Success 24/7 Chemistry: Difference Between Acids and Bases
hydroxide ion (OH-)
– formed when a water molecule loses a H+
hydronium ion (H3O+)
– formed when a water molecule gains a H+
H2O + H+  H3O+
+
*H and H3O+ are used interchangeably*
Acids
• taste sour or tart (vinegar, lemons)
• most formulas begin with a H
• aqueous solutions of acids are electrolytes
• pH < 7, pOH > 7
• cause indicators to change colors
• [H3O+] > 1.0 x 10-7, [OH-] < 1.0 x 10-7
• many metals react with acids to produce H2
• produce H3O+ (aka H+) in water solutions
• react with hydroxides to form a salt and
• [H3O+] > [OH-]
water
Bases
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produce OH- in water solutions
bitter taste (soap, unsweetened chocolate)
feel slippery
react with acids to form a salt and water
cause indicators to change colors
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often contain OHbases are electrolytes in aqueous solution
pH>7, pOH <7
[H3O+] < 1.0 x 10-7, [OH-] > 1.0 x 10-7
[H3O+] < [OH-]
Label the following as a property of an acid, a base, or both:
Tastes bitter ________________
[H3O+] > [OH-] _______________
pH = 1.9 ____________________
Formula begins with H ________
Produces OH- in water solutions ___________
Electrolyte in water _____________________
Feels slippery __________________________
Tastes sour ____________________________
Common uses of acids
• HNO3 or HCl are used for etching metals.
• HF is used for etching glass.
Indicators
• Indicators are substances that change color in solutions of different pH.
• Indicators are usually weak acids.
• They are one color in their acid form and a different color in their base form.
HIn  H+ + In• Help determine approximate pH
Phenolphthalein
• colorless in acid
Litmus paper
• blue litmus turns red in acid
Universal indicator (UI)
• mixture of indicators
Bromothymol blue
• yellow in acid
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changes to pink in bases between pH 8.2 – 13.0
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red turns blue in base
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changes into different colors at each pH (rainbow colors)
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green in neutral
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blue in base
A solution has a pH of 9.2. What color would the solution cause each below indicator to turn?
Phenolphthalein ________________
Red Litmus Paper ______________
Blue Litmus Paper ______________
Bromothymol Blue _____________
Types of Acids
Acids can be defined by the number of hydrogen ions they produce when ionizing in a solution.
 Monoprotic acid - contains 1 ionizable hydrogen.
Ex. HCl, HNO3
 Diprotic acid - contains 2 ionizable hydrogens.
Ex. H2SO4
 Triprotic acid - contains 3 ionizable hydrogens.
Ex. H3PO4
Label each acid below as mono, di, or triprotic:
H2C2O4 _________________
HBr _________________
H3PO3 _________________