Compounds are classified in different ways

Acids & Bases Classification is based on their chemical composition. Acids & bases are very common. Classification is based on their chemical composition. Acids & bases can be very dangerous! Both can be very corrosive. NEVER try to identify an acid or base by taste or touch!

pH Scale The strength is measured on the pH scale Each decrease of 1 on the pH scale indicates 10x more acidic Ex) pH 4 is ten times more acidic than pH 5 pH 3 is 1000X more acidic than pH6

pH Indicators The pH cannot be determined by sight. Instead, pH is measured by: 1) Chemicals called indicators (change colour based on the solution they are placed in) OR 2) By a pH meter (measures the electrical conductivity of the solution using electrical probes)

pH Indicators Can be used for all pH levels: Litmus paper = most common indicator. Two colours: Blue = basic (>7) and Red = acidic (<7). Universal indicators contain many indicators turn different colours at different pH values can be in liquid form, or on paper strips Can be used for only certain pH levels: Bromothymol blue for pH 6 - 7.6, Phenolphthalein for pH 8.2 - 10 Many natural sources, such as beets and cabbage are also indicators

Acids Chemical formula may help to identify acids. Acids often behave like acids only when dissolved in water. So, acids are often written with (aq) = aqueous Chemical formula usually starts with hydrogen (H). Acids with a carbon usually have the C written first. Ex) HCl(aq) = hydrochloric acid HNO3(aq) = nitric acid CH3COOH(aq) = acetic acid

Sulfuric acid is used in batteries. Naming Acids Sulfuric acid is used in batteries. Hydrogen + …-ide = Hydro…ic acid HF(aq) = hydrogen fluoride = hydrofluoric acid Hydrogen + …-ate = …ic acid H2CO3(aq) = hydrogen carbonate = carbonic acid Hydrogen + …-ite = …ous acid H2SO3(aq) = hydrogen sulphite = sulphurous acid

Bases Chemical formula may help to identify bases. Bases, like acids, often behave like bases only when dissolved in water So, bases are often written with (aq) = aqueous Chemical formula usually ends with hydroxide (-OH). Bases can be gentle or very caustic Examples of common bases NaOH(aq) Mg(OH)2(aq) Ca(OH)2(aq) NH4OH(aq)

Production of Ions Acids & bases can conduct electricity because they release ions in solution. Acids release hydrogen ions, H+(aq) Bases release hydroxide ions OH–(aq)

pH of a solution refers to the concentration of ions it has. Square brackets are used to signify concentration High [H+(aq)] = low pH, very acidic High [OH–(aq)] = high pH, very basic A solution cannot have BOTH high [H+(aq)] & [OH–(aq)] They cancel each other out & form water. This process is called neutralization. H+(aq) + OH–(aq)  H2O( )

Properties of Acids and Bases