Classifying Compounds

Acids, Bases & Salts Compounds are classified into 3 categories: Acids Bases Salts

Formulas usually start with “H” Acids Any compound that: Turns blue litmus paper red Tastes sour Reacts with some metals to produce H2 gas Conducts electricity when dissolved in water Produces H+ ions when dissolved in water e.g. HCl hydrochloric acid (stomach acid) H2SO4 sulphuric acid (battery acid) H3C6H5O7 citric acid (lemons, oranges, etc.) HCH3COO acetic acid (vinegar) Also can be written as CH3COOH or HC2H3O2 Formulas usually start with “H”

Formulas usually end with “OH” Bases Any compound that: Turns red litmus paper blue Tastes bitter Feels slippery Conducts electricity when dissolved in water Produces OH- ions when dissolved in water e.g. NaOH sodium hydroxide (drain cleaner) KOH Potassium hydroxide (used in batteries) NH4OH Ammonium hydroxide (household cleaner) Al(OH)3 Aluminum hydroxide (antacid) Formulas usually end with “OH”

Indicators Some dyes can help classify acids and bases; they change different colours in the presence of either acids or bases. These dyes are called INDICATORS ACID BASE e.g. Litmus Red Blue Phenolphthalein Colourless Pink (fuchsia) Bromothymol blue Yellow Blue (See your data booklet for a more detailed listing)

Neutralization reactions When acids react with bases they form salts and water Acid + Base  Water + Salt e.g. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) This is called a NEUTRALIZATION reaction In an neutralization reaction, the properties of the acid and base are lost as water and a salt are formed.

Assignment In Class: Acid / Base Worksheet Homework: Workbook Page 91