Electrolytes and Non-Electrolytes

ELECTROLYTES AND NON-ELECTROLYTES CONCEPT An ionic or electrovalent compound that conducts electricity in molten (fused) or aqueous (solution) state can be classified as an electrolyte. They can be divided into acids, bases, and salts, because they all give ions when dissolved in water. When an electrolyte conducts electricity, chemical changes occur and the electrolyte decomposes into its component element at the electrodes. Examples of electrolytes are dilute acid solutions, dilute alkaline solutions, molten salts or aqueous salt solutions. These solutions conduct electricity due to the mobility of the positive and negative ions, which are called cations and anions respectively. However, if the compound is unable to ionise it does not conduct electricity it is called a non-electrolyte. In general, the extent to which an electrolyte can break up into ions categorises an electrolyte. This gives a measure of the degree of dissociation (a) of an electrolyte. Based on this degree the electrolytes can be classified as strong or weak electrolyte and non-electrolyte. Metals which are conductors not regarded as electrolytes because they are not decomposed by the passage of an electric current. Strong electrolytes - completely ionize to form freely ion when dissolved, and no neutral molecules are formed in solution. The more the availability of freely ions in an electrolyte, the greater is its capacity to carry or conduct current. For example, NaCl, HNO , HClO , and CaCl are strong electrolytes. The ionization can be represented by, 3 3 2 NaCl(s) → Na (aq) + Cl (aq) + - Since NaCl is an ionic solid (s), which consists of cations Na and anions Cl . No molecules of NaCl are present in NaCl solid or NaCl solution. The ionization is said to be complete. The solute is one hundred percent (100%) ionized. Some other ionic solids are CaCl , NH Cl, KBr, CuSO , NaCH COO (sodium acetate), CaCO , NaHCO (baking soda). + - 2 4 3 3 4 3 A weak electrolyte ionizes or dissociates only partially to form freely ions. Some neutral molecules are present in their solutions. For example, ammonia, NH OH, carbonic acid, H CO , acetic acid, CH COOH, and most organic acids and bases are weak electrolytes. When the number of freely ions is less in an electrolyte, the lesser is its capacity to carry or conduct current. The following ionization is not complete. The example of reaction is; 4 2 3 3 Water is also a very weak electrolyte. The ionization of pure water can be represented by the ionization equation, H O → H + OH 2 + - A non-electrolyte is a chemical compound which does not conduct electricity in any state. It does not provide ions in a solution and therefore current does not flow through such solution. Examples of non-electrolytes are covalent substances such as naphthalene, latex, and sugar solution. Example of sodium chloride (NaCl) in molten and aqueous solution. UNIQUE FEATURE OF THIS ACTIVITY a) This simulation can attract student become more focus while studying on this topic. b) The multimedia illustrations help students to visualize the reaction that happen in the ionization of the electrolytes. c) Helps students to more understand about the properties of electrolytes and non-electrolytes. EMPOWER a) Electrolytes are substances that produce ions in solution. b) Substances can be categorized as strong electrolytes, weak electrolytes or nonelectrolytes. c) The electrical conductivity of any substance is based on the movement of charged particles. 1. 2. In metals, electricity is conducted by freely moving electrons. In electrolytes, electricity is conducted by freely moving ions: positive ions and negative ions. When the meter is switched on, QUESTION: a) What is meant by the term electrolyte? Give two examples of electrolytes. b) State the difference between a conductor and an electrolyte. c) Explain why solid magnesium is a non-electrolyte, but becomes an electrolyte when it is in the molten state. ANSWER: a) An electrolyte is a chemical substance that conducts electricity in the molten state or in aqueous solution and undergoes chemical changes. The examples of electrolytes are molten lead(III) chloride, and aqueous potassium iodide solution. b) A conductor can conduct electric current. An electrolyte can conduct electric current as well as be decomposed by electricity. c) Solid magnesium oxide consists of positive ions and negative ions held together by ionic bonds. The ions are not free to move and hence cannot conduct electricity. In the molten state, heat energy has overcome the ionic bonds. The ions are freely moving and hence able to conduct electricity.