Electrolytes Acids, Bases & Salts

An electrolyte is a substance that will conduct electricity, WHEN DISSOLVED IN WATER . The electrical conductivity of a solution is a measure of its ability to allow an electrical current to flow through it.

Covalent substances do not dissociate when they are dissolved in water Electrolytic dissociation is the separation of a dissolved compound into two ions of opposite charge Ionic substances dissociate in water because of the polar nature of the water molecules. E.g. NaCl Covalent substances do not dissociate when they are dissolved in water E.g. sugar

The Strength of Electrolytes The strength of an electrolyte is the degree to which it dissociates into ions. The higher the degree of dissociation, the stronger the electrolyte. NaCl is a strong electrolyte because many ions are formed Initial Conditions 100 molecules After dissolution 100 ions

Initial Conditions 100 molecules After dissolution 90 molecules Acetic acid is a weak electrolyte because few ions are formed sugar is a non-electrolyte because no ions are formed Initial Conditions 100 molecules After dissolution

The strength of the electrolyte depends on it’s nature and it’s concentration

Types of Electrolytes An acid is a substance that releases H+ ions in an aqueous solution Fruit juices, soft drinks, vinegar, and gastric juices are all acids The have a sour taste Litmus paper turns red in an acid

The formula for an acid usually begins with an “H” (e. g. HCl) The formula for an acid usually begins with an “H” (e.g. HCl). Acetic acid (CH3COOH) is an exception because it ends in “H” An acid is a substance that releases H+ ions in an aqueous solution An aqueous solution is a solution that contains water. HCl  H+ + Cl- HS HNO3 HCl HF H2SO4

Exceptions!!! C3H8 CH3 C8H18 CH4 C & H only – are NOT acids!!!

(misleading solutions) Examples ACIDS EXCEPTIONS (misleading solutions) HNO3 H3PO4 HCl CH3 CH4 C3H8 NOTE: any “H” combined with carbon by itself is usually an exception and not considered an acid (called hydrocarbons)

A base is a substance that releases OH- ions in an aqueous solution. Most cleaners (soaps and detergents) are bases They have a bitter taste Red litmus paper turns blue

The formula for a base usually ends with an “OH” (e. g. NaOH) The formula for a base usually ends with an “OH” (e.g. NaOH). Ammonia (NH3) is an exception) Example: NaOH  Na+ + OH- KOH LiOH NaOH Mg(OH)2 NH3

Exceptions!!! C2H5OH CH3OH C2H4(OH)2 Alcohols – are NOT bases!!! **When OH is found at the end of the formula but attached to a carbon and hydrogen it is an alcohol Alcohols – are NOT bases!!!

(misleading solutions) Examples BASES EXCEPTIONS (misleading solutions) NaOH LiOH Mg(OH)2 C2H5OH CH3OH CH3COOH NOTE: any “OH” combined with a carbon and a hydrogen together is an alcohol

INDICATORS Litmus paper is a type of indicator (USED TO DETECT ACIDS OR BASES) Litmus paper is a type of indicator (thin strip of paper that is dipped into a solution) 2 Types: Blue Litmus Paper Red Litmus Paper ACIDS – Turn blue litmus paper red BASES – Turn red litmus paper blue BB

Salts are neutral and have no effect on litmus paper A salt is a substance produced by the chemical bonding of a metallic ion and a nonmetallic ion (other than H+ and OH-). The ions may be polyatomic. Salts enhance the flavour of food. The best known salt is table salt (NaCl) They are often used to change the physical properties of various solutions by lowering the freezing points or raising the boiling points Salts are neutral and have no effect on litmus paper Ions formed by the dissociation of salts play and important role in the metabolism of living organisms

Covalently Bonded Compounds CCl4 PCl3 CF4 CO2 2 non-metals are NOT salts!!!

(misleading solutions) Examples SALTS EXCEPTIONS (misleading solutions) MgCl2 NH4Cl KI PCl3 CCl4 NOTE: these exceptions just have to be memorized

TESTERS: Where do you think these solutions belong? ACIDS BASES SALTS TESTERS: Where do you think these solutions belong? 1. H3PO4 4. HI 2. C8H18 5. MgCl2 3. Ca(OH)2 6. KOH

Summary: Properties of Acids, Bases and Salts

SUMMARY: Remember!! Electrolytic solutions- conduct electricity (acids, bases and salts) They have free ions in aqueous solution Also remember: tap water is electrolytic (free ions!...think of “hard water”) versus distilled water (no free ions) Non-electrolytic solutions – do not conduct electricity (100% pure distilled water, pure alcohols, 2 non-metal compounds)