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Properties of Acids and Bases. Low pH Sour taste Donate H+ Give off H+ in water Neutralize base Phenolphthalein is colorless Start with H. High pH Bitter taste Slippery Gives off OH- in water Accepts H+ Neutralizes acid Phenolphthalein is pink End with OH. Acids and Bases
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Properties of Acids and Bases • Low pH • Sour taste • Donate H+ • Give off H+ in water • Neutralize base • Phenolphthalein is colorless • Start with H • High pH • Bitter taste • Slippery • Gives off OH- in water • Accepts H+ • Neutralizes acid • Phenolphthalein is pink • End with OH
Acids and Bases • Definitions of Acids and bases • Arrhenius acid– a substance that produces H+ in water • Arrhenius base– a substance that produces OH- in water
Strength of Acids or Bases A strong acid or base is one that completely dissociates or breaks up into ions in solution. A weak acid or base is one that only partially dissociates in solution. Lots of molecules still in solution. Strong acids – HCl, HBr, HI, HNO3, H2SO4, HClO4 Strong bases – LiOH, NaOH, KOH, Ba(OH)2 Strong does not mean concentrated.
Naming Acids: HX, H2X, H3X Acids are named after the negative ion, -X. If –X ends in –ide: Hydro (name of the negative ion) –ic acid HCl hydrochloric acid HBr hydrobromic acid HOH hydrohydroxic acid (water) If the negative ion –X ends in –ate: (name of the negative ion)-ic acid HNO3 nitric acid H2CO3 carbonic acid
Common acids that you should be able to name: H2SO4 sulfuric acid HNO3 nitric acid H3PO4 phosphoric acid HCl hydrochloric acid HC2H3O2 acetic acid HBr hydrobromic acid H2CO3 carbonic acid
Acids that give up 1 H+1 are called monoprotic • Acids that give up 2 H+1 are called diprotic • Acids that give up 3 H+1 are called triprotic • There is an analogy for the bases: mono-, di-, and triprotic, but they are giving up OH-1 instead of H+1
Water can break up or ionize on its own: H2O H+1 + OH-1 or 2H2O H3O+1 + OH-1 Only 1 out of every 10 million water molecules ionizes. Water does not normally conduct electricity, because there are not enough ions in the water to carry the charge. The pH scale is a way of indicating how much of the water has ionized or how many H+1 or OH-1 ions are floating around in the water.
pH Scale 0 6.99 Acid 7.00 Neutral 7.01 14.00 Base
Important Equations • pH = -log [H+1] [H+1] = 10-pH • pOH = -log[OH-1] [OH-1] = 10-pOH • pH + pOH = 14.00 • [H+1] x [OH-1] = 1.00 E-14 • pH or pOH always given to 2 places past decimal • [H+1] or [OH-1] always given to 3 sig figs
To find pH (or pOH) +/- or (-) Log [H+1] (or [OH-1]) If it doesn’t work, do it in reverse order To find [H+1] (or [OH-1]) 10x (This is usually the 2nd log function) +/- pH (or pOH) If it doesn’t work, do it in reverse order
Given any one of the pH, pOH, [H+1] or [OH-1] you should be able to determine the other three, and then predict whether the solution is an acid/base/neutral. pH or pOH is always reported to 2 places past the decimal [H+1] or [OH-1] is always reported to 3 sig figs.