Lab 4: Types of Reactions
Objectives:
1. Observe changes in chemical and physical properties during a variety of
chemical reactions
2. Write balanced chemical equations for all reactions carried out
3. Identify type of reaction carried out (some may be more than one type)
Background:
A chemical reaction consists of reactants and products. The reactants are what
you start with (also called starting materials) and the products are the new compounds
that form during the reaction. From section 6.4 of your text chemical reactions can be
classified into four general categories: (1) Combination (2) Decomposition (3)
Displacement (single and double) (4) Combustion. These reaction types can be
represented by generic chemical equations as follows:
Combination: A + B  AB
Decomposition: AB  A + B
Single-displacement: A + BC  AC + B
Double-displacement: AB + CD  AD + CB
Combustion: A +O2  AO2 or AH4 + O2  AO2 + H2O
Within the above categories, reactions can be further categorized as precipitation or redox reactions (see Chapt 6 of text and check for charge changes). During a precipitation
reaction, an insoluble solid (precipitate) is formed as a product. A re-dox reaction
occurs when electrons are exchanged between the reactants. In addition, reactions can
be classified as exothermic (releasing heat) or endothermic (consuming heat). In this lab
you will carry out various reactions and make careful observations about what you see.
In the data report you will express them as balanced chemical equations and determine
what type of reaction has taken place.
Pre-Lab:
1. What type of reaction do you expect each to be?
2. Compare reaction 7 to reaction 8. Are they the same reaction in different
directions? How can you tell?
Safety Notes:
 Wear your safety goggles at all times
 Handle all chemicals carefully (rinse them off your skin immediately)
 Take only the amount of chemicals that you need and never put unused
chemicals back into the reagent bottle
 Discard all used or leftover chemicals in the waste containers provided (do not
pour any chemicals down the sink and do not put your rinse water in the waste)
 Clean up any spills immediately and clean up everything when finished
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Procedures:
Carry out the following reactions. For each reaction, carefully write down all
observations (color change, gas evolution, formation of a precipitate, or temperature
change) below the appropriate reaction on the pages you created for the pre-lab. Your
observations will be turned in and graded along with the data sheet.
Use clean test tubes for the reactions.
Reaction #1
Mg + O2  MgO
Procedure: Clean a Mg strip with glass or steel wool. Using tongs to hold the Mg strip,
burn the strip. Dispose the product in the solid waste container.
Reaction #2
NH4OH(aq)  NH3(g) + H2O
Procedure: Open the bottle of conc. NH4OH. Test the pH of the fumes using a wet
piece of pH paper. Do not let the paper touch the sides of the container.
Reaction #3
Mg (s) +
HCl (aq)  H2
(gas)
+
Mg2+(aq) + Cl-(aq) .
Procedure: Place a strip of Mg in 1 mL of 0.1M HCl.
Reaction #4

AgNO3(aq) + HCl (aq)
AgCl(s) +
HNO3 (aq)
Procedure: Mix 0.1M HCl with 0.1M AgNO3 in equal volumes.
Reaction #5 HCl(aq) + NaOH(aq)  H2O + NaCl(aq)
Procedure: Measure the pH of 0.1M HCl and 0.1M NaOH. Mix the two in equal volume
and stir well. Measure the pH of this mixture. Did the reaction generate heat?
Reaction #6 CO32- (aq) + H+ (aq) 
H2CO3 (aq)  H2O (l) + CO2 (g)
Procedure: Place CaCO3 (s) in 2 mL of 0.1M HCl.
Reaction #7 Cu (s) +
ZnSO4(aq)  CuSO4(aq)
+
Zn (s)
Procedure: Place a small piece of Cu (s) in 1 mL of 0.1 M ZnSO4.
Reaction #8 Zn (s) + CuSO4(aq)

Cu (s) +
ZnSO4(aq)
Procedure: Place a small piece of Zn (s) in 1 mL of 0.1M CuSO4.
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Data Sheet (To be attached to your lab report. Recopy if messy): For each reaction write the
balanced chemical equation. List all types of reaction that apply: Combination, Decomposition,
Replacement (single/double), Combustion and Redox. Record any observations such as
formation of heat, generation of bubbles or precipitation of a solid etc.
Reaction 1: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 2: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 3: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 4: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 5: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 6: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 7: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
Reaction 8: Balanced chemical equation:
Type (or types) of reaction:
Obserations:
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Lab Report Guide:
- 1. Results (5 pts)
o Data sheet neatly filled out with balanced equations, correctly identified types
of reaction and detailed observations
- 2. Post Lab Questions (5 pts)
o Typed answers to the Post Lab questions. Note that single sentence
answers will not suffice. State the answer to the question followed by a
brief description of the evidence supporting that answer.
Post Lab Questions: (Typed answers to be submitted with lab report)
1. In reaction #4, what was the solid that formed in the reaction? In reaction #3,
what gas caused the bubbling in the solution?
2. Did the reaction types match your predictions?
3. The law of conservation of mass states that the mass of the reactants should be
exactly equal to the mass of the products. When a piece of firewood burns the
mass of the ashes is much lower than the mass of the wood. Where did the
remaining mass go?
4. Where you surprised by the results of reactions 7 and 8? Why do these results
make sense? Hint reactions generally proceed from high energy to low energy
like a boulder freely rolling down a hill.
5. When iron or steel nails rust, their mass increases. Does this break the law of
conservation of mass?
Edited by Nick Buker 12/20/08
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