Electrolytes Electrolytes Substances that dissolve in water and undergo a physical or chemical change to produce ions Nonelectrolytes Substances that do not produce ions when dissolved in water Strong vs Weak Electrolytes Strong electrolytes Essentially 100 of the dissolved substance generates ions Weak electrolytes Only a relatively small fraction of the dissolved substance generates ions Figure 11 6 Solutions of nonelectrolytes such as ethanol do not contain dissolved ions and cannot conduct electricity Solutions of electrolytes contain ions that permit the passage of electricity The conductivity of an electrolyte solution is related to the strength of the electrolyte Water and other polar molecules are attracted to ions Ionic Electrolytes The electrostatic attraction between an ion and a molecule with a dipole polar molecule is called an ion dipole attraction Water molecules surround and solvate the separated ions This physical process is known as dissociation Figure 11 7 As potassium chloride KCl dissolves in water the ions are hydrated The polar water molecules are attracted by the charges on the K and Cl ions Water molecules in front of and behind the ions are not shown Solubility of Ionic Compounds Competing forces influence the extent of solubility of an ionic compound 1 Ion dipole attraction If this is the dominate force then the compound is pulled into solution and has very high water solubility 2 The force of attraction between oppositely charged ions If this is the dominate force then the compound tends to remain un dissolved and in the solid state and have very low water solubility Covalent Electrolytes Some covalent compounds are electrolytes because they chemically react with water to produce ions Note this is not a dissociation process This is known as an ionization process Example HCl Strong acids essentially ionize to completion 100 and are therefore strong electrolytes Weak acids and bases only react partially generating relatively low concentrations of ions when dissolved in water and are classified as weak electrolytes How to Determine Whether a Substance is a Non Weak or Strong Electrolyte Is the compound ionic or molecular covalent If it is ionic then the compound is a strong electrolyte If the compound is covalent you must ask Is it an acid base or neither If the compound is a weak base then it is a weak electrolyte If the compound is neither an acid or base then it is a nonelectrolyte If the compound is an acid you must ask Is it a strong or weak acid If the compound is a strong acid then it is a strong electrolyte If the compound is a weak acid then it is a weak electrolyte