Introduction

We all need electrolytes in our diet. Why? Electrolytes are used by our nerves and muscles. Among other things, they regulate our blood pressure and pH of our blood and help keep our tissues hydrated. As the name implies, in many cases, electrolytes are involved with carrying electrical current in our bodies. During exertion we can lose electrolytes through sweating, which is why athletes commonly drink beverages high in electrolytes.

Electrolytes are salts and molecules that ionize to some extent. Strong electrolytes completely ionize while weak electrolytes only partially ionize. Nonelectrolytes do not ionize at all. We can classify compounds as strong, weak, or nonelectrolytes by measuring the conductivity of these chemical solutions. 

Strong Electrolytes

Strong electrolytes are usually ionic compounds; they can be expected to dissociate 100% in aqueous solution.

Example:  MX(s) → M+(aq) + X(aq)

States of matter are expressed as (s) for solid, (aq) for aqueous (dissolved in water). Some substances may be liquid (l) or gas (g) in their native, pure form.

Weak Electrolytes

Weak electrolytes are molecules that can partially dissociate, depending on their strength. Acids ingested as part of our diets are a common example of weak electrolytes in our diets. Some fraction of the molecules of these compounds will dissociate into ions which may then recombine to form the original molecule.

Example:  HA(l) ⇄ H+(aq) + A(aq)  (<100% dissociation)

Nonelectrolytes

Nonelectrolytes are molecules that usually do not dissociate to form ions. Even though many dissolve in water, the resulting solutions do not conduct electricity very well at all. Contamination may result in higher readings than anticipated for these substances.

Example:  MA(s) → MA(aq)

In this experiment you will analyze the components of a popular sports drink used by athletes  to replenish electrolytes and water lost during physical activity.

Objectives

  • Write equations for the dissociation of compounds in water.
  • Use a conductivity probe to measure the conductivity of solutions.
  • Determine which molecules or ions are responsible for the conductivity of solutions.