Gr. 10 Academic – Chemistry Mr. Findlay Acid, Base & pH Gr. 10 Academic – Chemistry Mr. Findlay

ACIDS

Properties of Acids Dissolves in water, water soluble Conduct electricity in aqueous solution Corrosive (irritates & burns skin) Taste sour pH less than 7 Turn litmus paper red Release hydrogen ions (H+) in aqueous solution Corrode metals Hydrogen first element in compound  binary acids & oxyacids Reacts with metal  hydrogen gas Reacts with carbonate compounds  CO2 gas

Naming Acids Binary acid – hydrogen + nonmetal Ex. HCl (aq)– hydrochloric acid “hydro” nonmetal “ic” Acid Oxyacid – hydrogen + oxyacid Ex.H2SO4 (aq) – sulfuric acid nonmetal “ic” acid

Practice Naming Acids HBr (aq) H2CO3 (aq) H3P (aq) H3PO4 (aq)

BASES or ALKALI

Properties of Bases Dissolves in water Conduct electricity in aqueous solution Corrosive (irritate & burn skin) Taste bitter Feel slippery pH greater than 7 Turns litmus paper Blue Release hydroxide ions (OH-) in aqueous solution Do not corrode metals

Naming Bases Metal + hydroxide ion For example: NaOH NH4OH Ca(OH)2 Mg(OH)2 *Note: not all bases will end in hydroxide

Acid-Base Indicators Substances that change colour in acids or basic solutions Can be used to make classify an unknown solution as an acid or a base We look for changes to make a positive identification

Dissociation of Water

pH scale & the ions in solution

pH scale pH means “power of hydrogen” Measurement is related to number of hydrogen ions in solutions Indicates how acidic or basic a solution is pH only determined when aqueous pH scale is based on a logarithmic scale

Reading pH scale pH less than 7 is Acidic The lower the pH, the more acidic pH = 7 is Neutral pH more than 7 is Basic The higher the pH, the more basic

Lemon Juice is _______ times more acidic than milk. Baking Soda is _______ times more basic than blood. Stomach Acid (pH 2) is _______ times more acidic than seawater.

Acids & Bases in Food

Testing for pH: acid-base indicator Litmus Paper – plant extract (red/blue) dried on strips of paper. Litmus changes Blue = Base Litmus changes Red = Acid Does not change colour = Might be Neutral Universal Indicator – chemical that changes colour through wide range of pH pH meter – instrument that precisely measures pH of solution

pH of common substances using Litmus Paper

Universal Indicator

pH Meter Test voltage of electrolyte Converts voltage to pH Very cheap & accurate Must be calibrated with buffer solution