations about each substance before mixing .

Please note that clear is not the same as colorless. Water would be described as
clear, colorless and cherry Kool-Aid would be described as clear, red. Milk would be
described as opaque or cloudy white.

3. After you have made the initial observations, using a pipette place 5 drops of the
first substance into a test tube. Then add 5 drops of the second substance.

4. Look for the four indications of a chemical reaction stated in the Introduction.
Record your observations of any changes that occur.

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B. Single Replacement Reactions

Keep in mind that reactions with solids are much slower than reactions with two
aqueous reactants. If a reactant is a solid, let them sit for 60+ minutes before you
make your final observations.

8) Fe(s) + Cu(NO3)2(aq) à (collect waste)
9) Fe(s) + Na2CO3(aq) à(collect waste)
10) Fe(s) + CaCl2(aq) à (collect waste)

Procedure:

1. Label the weigh boats: 8-10
2. For each combination make observations about each substance before mixing.
3. Use scissors to cut a small piece of iron (steel wool type substance) and place a

sample in each weigh boat.
4. Using a pipette place 5 or more drops of the second substance on the iron.
5. Look for the four indications of a chemical reaction stated in the Introduction.

Record your observations of any changes that occurred. Keep in mind that reactions
with solids are much slower than reactions with two aqueous reactants. If a
reactant is a solid, let them sit for 60+ minutes before you make your final
observations.

6. Pour the waste into the collection bag, seal the bag, and then rinse and dry the weigh
boats. Keep the weigh boats for future experiments.

7. When you are finished with the lab be sure to remove your gloves and place them in
the waste Ziploc, wash your hands thoroughly, and clean your workspace. Keep the
waste in a secure location away from children and pets. You will return it when you
return your lab kit.

C. Decomposition Reaction (video)

11) (NH4)2CO3(s) à

D. Combination Reaction (video)

12) Fe(s) + O2(g) à

8. Complete the data tables. If no reaction was observed your products are written
as “NR”. For all combinations that result in a reaction, complete the questions
regarding the reaction.

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Data Table (example data tables shown below)
Reactants
Observations before mixing: Observations during mixing Observations after mixing

Did a reaction occur? Yes or No. If yes, then complete the boxes below. If no, write NR

Choose the best options for completing each sentence.

1) The reaction type for this reaction (single replacement, double replacement,
combination, decomposition)

2) What is the driving forces for the reaction: (formation of a solid, heat from the
formation of H2O or a weak acid, transfer of electrons in a single replacement
reaction)

Example Table for no Reaction

(1) NaCl(aq) + CaCl2(aq)

Observations before
mixing:
NaCl – clear, colorless
solution
CaCl2 – clear, colorless
solution

Observations during mixing
Both solutions came together,
did not observe any changes

Observations after mixing
clear, colorless mixture

Did a reaction occur? No

Example Table when a Reaction occurs

(6) CaCl2(aq) + Na2CO3(aq)

Observations before
mixing:
CaCl2 – clear, colorless
solution
Na2CO3– clear, colorless
solution

Observations during mixing
Mixed completely, no bubbles
or heat

Observations after mixing
white solid in a colorless
solution

Did a reaction occur? Yes

1) double replacement reaction
2) The driving force for the reaction is the formation of a solid.

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Post-Lab question
Choose three of the following chemical equations and balance them.

1. CaCl2(aq) + Na2CO3(aq) àCaCO3(s) + NaCl(aq)
2. Cu(NO3)2(aq) + Na2CO3(aq) à CuCO3(s) + NaNO3(aq)
3. Fe(s) + Cu(NO3)2(aq) à Cu(s) + Fe(NO3)3(aq)
4. (NH4)2CO3(s) à NH3(g) + H2O(g) + CO2(g)
5. Fe(s) + O2(g) àFe2O3 (s)

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