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Acids and Bases
Recall
• Acids are compounds that start with hydrogen (H+)– HCl (hydrochloric acid)
– H2SO4 (sulfuric acid)
• Bases are compounds that end with hydroxide (OH-)– NaOH (sodium hydroxide)
– Mg(OH)2 (magnesium hydroxide)
Properties of Acids• Sour tasting
• Turn blue litmus paper red• Electrolytes
• HBr(aq) H+(aq) + Br-
(aq)
• Neutralize bases • HCl(aq) + KOH(aq) KCl(aq) + H2O(l)
• React with metals to produce H2 (g)
• 2HNO3(aq) + Zn(s) H2(g) + Zn(NO3)2(aq)
• React with carbonates to produce CO2
• 2HCl + Na2CO3(s) → 2NaCl(aq) + CO2(aq) + H2O(l)
Common Acids
citric acid carbonic acid
acetic acid sulfuric acid
Properties of Bases• Bitter tasting• Slippery feel
• Turn red litmus paper blue
• Electrolytes • LiOH(aq) Li+(aq) + OH-
(aq)
• Neutralize acids • HCl(aq) + Mg(OH)2(s) MgCl2(aq) + H2O(l)
Common Bases
sodium hydroxidemagnesium hydroxide
sodium bicarbonate ammonia
Arrhenius’ Theory• An acid is a substance that dissociates in water to produce
one or more hydrogen ions (H+)
• A base is a substance that dissociates in water to form one or more hydroxide ions (OH-)
Percent Ionization• Percentage of molecules that form ions in solution
Strong Acids• Ionize completely (>99%) in water• [H+] = [Acid]• High electrical conductivity• Very low pH• The corrosive property of acids is attributed to the
hydrogen ion
Strong Bases
• Ionic hydroxides (NaOH, KOH, Ba(OH)2)
• Ionize completely (>99%) in water
• [OH-] = [Base]
• High electrical conductivity
• Very high pH
Weak Acids
• Percent ionization <50%
• [H+] < [Acid]
• Low electrical conductivity
• pH < 7
• Dilute weak acids are safer to handle and even to eat or drink
• Acetic acid, citric acid, carbonic acid
Weak Bases
• Percent ionization <50%
• Low electrical conductivity
• pH > 7
• Ammonia (NH3), sodium bicarbonate NaHCO3
Practice!
• P. 379 # 2-5,11
• P. 392 #1-4