Acids and Bases Acids are compounds that produce hydronium ions in water [H3O+] **that have H+ as the cation** Sour taste Reactivity with metals (single replacement) Change blue litmus paper red Bases are compounds that produce hydroxide ions in water [OH-] **that have OH– as the anion** Bitter taste Slippery feel Change red litmus paper blue

Reactions and Strengths Acid-Base interactions when acids react with bases, they “neutralize” each other, producing a “salt” and water reactions can be called “acid-base” or “neutralization” reactions Acid-Base strengths can be described in two ways the concentration of hydronium/hydroxide the ease of formation of hydronium/hydroxide

Concentration of H3O+/OH- The pH scale, ranging from 0 – 14, is related to the concentration of hydronium/hydroxide ions acids have low pH, bases have high pH, and pH 7 is neutral pH is a “logarithmic” scale with each unit represents a 10x change in concentration pH Indicators acids turn litmus paper red [red for “hot”] bases turn litmus paper blue [blue for “base”]

Ease of Formation Strong acids and bases = compounds that fully dissociate in solution Strong acids – hydrochloric and sulfuric acids Strong bases – sodium and potassium hydroxides Weak acids and bases = compounds that partially dissociate in solution Weak acid – carbonic and acetic acids Weak base – ammonia

Buffers A buffer solution resists changes in pH when acids or bases are added to the solution Buffers can be created by mixing a weak acid or weak base and its salt H2CO3 and CaCO3 NH4OH and NH4Cl Buffers work because weak acids and bases are only partially dissociated Thus, they are reversible reactions that are subject to Le Chatlier’s Principle (equilibrium)