Acids and bases

Properties of acids & bases

15-1 objectives List 5 general properties of aqueous acids and bases Name common binary acids and oxyacids List 5 common industrial and laboratory acids and give 2 properties of each Define Arrhenius acids and bases Explain the difference between strong and weak acids and bases 4/24/2017

Properties of Acids Taste sour Change the color of pH indicators (turn blue litmus paper red) React with active metals to produce hydrogen gas React with bases to produce salts and water Conduct an electric current 4/24/2017

Properties of Bases Taste bitter Change the color of acid-base indicators (turn red litmus paper blue) Feel slippery React with acids to produce salts and water Conduct an electric current 4/24/2017

Commonly Used Acids Sulfuric acid (H2SO4) dehydrating agent; batteries; metals, paper; dyes, paints & detergents Nitric acid (HNO3) stains proteins yellow; very smelly; explosives Phosphoric acid (H3PO4) fertilizer; ceramics; detergents; flavoring Hydrochloric acid (HCl) “pickling” metals; food processing; pools; cleaning masonry Acetic acid (CH3COOH) smelly; vinegar; freezes at 17oC; plastics; fungicide 4/24/2017

HNO3(l) + H2O(l)  H3O+(aq) + NO3-(aq) Arrhenius Acid & Bases Arrhenius acid – increases the concentration of hydrogen ions in aqueous solution HNO3(l) + H2O(l)  H3O+(aq) + NO3-(aq) The H3O+ ion is called the hydronium ion Arrhenius base – increases the concentration of hydroxide ions in aqueous solutions 4/24/2017

Strong Acids Strong acids ionize completely in aqueous solutions and are strong electrolytes Examples: H2SO4 HClO4 HCl HNO3 HBr HI Do a few examples of showing this ionization process behind this. Demonstrate how the hydronium ion is formed. 4/24/2017

Weak Acids Do not ionize completely and are weak electrolytes Examples: H3PO4 CH3COOH H2CO3 H2S HCN Clip These equations will go both ways. 4/24/2017

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Strong Bases A strong base completely dissociates in water to produce OH- ions Solutions are called alkaline Examples: NaOH KOH 4/24/2017

Weak Bases Weak bases do not dissociate completely in solution Example: NH3 C6H5NH2 (aniline) Clip 4/24/2017

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Acid-Base Theories

15-2 Objectives Define and recognize Brønsted-Lowry acids and bases Define a Lewis acid and a Lewis base Name compounds that are acids under the Lewis definition but are not acids under the Brønsted-Lowry definition 4/24/2017

Brønsted-Lowry Acids A molecule or ion that is a proton donor is Brønsted-Lowry acid Example: HCl dissolved in ammonia HCl dissolved in water H2O dissolved in ammonia Acids donate protons - Complete these three examples by writing out the equations. 4/24/2017

Brønsted-Lowry Bases A molecule or ion that accepts a proton is a Brønsted-Lowry base Example: HCl dissolved in ammonia Bases are proton acceptors 4/24/2017

HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq) Monoprotic Acids Monoprotic acids can donate only one proton Example: HCl(g) + H2O(l)  H3O+(aq) + Cl-(aq) 4/24/2017

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Polyprotic Acids Polyprotic acids can donate more than one proton Example: H2SO4(l) + H2O(l)  H3O+(aq) + HSO4-(aq) HSO4-(aq) + H2O(l)  H3O+(aq) + SO42-(aq) This is a diprotic acid (2 ionizations) 4/24/2017

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Lewis Acids and Bases An atom, ion, or molecule that accepts an electron pair to form a covalent bond is a Lewis acid An atom, ion, or molecule that donates an electron pair to form a covalent bond is a Lewis base 4/24/2017

Acid-base reactions

15-3 Objectives Describe a conjugate acid, conjugate base, and amphoteric compound Explain the process of neutralization Explain how acid rain damages marble surfaces 4/24/2017

Amphoteric A molecule or ion that can be classified as an acid or a base. Ex HSO4- 4/24/2017

Conjugate Acids & Bases The species that remains after a Brønsted-Lowry acid has given up a proton is the conjugate base of that acid. Example: 4/24/2017

Conjugate Acids & Bases The species that is formed when a Brønsted-Lowry base gains a proton is the conjugate acid of that base. Example: 4/24/2017

Brønsted-Lowry acid-base reactions are equilibrium systems (can occur both forward and reverse) and involve two acid-base pairs known as conjugate acid-base pairs. 4/24/2017

Strength of Conjugate Acids and Bases The stronger the acid is the weaker its conjugate base The stronger the base, the weaker its conjugate acid Students will read page 470 to be able to explain this to me. 4/24/2017

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Neutralization Reactions Are reactions between hydronium ions and hydroxide ions to form water Another product is a salt – a cation from an acid and an anion from a base 4/24/2017