Lab 6: Properties of Compounds in Solution
Properties of Ionic and Molecular Compounds in Solution
Describe how ionic and molecular compounds dissolve in water
Use electrical conductivity to classify solutions as containing electrolytes or nonelectrolytes
Compare the electrical conductivity of substances in the pure solid or liquid state to their
conductivity in solution
Establish a relationship between electrolyte concentration and conductivity
Quantitatively prepare a solution of a given concentration and use it to perform a series of
When two or more elements chemically combine, they form a
. Compounds are generally
classified by what type of bond holds together their constituent atoms.
, which form when one or more electrons is transferred from one species to another.
compounds always contain one type of
(positively charged species) and one type of
(negatively charged species).
These cations and anions combine in such a way so that the total positive
charges cancel out the total negative charges, resulting in a neutral compound overall.
often consist of a metal cation and a nonmetal anion, though one or both of these may be replaced by a
An ionic compound is often referred to as a
(Note that this is a broad term that
does not just refer to the compound we know as table salt, a particular ionic compound.)
, which form when one or more pairs of electrons is shared between
Covalent bonds generally occur between two or more nonmetal atoms.
Ionic and molecular compounds can be distinguished by their differences in several physical properties
including melting point, boiling point, solubility, and electrical conductivity.
In this lab we will focus on
using electrical conductivity measurements to differentiate between ionic and molecular compounds.
To illustrate the difference between ionic and molecular compounds in solution, let us consider two
Table salt and sugar are both compounds that dissolve fairly easily in water.
their similarities in appearance, however, there are some important differences between the solutions that
result when these two compounds dissolve in water.
Salt, or sodium chloride (NaCl), is an ionic
compound that consists of sodium cations (Na
) and chloride anions (Cl
When sodium chloride
dissolves in water, it separates into individual cations and anions.
This process is called
The individual ions are free to move around in the solution, and since electricity is the movement of
charged particles, the solution therefore conducts electricity.
The more ions in solution, the better it will
Compounds that dissociate nearly 100% and produce a large number of ions in
solution are called
Common types of strong electrolytes include soluble salts, strong
acids, and strong bases.