2 Properties of Acids and Bases taste sour (vinegar, lemons)aqueous solutions of acids are electrolytescause indicators to change colorsmany metals react with acids to produce H2 gasreact with bases to form a salt and watermost formulas begin with Hbitter taste (soap, unsweetened chocolate)bases are electrolytes in aqueous solutioncause indicators to change colorsfeel slipperyreact with acids to form a salt and wateroften contain OH- , or ammonia NH3
3 Examples The bolded formulas below to STRONG acids and bases Common acidsHClHNO3H2SO4H3PO4HC2H3O2H2CO3Common basesNaOHKOHCa(OH)2LiOHNH3
4 Measuring pHThe pH of a substance can tell us if it’s an acid, a base, or neutral. pH is a measurement of the concentration of hydrogen ions (H+) in a solution. The more hydrogen ions present, the more acidic a substance is.Acids have large amounts of hydrogen ions, and low pH (pH < 7).Bases have small amounts of hydrogen ions, and high pH (pH > 7).
5 Another measurement, pOH, tells use the concentration of hydroxide (OH-) ions in a solution. The more hydroxide ions present, the more basic a substance is.Acids have small amounts of hydroxide ions, and high pOH (pOH > 7).Bases have large amounts of hydroxide ions, and low pOH (pOH < 7).Neutral substances have equal amounts of hydrogen and hydrogen ions (pH = 7, pOH = 7).The pH and pOH of a substance always add up to 14.
7 Practice: Are these solutions acidic, basic, or neutral? pH = NH3Large concentration of OH- ions Small concentration of H+ ionspOH = pH = pOHH2SO4 NaOHLarge concentration of H+ ions HCl
8 Practice: Are these solutions acidic, basic, or neutral? If the pH of a solution is 6, what is its pOH? Is it an acid or base?If the pH of a solution is 4, what is its pOH? Is it an acid or base?If the pOH of a solution is 3, what is its pH? Is it an acid or base?
9 IndicatorsIndicators are substances that change color in solutions of different pHHelp determine approximate pH
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