Chapter 15 Acids and Bases

Sect. 15-1: Properties of Acids and Bases Acids  Have a sour taste  Change the color of acid-base indicators  Some react with metals to produce hydrogen gas (if above hydrogen on activity series)  React with bases to produce a salt and water  Some conduct electric current

Acid nomenclature  Binary acid – contains hydrogen and one other element (hydro- root –ic acid)  Oxyacid – contains hydrogen, oxygen, and one other element (-ate polyatomic ions become –ic acids and – ite polyatomic ions become –ous acids) Common industrial acids  Sulfuric acid – petroleum refining, metallurgy, fertilizer  Nitric acid – explosives, plastics, pharmaceuticals, etc  Phosphoric acid – fertilizer, animal feed, soft drinks  Hydrochloric acid – metal work, cleaning masonry  Acetic acid – used in chemical synthesis

Bases  Taste bitter  Change the color of acid-base indicators  Feel slippery  React with acids to produce a salt and water  Conduct electric current

Arrhenius acid – a chemical compound that increases the concentration of hydrogen ions in aqueous solution Arrhenius base – a substance that increases the concentration of hydroxide ions in aqueous solution

Aqueous solutions of acids  Acid molecules attract water molecules which take the hydrogen (forming hydronium, H 3 O + ) and leave behind an anion  HNO 3 + H 2 O  H 3 O + + NO 3 -

Aqueous solutions of bases  Ionic compound will dissociate to produce cations and hydroxide ions NaOH  Na + + OH -  Alkaline – a solution that is created when a base completely dissociates in water to yield aqueous hydroxide ions  Other bases produce hydroxide ions by reacting with water molecules NH 3 + H 2 O  NH OH -

Strength of acids and bases Strong acid – ionizes completely in aqueous solutions; strong electrolyte Weak acid – acids that are weak electrolytes Strong bases – strong electrolytes Weak bases – produces a relatively low concentration of hydroxide ions in solution

Strong acids Chloric acid Hydrobromic acid Hydrochloric acid Hydroiodic acid Nitric acid Perchloric acid Sulfuric acid

Sect. 15-2: Acid-Base Theories Arrhenius definition of acid/base requires aqueous solutions, but substances act as acid/base at other times as well, so other definitions had to be created (Brønsted- Lowry and Lewis)

Brønsted-Lowry acid – a molecule or ion that is a proton donor (remember, H + is a proton) Brønsted-Lowry base – a molecule or ion that is a proton acceptor HCl + NH 3  NH Cl -  HCl is acting as an acid and NH 3 as a base by B-L definition Brønsted-Lowry acid-base reaction – protons are transferred from one reactant (the acid) to another (the base)

Monoprotic acid – an acid that can donate only one proton per molecule (ex. HCl) Polyprotic acid – an acid that can donate more than one proton per molecule (ex. H 2 SO 4 )  Hydrogen atoms are lost one at a time  Diprotic acid – can donate 2 protons per molecule  Triprotic acid – can donate 3 protons per molecule

Lewis acid – an atom, ion, or molecule that accepts an electron pair to form a covalent bond Lewis base – an atom, ion, or molecule that donates an electron pair to form a covalent bond Lewis acid-base reaction – the formation of one or more covalent bonds between an electron-pair donor and an electron-pair acceptor

Sect. 15-3: Acid-Base Reactions Conjugate base – the species that remains after a Brønsted-Lowry acid has given up a proton  HF + H 2 O  F - + H 3 O +  Since HF is the acid, F - is the conjugate base

Conjugate acid – the species that is formed when a Brønsted-Lowry base gains a proton  HF + H 2 O  F - + H 3 O +  Since water is acting as a base, the H 3 O + is the conjugate acid The base and its conjugate acid are referred to as a conjugate acid-base pair

Strength of conjugate acid/base Strong acids produce weak conjugate bases The stronger a base, the weaker its conjugate acid will be Pg. 471 Proton transfer reactions favor the production of the weaker acid and weaker base

Amphoteric – any species that can react as either an acid or a base  Water acts as base with HCl, but was acid with NH 3

Molecular compounds containing the hydroxyl group (-OH) can either be amphoteric or acidic The more oxygen atoms attached to the atom to which the –OH group is attached, the more acidic it will be due to polarity of the bonds

Neutralization reactions Neutralization – reaction of hydronium ions and hydroxide ions to form water molecules Salt – an ionic compound composed of a cation from a base and an anion from an acid

Acid rain is caused by gases (NO, NO2, SO2, SO3) from industrial processes reacting with water vapor in the air to form acids such as sulfuric and nitric acid Acid rain reacts with marble in statues and buildings, eroding it away