Type of chemical reaction lab

Revised 3/26/18
Types of Chemical Reactions CHM 101
Objectives
1.
To review the four basic chemical reaction types.
2.
To conduct and observe a series of experiments highlighting the 4
reaction types.
3.
To review balancing reaction equations.
Background
Most inorganic chemical changes can be classified by four common reaction types.
These include:
1.
Addition or combination reactions. Two or more substances combine to form
one product. The general formula: A + B → AB. Examples:
a.
S + O2 → SO2
b.
SO3 + H2O → H2SO4
c.
2Na + Cl2 → 2NaCl
2.
Decomposition Reactions. One substance breaks down into 2 or more
substances. The general formula: AB → A + B. Examples:
a.
CaCO3 → CaO + CO2
b.
2NaHCO3 → Na2CO3 + H2O + CO2
3.
Single Replacement (Oxidation-reduction). Reactions where one element in a
compound is replaced by another element. The general formula: A + BC → B + AC
Single replacement are always oxidation-reduction reactions where the oxidation
number of two elements change. Examples:
a.
2Na + MgCl2 → Mg + 2NaCl
b.
Zn + 2HCl → ZnCl2 + H2
c.
2KCl + F2 → Cl2 + 2NaF (anion replacement)
4.
Double Replacement reaction. These reactions involve the exchange of ions
between two compounds. The general formula: AB + CD → CB + AD. Signs of double
replacement include the formation of a solid precipitate or a gas is produced.
Examples
a.
AgNO3 + KBr → AgBr(s) + KNO3
b.
HCl + NaOH → NaCl + H2O (neutralization reaction)
c.
K2S + 2HCl → H2S(g) + 2KCl
Oxidation-reduction (redox)
In addition to being classified as one of the four reaction types some chemical reactions
can also be classified as oxidation-reduction reactions (or redox). Redox reactions
involve changes in the oxidation state of two elements in the reaction process. For
example, in this reaction: S + O2 → SO2
the oxidation number for sulfur changes from 0 to +4 while the oxygen (O2) changed from
0 to -2.
However, in this reaction: H2O + SO3 → H2SO4 no oxidation numbers changed hence it
is a nonredox reaction. More examples of redox:
a.
2Na + Cl2 → 2NaCl
b.
2KCl + F2 → Cl2 + 2NaF
Page 1 of 3
Revised 3/26/18
Double replacement reactions are never redox. However, some composition,
decomposition, and all single replacement reactions will qualify as redox reactions.
Evidences of chemical reactions
1.
Changes in acidity. Litmus paper will detect changes in acidity.
2.
Formation of a solid precipitate. If after mixing two solutions a precipitate settles
out this is an indicator of a double replacement reaction.
3.
Evolution of a gas. Gases produced during a reaction will bubble and fizz (but not
boiling).
4.
Color changes. Some solids will change color when heated. Other reactions will
produce a colored precipitate.
Procedure. Each step corresponds to an entry numbered 1-8 on the
data table.
Caution: Carry test tubes in a test tube rack at all time!!!
Label test tubes for each reaction with a sharpie.
Reaction 1. Do this reaction under a fume hood. Place a piece of zinc metal into a
clean test tube and add a few drops of 6.0 M Hydrochloric Acid (HCl).
Reaction 2. Add about 40 drops of 3% Hydrogen Peroxide (H2O2) into a LARGE test
tube. To the peroxide add a few crystals of KMnO4. Immediately, hold a
glowing splint into the mouth of the test tube to test whether the gas given
off supports combustion. The KMnO4 is a catalyst in this reaction.
Reaction 3. To a test tube, add about 30 drops of Copper(II) Sulfate (CuSO4) solution
(note its color). To the test tube place a tip of a spatula full of iron filings.
Set the test tube aside and observe changes later in the lab.
Reaction 4. Add about 20 drops of Lead(II) Nitrate (Pb(NO3)2) to a test tube. To the
test tube add about 8-10 drops of H2SO4. Swirl the contents of the test
tube for about 30 seconds and let it sit for a few minutes.
Reaction 5. Place a small amount of calcium carbonate solid (CaCO3) to a test tube.
Then slowly add 0.1 M hydrochloric acid (HCl) to the CaCO3.
Reaction 6. Place a small amount of Copper(II) Sulfate (CuSO4 • 5H2O) crystals into a
dry test tube. Gently heat the test tube, hold it with a test tube holder.
Observe the vapor condensation inside of the tube and color change of
the solid.
Reaction 7. Place 40 drops of NaOH solution into a clean test tube. Add one drop of
phenolphthalein indicator to the test. Observe any color change before
and after the indicator was added. Place 40 drops of 0.1 M HCl solution to
another test tube. Add a drop of phenolphthalein to the HCl in the test
tube. Observe any color change before and after adding the indicator.
Page 2 of 3
Revised 3/26/18
Drop wise, add the HCl acid into the test tube containing the NaOH until
you observe a color change in the test tube. Note any color change in the
test tube.
Reaction 8. Place about 30 drops of sodium carbonate (Na2CO3) solution in a clean
test tube and test its acidity with a piece of red litmus paper. If the red
litmus turns blue, the Na2CO3 solution is basic. To the Na2CO3 solution
add about 20-22 drops of 0.1 M hydrochloric acid and swirl the contents
gently. Now test the acidity of the mixture with red litmus paper.
When all the reactions have been completed, pour the contents of the test tubes and
beakers into a waste container (under one of the hoods). Wash the test tubes with soap
and place them upside down in the test tube rack.
Clean lab tables upon completion!
Page 3 of 3
Revised 6/14/17
Name __________________________Station #____________ Date ______________
CHM 101 – Types of Chemical Reactions
Pre-Lab Question
1. Describe each type of chemical reactions.
2. How do you know if a reaction is a redox reaction?
3. What are signs that a chemical reaction has occurred?
Page 1 of 1
Revised 3/26/18
Name ___________________________Station# _____________Date ________________
CHM 101 – Types of Chemical Reactions
Post-Lab Question
Balance these equations and identify the type of reaction it represents.
a)
AgNO3 (aq) + Cu (s)
→
b)
BaCl2 (aq)
+
Na2SO4 (aq)
→ BaSO4 (s)
c)
Cl2 (g)
+
NaBr (aq)
→
NaCl (aq)
d)
KClO3 (s)
→
KCl (s)
+
O2 (g)
e)
AlCl3 (aq)
+
NH4OH (aq)
→ NH4Cl (aq) + Al(OH)3 (s)
f)
H2 (g) +
O2 (g) → H2O (g)
Cu(NO3)2 (aq) + Ag (s)
+
NaCl (aq)
+
Br2 (l)
Page 1 of 1
Types of Chemical Reactions
Make-Up Data
Reaction types: composition, decomposition, single replacement, or double replacement.
Observations
1.
Formation of bubbles.
2.
KMnO4 crystals turned the hydrogen
peroxide solution into purple color then
the color disappear after stirring. The
wooden splint kept lighted on inside the
test tube for few seconds.
3. The original color of the solution was
blue. The solution’s color got faded and
copper deposited in the solution
4.
Formation of white solid (precipitation)
5.
Formation of bubbles
Reaction Type
Balanced Equation
Zn + 2HCl → _____________
2H2O2 → _________
Fe + CuSO4 → ____________
Pb(NO3)2 + H2SO4 →
______________
CaCO3(s) + 2HCl →
______________
6.
The blue crystals turned into white
powdered and water vapor were noticed
on the interior wall of the test tube.
CuSO4 • 5H2O + heat →
_________
7.
NaOH solution is colorless. The solution
turned into pink color upon adding
phenolphthalein. HCl solution is
colorless. No change in color after
addition of phenolphthalein. The NaOH
pink color disappeared after the addition
of HCl solution.
HCl + NaOH → _____________
8.
The red Litmus paper turned into blue
color after immersed in the Na2CO3
solution. Formation of bubbles were
observed upon addition HCl on Na2CO3
solution
Na2CO3 + HCl →
_______________