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Chapter 19 “Acids, Bases, and Salts”. electrolytes. Properties of Acids & Bases!. ACIDS. BASES. electrolytes. sour taste. bitter taste. turn litmus red. turn litmus blue. react with metals to form H 2 gas. don’t react w/metals. slippery feel. “clean” feel.
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electrolytes Properties of Acids & Bases! ACIDS BASES • electrolytes • sour taste • bitter taste • turn litmus red • turn litmus blue • react with metals to form H2 gas • don’t react w/metals • slippery feel • “clean” feel • vinegar, milk, soda, apples, citrus fruits • ammonia, lye, antacid, baking soda • pH < 7 • pH > 7 • Produce OH– ions in H2O • Produce H+ ions in H2O ChemASAP
Properties • Electrolytes can conduct electricity • Can be strong or weak electrolytes in aqueous solution
Acids Affect Indicators Blue litmus paper turns red in contact with an acid.
Acids React with Active MetalsAcids react with active metals to form salts and hydrogen gas:HCl(aq) + Mg(s)→ MgCl2(aq) + H2(g)How can you tell if the gas produced is hydrogen?
Acids React with Carbonates 2HC2H3O2 + Na2CO3 2NaC2H3O2 + H2O + CO2
Effects of Acid Rain on Marble(calcium carbonate) George Washington: BEFORE George Washington: AFTER
Bases Affect Indicators Red litmus paper turns blue in contact with a base. Phenolphthalein turns purple in a base. Vid properties
H H – + O O Cl Cl H H H H Definitions • Arrhenius - In aqueous solution (when dissolved in water)… • Acidsform hydronium ions (H3O+) (or H+) HCl+ H2O H3O+ + Cl– acid Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Arrhenius said: An acid can be defined as a substance that yields hydrogen ions (H+) when dissolved in water. HCl Pure, dry substance is hydrogen chloride When dissolved in water it’s hydrochloric acid… it breaks into H+ ions & Cl- ions
A base can be defined as a substance that yields hydroxide ions (OH-) when dissolved in water. NaOH sodium hydroxide KOH potassium hydroxide Ba(OH)2 barium hydroxide 2.7
H H – + N O O N H H H H H H H H Definitions Video 1 • Arrhenius - In aqueous solution… • Bases form hydroxide ions (OH-) NH3+ H2O NH4+ + OH- base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
conjugate base conjugate acid Definitions • Brønsted-Lowry • Acidsare proton (H+) donors. • Bases are proton (H+) acceptors. HCl + H2O Cl– + H3O+ acid base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Acids and bases come in pairs • A “conjugate base” is the remainder of the original acid, after it donates it’s proton/hydrogen ion • A “conjugate acid” is the particle formed when the original base gains a proton/hydrogen ion • Indicators are weak acids or bases that have a different color from their original acid and base
O N H O H O O H Definitions H2O + HNO3 H3O+ + NO3– B A CA CB Acid Base Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Acids and bases come in pairs • Amphoteric – a substance that can act as both and acid and base- as water shows Video 2
Definitions • Lewis –same guy who came up with the Lewis-dot structures • Acidsare electron pair acceptors. • Bases are electron pair donors. Lewis base Lewis acid Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Acid Definitions The Arrhenius model of acids and bases was broadened by the Bronsted-Lowry model. The Bronsted-Lowry model was broadened by the Lewis model The Lewis acid-base model is the most general in scope. Lewis acids Bronsted-Lowry Arrhenius acids Ralph A. Burns, Fundamentals of Chemistry 1999, page 483