Acids, Bases, and Salts

Acids, Bases and Salts First established in the 1800’s by Swedish chemist Svante Arrhenius Acids – substances that release H + ions in solution Bases – substances that release OH - ions in solution Salts – substances that release positive and negative ions OTHER than H + and OH - in solution *solution = dissolved in water [aqueous] = (aq) Definitions

Acids, Bases and Salts Properties PropertyACIDSBASES Taste Sour taste Bitter Taste Touch Often “sticky” Often “slippery” Reaction with some metals (Ex. magnesium or zinc) Corrode certain metals to form hydrogen gas No reaction Electrical conductivity Conduct an electric current Indicator tests Cause chemical indicators to change colour Chemical formula Usually has a hydrogen on the left (ex. HCl) Usually has a hydroxide (OH) on the right (ex. NaOH)

Acids, Bases and Salts The ratio of the concentrations of H + to OH - ions in solution is referred to as “Acidity” “Concentration” in chemistry is represented with square brackets Ex: [H + ] = concentration of hydrogen ions Solutions can be Acidic, Basic, or Neutral Acidic: [H + ] > [OH - ] ex: HCl (aq) Basic [H + ] < [OH - ] ex: NaOH (aq) Neutral [H + ] = [OH - ] ex: H 2 O (aq), NaCl (aq) Acidity

The ratio of [H + ] to [OH - ] tells us whether a solution is an acid/base/salt, but how do we know just how acidic or basic a solution is? Chemists use an acidity scale called the pH scale that ranges from 0-14 pH < 7 : acidic pH = 7 : neutral pH > 7 : basic The pH scale is logarithmic (based on powers of 10) so each level increases by 10 times (ex: pH 1 is 10 3 times more acidic than pH 4) Acids, Bases and Salts The pH Scale

Chemical indicators, or “Acid-Base Indicators” are compounds that change colour at various pH’s They are incredibly useful for experimentally determining the pH of unknown solutions Acids, Bases and Salts Chemical Indicators

A) if the compound DOES NOT contain oxygen: i) use “-ic acid“ with the “ide” ion ex: HCl = hydrogen chloride = hydrochloric acid ex: HF = B) if the compound DOES contains oxygen: i) use “-ic acid” if it has an “ate” ion ex: HNO 3 = hydrogen nitrate = nitric acid ex: H 2 SO 4 = ii) use “-ous acid” if it has an “ite” ion ex: HSO 3 = hydrogen sulfite = sulfurous acid ex: HClO = Acids, Bases and Salts Naming Acids Naming Bases/Salts follows the same rules as covered earlier with ionic compounds