Types of Chemical Reactions
Background: Chemical reactions can be represented qualitatively by word equations, for example,
sulfur + oxygen yields sulfur dioxide. These descriptive equations lack quantitative significance,
however, and are not very useful in chemistry. A balanced chemical equation is a more useful way to
express the same information.
The reactants are placed to the left of the arrow and the products are placed to the right. By
applying the law of conservation of mass, the coefficients are adjusted so that equal numbers of each
element appear on both sides of the equation. The resulting balanced equation has a quantitative as
well as qualitative significance.
In this experiment you will investigate four types of chemical reactions and write balanced
equations.
Composition reactions involve the combination of two reactants to form one product:
A + B  AB
Fe + S  FeS
or
Decomposition reactions involve the separation of a compound into elements or simpler compounds:
AB  A + B
2H2O2  2H2O + O2
or
Replacement reactions involve the replacement of one element in a compound by a more active
element:
A + BX  AX + B
Cl2 + 2HBr  2HCl + Br2
or
Double replacement reactions involve the exchange of aqueous ionic species. Often a precipitate forms
or a gas is given off:
AX + BY  AY + BX
or
2KI(aq) + Pb(NO3)2(aq)  2KNO3(aq) + PbI2(s)
Objective: To become familiar with the various types of chemical reactions and write balanced
equations.
Safety: Wear chemical splash goggles. Use caution when heating objects with a Bunsen Burner. Tie
back long hair. Do not observe the burning magnesium directly!
Disposal: Dispose of waste products as directed at each station. With the exception of calcium
hydroxide, liquids are safe to go down the drain and solids are safe to go into the garbage can, but be
careful with hot material that the garbage can is not ignited.
Procedure: For each reaction, observe the reactant(s), record your observation(s), and balance the
equation.
Composition Reactions
Station 1: Using crucible tongs, heat a strip of copper foil in the inner cone of the Bunsen burner flame.
Note any changes in the copper. Allow the strip to cool and use your spatula to scrape some of the
product from the foil.
Observations: _______________________________________________________________
____ Cu(s) + _____O2(g)  _____CuO(s)
Station 2: Using crucible tongs, heat a 4cm strip of magnesium ribbon in the Bunsen burner flame. Do
not observe the burning magnesium directly. As soon as the magnesium ignites, remove it from the
flame. After the reaction has stopped, examine the product.
Observations: ________________________________________________________________
____ Mg(s) + ____ O2(g) ____MgO(s)
Decomposition Reactions
Station 3: Place approximately 1 g of sodium hydrogen carbonate (also known as baking soda) in a test
tube. Hold the tube in a test tube holder and heat gently with the Bunsen burner. Hold a burning splint
in the mouth of the test tube.
Observations: _________________________________________________________________
____ NaHCO3(s)  ____CO2(g) + ____H2O(g) + ____Na2CO3(s)
If you were to mass the remaining powder in the test tube and compare it to the starting mass,
how would the masses compare? ___________________________ Why? _______________________
Station 4: Place approximately 1 g of copper sulfate in a test tube. Hold the tube in a test tube holder
and heat gently with the Bunsen burner. Hold a burning splint in the mouth of the test tube.
Observations: __________________________________________________________________
____ CuSO4 ∙ 5H2O(s)  ____CuSO4 (s) + ____ H2O(g)
Station 5: Place approximately 1 g of copper carbonate in a test tube. Hold the tube in a test tube
holder and heat intensely for two minutes.
Observations: __________________________________________________________________
____ CuCO3 (s)  ____ CuO(s) + ____CO2(g)
Single Replacement Reactions
Station 6: Place a small clean test tube in the test tube rack. Add 5 ml of 3 M hydrochloric acid. Place a
small amount of magnesium in the tube. Invert a larger clean test tube over the reacting tube for one
minute. Light a wood splint and hold it to the mouth of the inverted tube.
Observations: ___________________________________________________________________
____HCl(aq) + ____ Mg  ____ H2 + ____MgCl2(aq)
Station 7: Place a small piece of steel wool (iron) in a clean test tube. Add 10 ml of 0.5 M copper
sulfate. Wait several minutes. In addition to watching, feel the test tube.
Observations: __________________________________________________________________
____Fe(s) + ____CuSO4(aq)  ____ Cu(s) + ____FeSO4(aq)
Station 8: Pour 10 ml of distilled water into a clean test tube. Add a small piece of calcium metal to the
tube. Test the tube for hydrogen by holding a burning splint at the mouth of the tube.
Observations: __________________________________________________________________
____ Ca(s) + ____H2O(l)  ____Ca(OH)2(s) + ____ H2(g)
What does calcium look like? ______________________________________________________
Double Replacement Reactions
Station 9: Place 2 drops of 0.1 M silver nitrate in a well. Add 2 drops of 0.1 M sodium chloride.
Observations: __________________________________________________________________
____ AgNO3(aq) + ____ NaCl (aq)  ____AgCl(s) + ____ NaNO3(aq)
Station 10: Place 2 drops of 0.1 M zinc acetate in a well. Add 2 drops of 0.1 M sodium phosphate
tribasic.
Observations: __________________________________________________________________
____ Zn(C2H3O2)2(aq) + ____ Na3PO4(aq)  NaC2H3O2(aq) + ____Zn3(PO4)2(s)
Station 11: Place 2 drops of 0.1 M sodium sulfide in a well. Add 2 drops of 3 M hydrochloric acid. Test
the odor by wafting.
Observations: _________________________________________________________________
Na2S(aq) + ____ HCl(aq)  ____ H2S(g) + ____ NaCl(aq)