Bellevue College | CHEM& 161
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Electrolytes
Electrolytes are important in the body for proper function, nerve conduction. When the supply of
electrolytes in the body is depleted due to physical activity or illness, electrolyte solutions are
administered to restore a balance of electrolytes. Athletes choose to rehydrate with drinks
containing electrolytes, such as Gatorade. Pedialyte solutions are given to children. And, saline
solutions are used in medical situations to restore a balance of electrolytes in patients suffering
from various ailments.
Electrolytes are chemical substances that when dissolved in water yield solutions of charged
particles called ions. Some electrolytes dissociate (split apart) into the ions present in the original
substance. In contrast, some substances are electrolytes even though the substance does not
originally contain ions, but instead because ions are produced via chemical reactions when the
substance is dissolved in water.
Some electrolytes dissociate or ionize completely and are called strong electrolytes. In this case,
the chemical process or reaction is considered to proceed only in the forward direction to entirely
produce the product ions (the reaction has a high equilibrium constant).
strong electrolyte ions
Some chemical processes or reactions can occur in both a forward and a reverse direction –
meaning that reactants produce products, but also products produce reactants (the reaction has a
low equilibrium constant). This scenario occurs with weak electrolytes and explains why
complete dissociation or ionization does not occur for these substances.
weak electrolyte ions
If a substance does not yield a solution of ions, it is a nonelectrolyte.
In this experiment, you will discover some properties of strong electrolytes, weak
electrolytes, and nonelectrolytes by observing the behavior of these substances in
aqueous solutions. You will determine these properties using a conductivity
probe. When the probe is placed in a solution that contains ions, and thus has the
ability to conduct electricity, an electrical circuit is completed across the
electrodes that are located on either side of the hole near the bottom of the probe
body (see Figure 1: Conductivity Probe). This results in a conductivity value
that can be read by the computer. The unit of conductivity used in this
experiment is the microsiemens per cm, or µS/cm.
You will use a vial containing the sample (instead of a beaker, as
shown). The contents of the vial will be reused by others, so it is
critical that contamination is prevented.
Make sure you rinse the probe between measurements with distilled
water (use a wash bottle). Set up a waste beaker at your station to
collect the rinses between readings. At the end of lab, you may dispose
of the contents of the waste beaker in the sink with plenty of extra water from the tap.
Figure 1: Conductivity Probe
