REACTIONS AND SOLUBILITY
The concepts in this experiment are also discussed in sections 4.5 – 4.7 of
Chemistry – A Molecular Approach
, by Tro.
This experiment is divided into two parts. Students should work individually.
In Part A you will prepare aqueous solutions consisting of acids, bases, or salts, and in Part B
observe the results of mixing these solutions together.
From your observations you will report
which mixtures yield a reaction and write a balanced chemical equation, list the spectator ions
involved in the system, and write a net ionic equation.
In Part C you will be given the same solutions you used in Part B; however, in numbered bottles.
You will attempt to identify each unknown solution by mixing it with the other unknowns and
comparing your observations to those obtained in Part B.
Reactions can be categorized into five different classes:
synthesis, decomposition, single-
displacement, double-displacement and combustion.
It is useful to classify reactions in this way
because it can assist you in the prediction of products.
For example, if a reaction has only one
reactant, it is likely to be a decomposition reaction; knowing this, you can predict the possible
An example of each of the categories is given below.
In a synthesis reaction, multiple reagents come together to form a single product.
One of the most important examples of a synthesis reaction is the fixation of nitrogen (equation
1), which is used to make commercial fertilizers.
+ 3 H
A decomposition reaction is the reverse of a synthesis reaction; a single reactant
is broken down in to two or more products.
In a previous experiment, you carried out the
decomposition of copper(II) sulfate pentahydrate through a process called dehydration. Another
example (equation 2) is a decomposition reaction used in explosives and fireworks.
A single displacement reaction involves a more reactive element displacing
a less reactive one.
, zinc is much more reactive than copper; therefore, it replaces
the copper(II) ion in cupric chloride.
A double displacement reaction involves the exchange of the anions and
cations of two compounds.
A reaction takes place between compounds AB and XY; AB and XY
are usually aqueous ionic compounds (or acids) consisting of aqueous ions (A
). When a double displacement reaction occurs, the cations and anions switch partners, resulting
in the formation of two new ionic compounds AY and XB.
This type of reaction usually results in
the formation of a precipitate, a gas, or water.